91562-10 AC1Fundamentals IG ED2 PR1 Web

A

Edition 2 91562-10

Ba

sic

Ele

ctr

icity a

nd

Ele

ctr

on

ics

AC

1 F

un

da

me

nta

ls

by

Instructor’s Guide

Ê>X5è>Æ7ÀË

3091562100307

SECOND EDITION

First Printing, July 2003

Copyright March, 2003 Lab-Volt Systems, Inc.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,

or transmitted in any form by any means, electronic, mechanical, photocopied, recorded, or

otherwise, without prior written permission from Lab-Volt Systems, Inc.

Information in this document is subject to change without notice and does not represent a

commitment on the part of Lab-Volt Systems, Inc. The Lab-Volt

F.A.C.E.T.®

software and

other materials described in this document are furnished under a license agreement or a

nondisclosure agreement. The software may be used or copied only in accordance with the terms

of the agreement.

ISBN 0-86657-228-7

Lab-Volt

and F.A.C.E.T.®

logos are trademarks of Lab-Volt Systems, Inc.

All other trademarks are the property of their respective owners. Other trademarks and trade

names may be used in this document to refer to either the entity claiming the marks and names or

their products. Lab-Volt System, Inc. disclaims any proprietary interest in trademarks and trade

names other than its own.

Lab-Volt License Agreement By using the software in this package, you are agreeing to

become bound by the terms of this License Agreement,

Limited Warranty, and Disclaimer. This License Agreement constitutes the complete

agreement between you and Lab-Volt. If you do not agree

to the terms of this agreement, do not use the software.

Promptly return the F.A.C.E.T. Resources on Multimedia

(CD-ROM) compact discs and all other materials that are

part of Lab-Volt's F.A.C.E.T. product within ten days to

Lab-Volt for a full refund or credit. 1. License Grant. In consideration of payment of the license

fee, which is part of the price you paid for this Lab-Volt

product, Lab-Volt, as Licensor, grants to you, the Licensee, a

nonexclusive, nontransferable license to use this copy of the

CD-ROM software with the corresponding F.A.C.E.T. Lab-

Volt reserves all rights not expressly granted to the Licensee. 2. Ownership. As the Licensee, you own the physical media

on which the CD-ROM is originally or subsequently recorded

or fixed, but Lab-Volt retains title to and ownership of the

software programs recorded on the original compact disc and

any subsequent copies of the CD-ROM, regardless of the

form or media in or on which the original and other copies

may exist. This license is not a sale of the original software

program of Lab-Volt's CD-ROM or any portion or copy of it. 3. Copy Restrictions. The CD-ROM software and the

accompanying materials are copyrighted and contain

proprietary information and trade secrets of Lab-Volt.

Unauthorized copying of the CD-ROM even if modified,

merged, or included with other software or with written

materials is expressly forbidden. You may be held legally

responsible for any infringement of Lab-Volt's intellectual

property rights that is caused or encouraged by your failure to

abide by the terms of this agreement. You may make copies

of the CD-ROM solely for backup purposes provided the

copyright notice is reproduced in its entirety on the backup

copy. 4. Permitted Uses. This CD-ROM, Instructor's Guide, and all

accompanying documentation is licensed to you, the

Licensee, and may not be transferred to any third party for

any length of time without the prior written consent of Lab-

Volt. You may not modify, adapt, translate, reverse engineer,

decompile, disassemble, or create derivative works based on

the Lab-Volt product without the prior written permission of

Lab-Volt. Written materials provided to you may not be

modified, adapted, translated, or used to create derivative

works without the prior written consent of Lab-Volt. 5. Termination. This agreement is effective until terminated.

It will terminate automatically without notice from Lab-Volt

if you fail to comply with any provisions contained herein.

Upon termination you shall destroy the written materials,

Lab-Volt's CD-ROM software, and all copies of them, in part

or in whole, including modified copies, if any.

6. Registration. Lab-Volt may from time to time update the

CD-ROM. Updates can be made available to you only if a

properly signed registration card is filed with Lab-Volt or an

authorized registration card recipient. 7. Miscellaneous. This agreement is governed by the laws of

the State of New Jersey.

Limited Warranty and Disclaimer This CD-ROM software has been designed to assure correct

operation when used in the manner and within the limits

described in this Instructor's Guide. As a highly advanced

software product, it is quite complex; thus, it is possible that if

it is used in hardware configurations with characteristics other

than those specified in this Instructor's Guide or in

environments with nonspecified, unusual, or extensive other

software products, problems may be encountered by a user. In

such cases, Lab-Volt will make reasonable efforts to assist the

user to properly operate the CD-ROM but without

guaranteeing its proper performance in any hardware or

software environment other than as described in this

Instructor's Guide. This CD-ROM software is warranted to conform to the

descriptions of its functions and performance as outlined in

this Instructor's Guide. Upon proper notification and within a

period of one year from the date of installation and/or

customer acceptance, Lab-Volt, at its sole and exclusive

option, will remedy any nonconformity or replace any

defective compact disc free of charge. Any substantial

revisions of this product, made for purposes of correcting

software deficiencies within the warranty period, will be

made available, also on a licensed basis, to registered owners

free of charge. Warranty support for this product is limited, in

all cases, to software errors. Errors caused by hardware

malfunctions or the use of nonspecified hardware or other

software are not covered. LICENSOR MAKES NO OTHER WARRANTIES OF ANY KIND

CONCERNING THIS PRODUCT, INCLUDING WARRANTIES

OR MERCHANTABILITY OR OF FITNESS FOR A

PARTICULAR PURPOSE. LICENSOR DISCLAIMS ALL

OBLIGATIONS AND LIABILITIES ON THE PART OF

LICENSOR FOR DAMAGES, INCLUDING BUT NOT LIMITED

TO SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT

OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE

PRODUCT LICENSED UNDER THIS AGREEMENT.

Questions concerning this agreement and warranty and all

requests for product repairs should be directed to the Lab-Volt

field representative in your area.

LAB-VOLT SYSTEMS, INC.

P.O. Box 686

Farmingdale, NJ 07727

Attention: Program Development

Phone: (732) 938-2000 or (800) LAB-VOLT

Fax: (732) 774-8573

Technical Support: (800) 522-4436

Technical Support E-Mail: [email protected]

THIS PAGE IS SUPPOSE TO BE BLANK

i

Table of Contents

Section 1 – Workstation Inventory and Installation............................................................... 1-1

Inventory of Workstation ........................................................................................................ 1-1

Minimum Computer Requirements.................................................................................... 1-1

Equipment and Supplies..................................................................................................... 1-1

Equipment Installation ............................................................................................................ 1-1

Software Installation ............................................................................................................... 1-1

Section 2 – Introduction to F.A.C.E.T Curriculum................................................................ 2-1

Getting Started ........................................................................................................................ 2-2

Screen Buttons ........................................................................................................................ 2-3

F.A.C.E.T Help Screens and Resources.................................................................................. 2-4

Internet Access ........................................................................................................................ 2-5

Instructor Annotation Tool...................................................................................................... 2-5

Student Journal........................................................................................................................ 2-5

Assessing Progress .................................................................................................................. 2-6

Real-Number Questions and Answers .................................................................................... 2-8

Recall Values in Text ............................................................................................................ 2-10

Safety .................................................................................................................................... 2-11

Section 3 – Courseware ............................................................................................................. 3-1

Unit 1 – The AC Waveform Generator.................................................................................... 3-1

Exercise 1 – AC Waveform Generator Familiarization.......................................................... 3-3

Exercise 2 – Generator Impedance ......................................................................................... 3-6

Unit 2 – AC Measurements ..................................................................................................... 3-11

Exercise 1 – AC Amplitude Measurement............................................................................ 3-13

Exercise 2 – Measuring With an Oscilloscope ..................................................................... 3-17

Exercise 3 – Measuring and Setting Frequency.................................................................... 3-20

Exercise 4 – Phase Angle...................................................................................................... 3-24

Unit 3 – Inductance.................................................................................................................. 3-29

Exercise 1 – Inductors........................................................................................................... 3-31

Exercise 2 – Inductors in Series and in Parallel.................................................................... 3-36

ii

Unit 4 – Inductive Reactance .................................................................................................. 3-49

Exercise 1 – Inductive Reactance ......................................................................................... 3-50

Exercise 2 – Series RL Circuits ............................................................................................ 3-57

Exercise 3 – Parallel RL Circuits .......................................................................................... 3-62

Unit 5 – Transformers ............................................................................................................. 3-71

Exercise 1 – Transformer Windings ..................................................................................... 3-73

Exercise 2 – Mutual Inductance............................................................................................ 3-78

Exercise 3 – Transformer Turns and Voltage Ratios ............................................................ 3-81

Exercise 4 – Transformer Secondary Loading...................................................................... 3-87

Unit 6 – Capacitance................................................................................................................ 3-99

Exercise 1 – Capacitors....................................................................................................... 3-101

Exercise 2 – Capacitors in Series and in Parallel................................................................ 3-105

Unit 7 – Capacitive Reactance .............................................................................................. 3-113

Exercise 1 – Capacitive Reactance ..................................................................................... 3-114

Exercise 2 – Series RC Circuits .......................................................................................... 3-121

Exercise 3 – Parallel RC Circuits........................................................................................ 3-126

Unit 8 – Time Constants ........................................................................................................ 3-135

Exercise 1 – RC Time Constants ........................................................................................ 3-137

Exercise 2 – RC and RL Wave Shapes ............................................................................... 3-142

Appendix A – Pretest and Posttest Questions and Answers ................................................. A-1

Appendix B – Faults and Circuit Modifications (CMs) .........................................................B-1

Appendix C – Board and Courseware Troubleshooting....................................................... C-1

iii

Introduction

This Instructor Guide is divided into three sections and the appendices. It provides a unit-by-unit

outline of the Fault Assisted Circuits for Electronics Training (F.A.C.E.T) curriculum.

Section 1 – Workstation Inventory and Installation contains a list and description of

equipment and materials required for all units in this course of study as well as installation

instructions.

Section 2 – Introduction to F.A.C.E.T Curriculum provides a description of the courseware

structure, instructions on getting started with the multimedia presentation, and an explanation of

student-progress assessment methods.

Section 3 – Courseware includes information that enables the instructor to gain a general

understanding of the units within the course.

♦ The unit objective

♦ Unit Fundamentals questions and answers

♦ A list of new terms and words for the unit

♦ Equipment required for the unit

♦ The exercise objectives

♦ Exercise Discussion questions and answers

♦ Exercise Procedure questions and answers

♦ Review questions and answers

♦ CMs and Faults available

♦ Unit Test questions and answers

♦ Troubleshooting questions and answers (where applicable)

Appendices include the questions and answers to the Pretest and Posttest plus additional specific

information on faults and circuit modifications (CMs).

Please complete and return the OWNER REGISTRATION CARD included with the CD-

ROM. This will assist Lab-Volt in ensuring that our customers receive maximum support.

iv

THIS

SECTION 1 – WORKSTATION INVENTORY

AND INSTALLATION

THIS

AC1 Fundamentals Section 1 – Workstation Inventory and Installation

1-1

SECTION 1 – WORKSTATION INVENTORY AND INSTALLATION

Inventory of Workstation

Use this section to identify and inventory the items needed.

Minimum Computer Requirements 100% compatible Windows

®PC with Windows98 second edition or newer, NT, 2000, Me or XP;

Pentium class CPU, (Pentium II or newer); 126 MB RAM; 10 GB HDD; CD-ROM drive; SVGA

monitor and video card capable of 32-bit color display at 1024 x 768 resolution and sound

capabilities.

Equipment and Supplies The following equipment and supplies are needed for AC1 Fundamentals:

Quantity Description

1 F.A.C.E.T. base unit

1 AC 1 FUNDAMENTALS circuit board

1 Multimeter

1 Oscilloscope, dual trace

1 Generator, sine wave

1 Student Workbook

1 Instructor Guide

Equipment Installation

To install the hardware, refer to the Tech-Lab (minimum version 6.x) Installation Guide.

Software Installation

Third Party Application Installation

All applications and files that the courseware launches, or that are required for the course should

be installed before the courseware. Load all third party software according to the manufacturers'

directions. Install this software to the default location and note that location. (Alternatively, you

can install this software to a different location that you designate.) Remember to register all

software as required.

No third-party software is required for this course.

Installation of Courseware and Resources

To install the courseware and resources, refer to the Tech-Lab (minimum version 6.x) and

Gradepoint 2020 (minimum version 6.x) Installation Guide.

AC1 Fundamentals Section 1 – Workstation Inventory and Installation

1-2

SECTION 2 – INTRODUCTION TO F.A.C.E.T

CURRICULUM

THIS

AC1 Fundamentals Section 2 – Introduction to F.A.C.E.T Curriculum

2-1

SECTION 2 – INTRODUCTION TO F.A.C.E.T CURRICULUM

Overview F.A.C.E.T curriculum is multimedia-based courseware. The curriculum gives students hands-on

experience using equipment and software closely associated with industry standards. It provides

students with opportunities for instruction in academic and technical skills.

All courses are activity-driven curricula. Each course consists of several units containing two or

more exercises. Each unit begins with a statement explaining the overall goal of the unit (Unit

Objective). This is followed by Unit Fundamentals. Next is a list of new terms and words then

the equipment required for the unit. The exercises follow the unit material. When students

complete all the exercises, they complete the Troubleshooting section and take the Unit Test.

The exercises consist of an exercise objective, exercise discussion, and exercise procedures. The

Exercise Conclusions section provides the students with a list of their achievements. Every

exercise concludes with Review Questions. Available circuit modifications (CMs) and faults are

listed after the review questions. Additional specific information on CMs and faults is available

in Appendix B.


2-2

Getting Started

Desktop

After the Tech-Lab System is installed, the TechLab icon appears on the desktop.

1. Click on the TechLab icon.

2. The student clicks on LOGON and selects his or her name.

3. The student enters his or her password and clicks on OK. (If he or she is creating a password,

four alphanumeric characters must be entered. The system will ask for the password to be

entered again for verification. Keep a record of the students' passwords.)

4. The previous two steps are repeated until all members of the student team have logged on.

Click on Complete and then Yes.

5. When the Available Courses menu appears, students click on the course name.

6. A window with the name of the course and a list of units for that course appears. Students

click on the unit name. The unit title page appears and the students are ready to begin.

Selecting Other Courses and Exiting the Courseware

1. Clicking on Exit when in a unit returns the student to the list of units for that course.

2. If students wish to select another unit, they click on it.

3. If students wish to exit F.A.C.E.T, they click on the X symbol in the upper right corner.

4. If students wish to select another course, they click on the Course Menu button. The

Available Courses menu screen appears. They may also exit F.A.C.E.T from this screen by

clicking on the LOGOFF button.


2-3

Screen Buttons

If you click on the F.A.C.E.T logo on the top right of the unit title page the About screen

appears. It acknowledges the copyright holder(s) of video and/or screen-capture material used in

the topic.

The Menu button calls these menus:

when on an exercise menu screen, it calls the Unit Menu.

when on an exercise screen, it calls the Exercise Menu.

when on a unit screen, it calls the Unit Menu.

The Bookmark button marks the current screen. A student can click on the button at any time in

the lesson. The second time the student clicks on the button, the page displayed when the button

was first clicked will return to the screen. Any bookmarks used during a lesson are not saved

when the student logs out of the lesson.

The Application Launch button opens third-party software.

Click on the Resources button to view a pop-up menu. The pop-up menu includes access to a

calculator, a student journal, new terms and words, a print current screen option, the Lab-Volt

authored Internet Website, and a variety of F.A.C.E.T help screens.

The Help button aids students with system information. On certain screens the Help button

appears to be depressed. On these screens, clicking on the Help button will access Screen Help

windows (context-sensitive help).

The Internet button opens an Internet browser. Students will have unrestricted access to all

search engines and web sites unless the school administration has restricted this usage.

Use the Exit button to exit the course.

The right arrow ⇒ button moves you forward to the next screen.

The left arrow ⇐ button moves you backward to the previous screen.


2-4

F.A.C.E.T Help Screens and Resources

There are three ways to access F.A.C.E.T help screens and other resources.

System Help Students access System Help by clicking on the Help button at the bottom of the screen when the

button does not appear to be depressed. The menu selections access a variety of system help,

navigation, and information windows.

Screen Help On certain screens, the Help button appears to be depressed. On these screens, clicking on the

Help button will access Screen Help windows. This is information specific to the content of that

particular screen.

Resources Students click on the Resources button to access the following windows.

Calculator

F.A.C.E.T 32-Bit Microprocessor Help

F.A.C.E.T Analog Communications Setup Procedure

F.A.C.E.T Digital Communications Help

F.A.C.E.T Electronics and Troubleshooting Help

F.A.C.E.T Fiber Optic Communications Help

F.A.C.E.T Math Help

Internet Link

New Terms and Words

Print Current Page

Student Journal


2-5

Internet Access

There are two ways for students to access the Internet:

The Internet button opens an Internet browser. Students have unrestricted access to all search

engines and websites unless the school administration has restricted this usage.

The Resources button pops up a menu that includes access to the Lab-Volt

authored Internet website. If students wish to access this site when they are not in

the lesson, then they must go to http://learning.labvolt.com.

NOTE: The Lab-Volt Internet site does not have content-filtering

software to block access to objectionable or inappropriate

websites.

Instructor Annotation Tool

The annotation tool gives the instructor the ability to add comments or additional information

onscreen. Refer to the Tech-Lab and GradePoint 2020 Installation Guide for detailed

information.

Student Journal

The student journal is an online notebook that each student can access while they are logged into

TechLab. The journal allows students to share notes with other students in their workgroups.

When used in conjunction with GradePoint 2020, the instructor may post messages, review, edit,

or delete any journal note.


2-6

Assessing Progress

Assessment Tools

Student assessment is achieved in several ways:

♦ Exercise questions

♦ Unit tests

♦ Pretest and Posttest

♦ Troubleshooting questions

Exercise and Troubleshooting Questions

Throughout the unit material, exercise discussion, exercise procedure, and troubleshooting

sections there are several types of questions with instant feedback. These questions occur in the

following formats:

♦ Multiple choice

♦ True-false

♦ Real-number entry

In most cases, when your students encounter a question set, they must answer these questions

before continuing. However, there are cases where students may progress to the next screen

without answering the questions. Lab-Volt recommends that you encourage your students to

complete all questions. In this way, students reinforce the material that's presented, verify that

they understand this material, and are empowered to decide if a review of this material is

required.

Review Questions

At the end of each exercise, there are review questions. The student receives feedback with each

entry. Feedback guides the student toward the correct answer.

Unit Tests

A unit test appears at the end of each unit. The test consists of 10 multiple-choice questions with

the option of having feedback. The Tech-Lab System defaults to no feedback, but the instructor

can configure the test so that students receive feedback after taking the test. You can randomize

questions in the unit test. Use the Tech-Lab Global Configurator to make feedback available,

randomize questions, and select other configuration options if desired. Refer to the Tech Lab

Quick-Start Guide for detailed information.


2-7

Pretest and Posttest

Every course includes a pretest and a posttest. These are multiple choice tests. Refer to the Tech

Lab Quick-Start Guide for detailed information on how to record student competency gains.

Grading

Student grades are based on exercise questions, troubleshooting questions, a unit test, and a

posttest. The default weighting value of the unit test and the threshold for passing the unit test

can be adjusted by using the Global Configurator of the Tech-Lab System. Refer to the Tech Lab

Quick-Start Guide for detailed information.

Student Progress and Instructor Feedback

Unit progress is available through the Unit menu. The Progress window allows the instructor and

student to view the percentage of the unit completed, number of sessions, and time spent on that

unit. The Progress window shows whether the Unit Test was completed. If the test was

completed, it indicates whether the student passed based on the scoring criteria.


2-8

Real-Number Questions and Answers

Throughout F.A.C.E.T courses students may encounter real-number questions such as the one

shown below. Answers to real-number questions are graded correct if they fall within an

acceptable tolerance range.

The answer to the question posed in the illustration above does not involve a recall value from a

previous question. It appears in the Instructor Guide (IG) as shown in the box below.

The information in the IG tells you where the question is located and the range of acceptable

answers. In this case, the acceptable answers fall within the range of the nominal answer plus or

minus 5 percent tolerance: (15 ± 5%).

Location: Exercise Procedure page:

se1p1, Question ID: e1p1a

VS = Vdc

Recall Label for this Question: V1

Nominal Answer: 15.0

Min/Max Value: (14.25) to (15.75)

Value Calculation: 15.000

Correct Tolerance Percent = true

Correct Minus Tolerance = 5

Correct Plus Tolerance = 5

This is the name the computer uses internally

to identify the input value. In this case, 14.5

will be stored under the name V1.

NOTE: The recall value V1 is not the same as

the voltage V1. The recall label does not

appear onscreen.

In this case, the answer to this question is not

based on a value recalled from a previous

question. Therefore, the Value Calculation is

equal to the Nominal Answer.

The word "true" tells you that the tolerance is

calculated as a percent.

e1p1 stands for

Exercise 1 Procedure screen 1

The computer

saves this input

value so that it can

be recalled for use

in later questions.


2-9

A second example (shown below) illustrates an answer that the computer grades using a value

recalled from a previous question.

When a real-number question is based on a recall value from a previous question, the Min/Max

Value shown in the Instructor Guide is based upon a calculation using the lowest and highest

possible recall value. It represents the theoretical range of answers that could be accepted by the

computer. (It is not the nominal answer plus or minus the tolerance.)

To find the actual range of answers that the computer will accept onscreen, you must use the

actual recall value (14.5 in this example) in your calculations; see below.

NOTE: After four incorrect answers, students will be prompted to press <Ins> to insert the

correct answer if this feature has been enabled in the configuration settings. When the question is

based on a value recalled from a previous question, answers obtained using the Insert key may

not match the nominal answers in this guide.

Location: Exercise Procedure page:

se1p5, Question ID: e1p5c

IT = mA

Recall Label for this Question: I1

Nominal Answer: 9.091 *Min/Max Value: (6.477) to (11.93)

Value Calculation: #V1#/1650*1000




Since the value for #V1# is 14.5, the

computer will accept answers in the

following range as correct:

14.5/1650*1000 ± 25% or

8.79 ± 25% or

6.59 to 10.99

This calculated range is different from the

Min/Max Value shown in the IG, which

was based upon a calculation using the

lowest and highest possible recall value.

Any letter enclosed in "#" signs refers to a

recall value from a previous question.


2-10

Recall Values in Text

Sometimes numbers displayed on screen are values recalled from input on previous screens.

Because these numbers are recall values, they will change for each student.

The Instructor Guide lists the recall label in place of a number in this question.

The value of 10

was recalled

from a previous

screen.

Location:Exercise Procedure page: se1p11, Question ID: e1p11c

IR2 = VR2/R2

= #V4#/3.3 kΩ

= mA

Recall Label for this Question: I1


Min/Max Value: (2.489) to (3.164)

Value Calculation: #V4#/3.3




This is a

recall label

for a value

recorded in a

previous

question.

The correct

answer will

depend on the

value the student

recorded in the

previous question.


2-11

Safety

Safety is everyone’s responsibility. All must cooperate to create the safest possible working

environment. Students must be reminded of the potential for harm, given common sense safety

rules, and instructed to follow the electrical safety rules.

Any environment can be hazardous when it is unfamiliar. The F.A.C.E.T computer-based

laboratory may be a new environment to some students. Instruct students in the proper use of the

F.A.C.E.T equipment and explain what behavior is expected of them in this laboratory. It is up to

the instructor to provide the necessary introduction to the learning environment and the

equipment. This task will prevent injury to both student and equipment.

The voltage and current used in the F.A.C.E.T Computer-Based Laboratory are, in themselves,

harmless to the normal, healthy person. However, an electrical shock coming as a surprise will

be uncomfortable and may cause a reaction that could create injury. The students should be made

aware of the following electrical safety rules.

1. Turn off the power before working on a circuit.

2. Always confirm that the circuit is wired correctly before turning on the power. If required,

have your instructor check your circuit wiring.

3. Perform the experiments as you are instructed: do not deviate from the documentation.

4. Never touch “live” wires with your bare hands or with tools.

5. Always hold test leads by their insulated areas.

6. Be aware that some components can become very hot during operation. (However, this is not

a normal condition for your F.A.C.E.T. course equipment.) Always allow time for the

components to cool before proceeding to touch or remove them from the circuit.

7. Do not work without supervision. Be sure someone is nearby to shut off the power and

provide first aid in case of an accident.

8. Remove power cords by the plug, not by pulling on the cord. Check for cracked or broken

insulation on the cord.


2-12

SECTION 3 – COURSEWARE

SECTION 3 – COURSEWARE

THIS

AC1 Fundamentals Unit 1 – The AC Waveform Generator

3-1

UNIT 1 – THE AC WAVEFORM GENERATOR

UNIT OBJECTIVE

Operate a basic ac waveform generator by using equipment provided.

UNIT FUNDAMENTALS

Location: Unit Fundamentals page: sf4, Question ID: f4a

Is the waveform shown an ac or dc waveform?

a. ac

b. dc


Does this ac waveform (square wave) display four complete cycles of a repeating pattern?

a. yes

b. no

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-2

NEW TERMS AND WORDS

alternating current (ac) - a flow of electricity that first increases to maximum, then decreases to

zero, reverses polarity, and reaches maximum in the opposite direction.

waveform - the shape of an electric wave as the amplitude is graphed over time.

amplitude - the level, or magnitude, of an alternating voltage or current.

cycle - one complete alternation of an ac current or voltage.

frequency (f) - the number of complete cycles in one second of alternating voltage or current;

measured in hertz (Hz).

impedance (Z) - the total opposition a circuit offers to the flow of alternating current at a given

frequency.

ac waveform generator - an electronic device that produces ac voltage of a desired frequency,

wave shape, and amplitude.

EQUIPMENT REQUIRED

F.A.C.E.T. base unit

AC 1 FUNDAMENTALS circuit board

Multimeter

Oscilloscope, dual trace

Generator, sine wave


3-3

Exercise 1 – AC Waveform Generator Familiarization

EXERCISE OBJECTIVE

Operate an ac waveform generator by using equipment provided. Verify results by observing

generator waveforms on the oscilloscope.

EXERCISE DISCUSSION

Location: Exercise Discussion page: se1d2, Question ID: e1d2a

Suppose the range of control is set to X100 and the frequency control is set to 20. The output

frequency is

a. 200 Hz

b. 2000 Hz

c. 20 kHz


Look at the generator symbols on the AC 1 FUNDAMENTALS circuit board. Is the waveform

generator internal or external?

a. internal generator

b. external generator

EXERCISE PROCEDURE

Location: Exercise Procedure page: se1p1, Question ID: e1p1a

While observing the oscilloscope, increase the generator frequency control. Does the number of

cycles displayed increase or decrease as the frequency is increased?

a. increase

b. decrease


3-4

REVIEW QUESTIONS

Location: Review Questions page: se1r1, Question ID: e1r1

1. The controls that adjust frequency on an ac generator are the frequency and

a. range controls.

b. amplitude controls.

c. function controls.

d. vertical controls.


2. When the range (multiplier) control of a generator is set to X10 and the frequency control is

set to 20, the output frequency is

a. 2000 Hz.

b. 20 Hz.

c. 200 Hz.

d. 20,000 Hz.


3. The amplitude control on an ac generator is usually labeled

a. MULTIPLIER.

b. FUNCTION.

c. RANGE.

d. LEVEL.


4. Which statement is not characteristic of a typical ac generator?

a. All are capable of generating ac waveforms.

b. All can vary the frequency of the waveform produced.

c. All can vary the amplitude of the waveform produced.

d. All are capable of generating a dc waveform.


5. When the range (multiplier) control of a generator is set to X1K and the frequency control is

set to 10, the output frequency is

a. 1000 Hz.

b. 10 kHz.

c. 100 Hz.

d. 1.0 kHz.


3-5

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-6

Exercise 2 – Generator Impedance

EXERCISE OBJECTIVE

Determine the output impedance of an ac waveform generator. Verify results with an

oscilloscope.

EXERCISE DISCUSSION


If RL decreased in value from 100Ω to 50Ω, would the output voltage across

RL increase or decrease?

a. increase

b. decrease


VOPEN CIRCUIT = Vpk-pk

Recall Label for this Question: None


Min/Max Value: (9.9) to (10.1)






To measure the generator output impedance, adjust RL so that the loaded generator output

voltage is half of the open circuit voltage output. Is the output load resistance (RL) equal to the

internal generator resistance (RS)?

a. yes

b. no


3-7

EXERCISE PROCEDURE


5. Connect the channel 1 (X10) probe across R1 and R2. Do R1 and R2 represent the generator's

load (RL)?

a. yes

b. no


RL = Ω



Min/Max Value: (35) to (65)





REVIEW QUESTIONS


1. The load (RL) equals the output impedance (RS) of the generator when the

a. loaded output voltage equals the open circuit output voltage.

b. loaded output voltage is half of the open circuit output voltage.

c. open circuit output voltage is half of the loaded output voltage.

d. loaded output voltage is twice the open circuit output voltage.


2. The loaded output voltage of a generator is always

a. greater than the open circuit voltage.

b not dependent on the open circuit voltage.

c. equal to the open circuit voltage.

d. less than the open circuit voltage.


3-8


3. A 50Ω load resistor is connected to a generator with an open circuit voltage of 10 Vpk-pk and

an output impedance of 50Ω. The generator's output voltage is

a. 10 Vpk-pk.

b. 5 Vpk-pk.

c. 20 Vpk-pk.

d. 3.3 Vpk-pk.


4. A generator has an open circuit voltage of 10 Vpk-pk and an output impedance of 600Ω. What

value of external load resistor would result in a 5 Vpk-pk output?

a. 600Ω

b. 30Ω

c. 60Ω

d. 300Ω


5. The output impedance of the generator shown is

a. 600Ω.

b. 60Ω.

c. 500Ω.

d. 50Ω.

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-9

UNIT TEST

Depending on configurator settings, these questions may be randomized onscreen.

Location: Unit Test Question page: sut1, Question ID: ut1

Alternating voltage and current differ from direct voltage and current because alternating voltage

and current

a. maintain a constant polarity.

b. change in level and polarity.

c. never change level or polarity.

d. are not measured in volts or amperes.


One complete repetition of an ac waveform is called

a. the amplitude.

b. a cycle.

c. the frequency.

d. polarity.


If a 20 kHz sine wave is needed on the output of an ac generator and the multiplier control is set

to X100, the frequency control should be set to

a. 20.

b. 10.

c. 100.

d. 200.


A generator has an open circuit voltage of 5 Vpk-pk and an output impedance of 50Ω. What

value of external load resistor would result in a 2.5 Vpk-pk output?

a. 50Ω

b. 25Ω

c. 5Ω

d. 500Ω


A 600Ω load resistor is connected to a generator with an open circuit voltage of 20 Vpk-pk and

an output impedance of 600Ω. The generator's output voltage is

a. 20 Vpk-pk.

b. 25 Vpk-pk.

c. 10 Vpk-pk.

d. 6.6 Vpk-pk.


3-10


What type of waveform does not change polarity with time?

a. sine wave

b. square wave

c. dc wave

d. triangle wave


The controls that adjust frequency on an ac generator are the frequency and

a. amplitude controls.

b. multiplier controls.

c. function controls.

d. vertical controls.


When the loaded output voltage of a generator is half of the open circuit output voltage, the

external load is

a. much greater than the output impedance of the generator.

b. twice the output impedance of the generator.

c. half of the output impedance of the generator.

d. equal to the output impedance of the generator.


Which control on a generator determines the type of output waveform?

a. amplitude

b. function

c. range

d. frequency


Which control on a generator adjusts the level of the output waveform?

a. function

b. frequency

c. amplitude

d. range

AC1 Fundamentals Unit 2 – AC Measurements

3-11

UNIT 2 – AC MEASUREMENTS

UNIT OBJECTIVE

Take amplitude, frequency, and phase measurements of ac waveforms by using an oscilloscope.

UNIT FUNDAMENTALS


Which of the following ac instruments can be used to measure the amplitude, frequency, and

phase shift of ac waveforms?

a. multimeter

b. oscilloscope


As in a circle, one complete cycle of a sine wave equals 360 degrees. One fourth of a cycle is

a. 180 degrees.

b. 90 degrees.

c. 270 degrees.

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-12

NEW TERMS AND WORDS

phase angle - the angle of separation between two ac waveforms of identical frequency.

peak-to-peak value - amplitude between opposite peaks of an ac waveform

(Vpk-pk = Vpk x 2).

peak value - maximum amplitude in either polarity of an ac waveform

(Vpk = Vpk-pk/2).

effective value (rms) - an ac value that produces the same heating effect in a resistor as an

equivalent dc value does.

average value (avg) - the value obtained by dividing the sum of a number of quantities by

the number of quantities. For sine waves, Vavg = 0.637 x Vpk.

period - time required for an ac waveform to complete one cycle (T = 1/f).

EQUIPMENT REQUIRED



Multimeter




3-13

Exercise 1 – AC Amplitude Measurement

EXERCISE OBJECTIVE

Measure the amplitude of ac waveforms by using an oscilloscope. Verify results with a

multimeter.

EXERCISE DISCUSSION


If the peak-to-peak value is 15 Vpk-pk, the peak voltage is

a. 15 Vpk.

b. 30 Vpk.

c. 7.5 Vpk.


The rms value of a sine wave measuring 10 Vpk on an oscilloscope is

a. 7.07 Vac.

b. 7.07 Vpk-pk.

c. 7.07 Vpk.


The average value of a sine wave measuring 10 Vpk on an oscilloscope is

a. 6.37 Vpk.

b. 6.37 Vavg.

c. 12.7 Vavg.


Vrms = Vrms



Min/Max Value: (4.351) to (4.529)






3-14

EXERCISE PROCEDURE


Vpk-pk

Vpk = ————= Vpk

2

Recall Label for this Question: Vpk1

Nominal Answer: 3.0






Location: Exercise Procedure page: se1p2, Question ID: e1p2c

Vrms = Vpk x 0.707 = Vrms

Recall Label for this Question: Vrms1

Nominal Answer: 2.1






Location: Exercise Procedure page: se1p2, Question ID: e1p2e

Vavg = Vpk x 0.637 = Vavg

Recall Label for this Question: Vavg1

Nominal Answer: 1.9







3-15


8. Disconnect the X10 probe from the circuit. Turn on the multimeter and set it for ac voltage

measurement. Connect the multimeter across R1, then measure the voltage.

VR1 = Vac

Recall Label for this Question: Vrms2

Nominal Answer: 2.1







9. Compare your multimeter reading of #Vrms2#V with your oscilloscope values, shown above.

The multimeter displays values in

a. peak-to-peak.

b. peak.

c. rms.

REVIEW QUESTIONS


1. The effective value of an ac waveform is the

a. peak-to-peak value.

b. peak value.

c. rms value.

d. average value.


2. The peak value of an ac waveform is

a. twice the peak-to-peak value.

b. half of the peak-to-peak value.

c. 0.707 of the peak-to-peak value.

d. 0.637 of the peak-to-peak value.


3-16


3. The rms value of a sine wave is

a. half of the peak-to-peak value.

b. twice the peak value.

c. 0.637 of the peak value.

d. 0.707 of the peak value.


4. When measuring the peak-to-peak value of an ac waveform on the oscilloscope, measure from

the

a. top of a peak to the bottom of a valley.

b. top of a peak to the top of a valley.

c. bottom of a peak to the top of a valley.

d. bottom of a peak to the bottom of a valley.


5. Most digital multimeters display the

a. peak-to-peak value of a sine wave.

b. peak value of a sine wave.

c. rms value of a sine wave.

d. average value of a sine wave.

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-17

Exercise 2 – Measuring With an Oscilloscope

EXERCISE OBJECTIVE

Measure voltage by using an oscilloscope and determine current and impedance by using Ohm's

law. Verify results with information found in this exercise.

EXERCISE DISCUSSION


The circuit shown uses 10Ω resistor R2 as the current-sensing resistor. If the voltage across R2

is 50 mVpk-pk, what is the circuit current?

I = V/R2 = mApk-pk

Recall Label for this Question: IT

Nominal Answer: 5.0







Placing the oscilloscope input directly across a component, as shown,

a. shorts out R2 and L2.

b. provides an accurate circuit voltage display.


3-18

EXERCISE PROCEDURE


I = mApk-pk



Min/Max Value: (12.04) to (22.36)






VR1 = Vpk-pk


Nominal Answer: 8.0






REVIEW QUESTIONS


1. The oscilloscope measures

a. voltage only.

b. voltage and current only.

c. voltage, current, and impedance.

d. current only.


2. The oscilloscope ground clip and the generator common

a. are independent of one another.

b. are of opposite polarity.

c. are virtually the same point.

d. cannot be connected together.


3-19


3. To measure, with an oscilloscope, the voltage drop across an ungrounded component in a

system with common grounds,

a. place the probe directly across the component being measured.

b. use the ALT-INVERT method.

c. place the probe in series with the component being measured.

d. use the ADD-INVERT method.


4. To measure circuit current with the oscilloscope,

a. use a current-measuring inductor.

b. place the probe in series with the circuit.

c. use a current-sensing resistor.

d. divide the source voltage by the generator impedance.


5. To determine circuit impedance,

a. divide the source voltage by the measured circuit current.

b. measure directly with a multimeter.

c. divide the source voltage by the generator impedance.

d. assume it is always a constant 50.

CMS AVAILABLE

CM 7 TOGGLE

FAULTS AVAILABLE

None


3-20

Exercise 3 – Measuring and Setting Frequency

EXERCISE OBJECTIVE

Measure and set frequency by using an oscilloscope. Verify results with information found in

this exercise.

EXERCISE DISCUSSION


To set the generator frequency to 100 Hz, adjust the frequency control on the generator so that

the period (T) of the waveform trace on the oscilloscope equals

a. 1 ms.

b. 10 ms.

c. 10 µ .


A waveform trace on the oscilloscope has a measured period of 0.7 ms. The frequency is

a. 1.43 kHz.

b. 1.42 Hz.

c. 14.3 kHz.


3-21

EXERCISE PROCEDURE


4. Set the time base control on the oscilloscope to 0.1 ms/div. Adjust the frequency of the

generator for a waveform cycle that is seven divisions wide along the horizontal axis (time axis).

T (period) = ms

Recall Label for this Question: T

Nominal Answer: 0.7







1

f = —— = Hz

T

Recall Label for this Question: f


Min/Max Value: ( 1000) to ( 1858)






6. Compare your calculated value of frequency (#f# Hz) with the frequency read from the dial of

the generator. The two frequencies do not agree. What method do you think results in the closest

setting of the correct frequency?

a. generator dial

b. oscilloscope (period)


3-22

REVIEW QUESTIONS


1. The period (T) of a waveform is

a. equal to the frequency.

b. the reciprocal of the amplitude.

c. the reciprocal of the frequency.

d. unrelated to the frequency.


2. The frequency of a waveform is

a. equal to the period.

b. unrelated to the period.

c. the reciprocal of the period.

d. unrelated to time.


3. What is the period of a 2 kHz sine wave?

a. 2 ms

b. 200 µs

c. 5 ms

d. 500 µs


4. What is the frequency of a sine wave having a period of 250 µs?

a. 4 kHz

b. 2.5 kHz

c. 250 Hz

d. 5 kHz


5. The period is the

a. number of waveform cycles that occur in one second.

b. time it takes a waveform to go from maximum positive value to maximum negative value.

c. time it takes a waveform to complete one cycle.

d. time it takes a waveform to go from maximum positive value to zero amplitude.


3-23

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-24

Exercise 4 – Phase Angle

EXERCISE OBJECTIVE

Measure phase angle by using an oscilloscope. Verify results with information found in this

exercise.

EXERCISE DISCUSSION


Suppose the channel 1 oscilloscope display is adjusted so that one cycle is exactly 8 divisions

wide. What is the phase angle between the two sine waves (use CH 1 as the reference)?

a. 80°

b. 45°


Is the sine wave displayed on CH 2 leading or lagging the reference sine wave displayed

on CH 1?

a. leading

b. lagging

EXERCISE PROCEDURE


6. Make certain the oscilloscope trigger source control is set to CH 1. Switch the vertical mode to

ALT. Set both channel ground references to the center graticule line. Is the phase angle between

the input (CH 1) and output (CH 2) waveforms approximately zero?

a. yes

b. no


7. Slowly turn potentiometer R2 completely counterclockwise (CCW). Did a phase shift occur?

a. yes

b. no


3-25


8. Switch the vertical mode to CH 1 (display CH 1 only), and adjust the time base and variable

time base controls on the oscilloscope so that one cycle of the waveform is exactly 8 divisions.

How many degrees does each horizontal division represent?

a. 80°

b. 45°


Phase angle = (d)(45/div)

= degrees



Min/Max Value: (50.75) to (94.25)






11. Is the output (CH 2) waveform leading or lagging the reference (CH 1) waveform?

a. leading

b. lagging

REVIEW QUESTIONS


1. What waveform is usually used as a reference for measuring phase angle?

a. the output waveform

b. the input waveform

c. the line voltage waveform

d. the oscilloscope calibrator waveform


2. When the reference waveform is 8 divisions wide (horizontally) on the oscilloscope, how

many degrees does each division represent?

a. 90°

b. 80°

c. 45°

d. 36°


3-26


3. What is the phase angle between the two sine waves (use channel 1 as the reference)?

a. 45° lagging

b. 90° leading

c. 45° leading

d. 90° lagging


4. What is the phase angle between the two sine waves (use channel 1 as the reference)?

a. 90° leading

b. 90° lagging

c. 45° leading

d. 45° lagging


5. When you measure phase angle, both waveforms must be

a. of identical frequency.

b. of identical amplitude.

c. square waves.

d. different frequencies.

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-27

UNIT TEST



A sine wave has a period (T) of 1 ms. The frequency is

a. 1 ms.

b. 100 Hz.

c. 1000 Hz.

d. 10 ms.


One complete cycle of a sine wave equals

a. 360°.

b. 270°.

c. 180°.

d. 90°.


The degree of separation between two sine waves of the same frequency is the

a. amplitude.

b. period.

c. phase angle.

d. root mean square.


The time required for an ac waveform to complete one cycle is the

a. amplitude.

b. period.

c. phase angle.

d. root mean square.


The reciprocal value of the period equals the

a. phase angle.

b. peak value.

c. period.

d. frequency.


3-28


Measuring a waveform from the top of a peak to the top of a valley on the oscilloscope

accurately measures

a. peak-to-peak amplitude.

b. peak amplitude.

c. the effective value.

d. the waveform period.


The peak value of a 10 Vpk-pk sine wave is

a. 10.0 Vpk.

b. 5.0 Vpk.

c. 7.07 Vrms.

d. 6.36 Vavg.


The reciprocal value of the frequency equals the

a. frequency.

b. phase angle.

c. period.

d. peak current.


The peak value multiplied by 0.707 is the rms value of

a. sine waves only.

b. sine waves and square waves.

c. square waves only.

d. sine waves and triangle waves.


The oscilloscope directly measures

a. current only.

b. voltage and current.

c. voltage only.

d. voltage, current, and impedance.

AC1 Fundamentals Unit 3 – Inductance

3-29

UNIT 3 – INDUCTANCE

UNIT OBJECTIVE

Describe the effect of inductance on a circuit by using an oscilloscope.

UNIT FUNDAMENTALS


What type of circuit would produce the greatest cemf?

a. dc circuit

b. ac circuit


Which wire configuration would result in the greatest inductance value?

a. coil of wire

b. straight piece of wire


What value of inductance would result in a lower circuit current for any one frequency?

a. 5 mH

b. 10 mH

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-30

NEW TERMS AND WORDS

inductance (L) - one property of a conductor that opposes change in current flow.

counter electromotive force (cemf) - a voltage developed in an inductive circuit by alternating

current. The polarity of this voltage is, at every instant, opposite to that of the applied voltage.

inductor - a conductor, usually a coil of wire, wound to concentrate its magnetic field, which

produces a predicted measure of inductance.

henry (H) - unit of inductance. An inductance of one henry will produce one volt of cemf when

ac current of one ampere at one hertz is applied.

EQUIPMENT REQUIRED



Multimeter




3-31

Exercise 1 – Inductors

EXERCISE OBJECTIVE

Describe the effect an inductor has on dc and ac circuits by using measured values. Verify results

with an oscilloscope and multimeter.

EXERCISE DISCUSSION


If inductance decreases, opposition to current flow will

a. increase.

b. remain the same.

c. decrease.

EXERCISE PROCEDURE


RL3 = Ω

Recall Label for this Question: RL3meas








Idc = mA

Recall Label for this Question: Idcmeas








3-32


VL3dc = Vdc

Recall Label for this Question: VL3meas


Min/Max Value: ( .459) to ( .853)






RL3cal = Ω

Recall Label for this Question: RL3cal


Value Calculation: (#VL3meas#)/(#Idcmeas#/1000)





9. Compare the coil resistance of RL3 (#RL3meas#Ω), measured by using the resistance function

of the multimeter and the calculated coil resistance of RL3cal (#RL3cal#Ω). Based on this

comparison, is inductor L3 producing cemf with constant dc current applied?

a. yes

b. no

* NOTE: Min/Max Values shown are based upon a calculation using the absolute lowest and

highest recall value. By using the actual input in your calculations, you will determine the correct

value.


3-33


Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: Iac








VL3ac = Vpk-pk

Recall Label for this Question: VL3ac

Nominal Answer: 7.5







ZL3 = Ω

Recall Label for this Question: ZL3

Nominal Answer: 595.2 *Min/Max Value: (310.9) to ( 1139)

Value Calculation: #VL3ac#/(#Iac#/1000)






value.


3-34


15. Compare the coil resistance of RL3 (#RL3meas#Ω) and the calculated coil impedance ZL3

(#ZL3#Ω). Based on this comparison, is L3 producing cemf when ac current is applied?

a. yes

b. no


19. Does an increase of inductance increase or decrease circuit current?

a. increase

b. decrease


21. What is the effect of an increase in frequency on circuit current?

a. remains the same

b. decreases

c. increases


25. Does the circuit current lead or lag the inductor voltage?

a. lead

b. lag

REVIEW QUESTIONS


1. When constant dc is applied to an inductor, current flow is opposed by

a. cemf only.

b. coil resistance only.

c. cemf and coil resistance.

d. emf only.


2. When the CM is toggled off and on, what can you conclude about the inductance of L3 based

on the circuit current?

a. The inductance of L3 was reduced in value.

b. Changing the inductance of L3 had no effect on circuit current.

c. The inductance of L3 increased in value.

d. Changing the inductance of L3 decreased the circuit current.


3-35


3. Decreasing the frequency of the signal applied to an inductor

a. decreases current flow.

b. increases cemf.

c. neither increases nor decreases the current.

d. decreases impedance.


4. In an ideal inductor,

a. voltage leads current by 90°.

b. current leads voltage by 90°.

c. voltage lags current by 90°.

d. voltage and current remain in phase.


5. An increase in cemf produced by an inductor is seen as

a. a decrease in voltage drop.

b. an increase in circuit current.

c. an increase in impedance.

d. a decrease in the coil resistance.

CMS AVAILABLE

CM 16 TOGGLE

CM 17 TOGGLE

FAULTS AVAILABLE

None


3-36

Exercise 2 – Inductors in Series and in Parallel

EXERCISE OBJECTIVE

Determine the total inductance of a circuit containing inductors in series and in parallel. Verify

results with an oscilloscope.

EXERCISE DISCUSSION


LT = mH


Nominal Answer: 6.0







What is the total inductance (LT) in the above circuit?

a. 2 mH

b. 4 mH

c. 1 mH


3-37

EXERCISE PROCEDURE


LT = mH


Nominal Answer: 4.7

Min/Max Value: (4.653) to (4.747)






VR2

Iac = ———

R2

= mApk-pk

Recall Label for this Question: Iacc








VL3ac = Vpk-pk

Recall Label for this Question: VL3acc

Nominal Answer: 7.5







3-38


ZL3 = Ω

Recall Label for this Question: ZL33


Value Calculation: #VL3acc#/(#Iacc#/1000)





LT = mH


Nominal Answer: 9.4

Min/Max Value: (9.212) to (9.588)






12. Did adding the inductor in series increase or decrease total circuit inductance (LT)?

a. increase

b. decrease


VR2

Iac = ——— = mApk-pk

R2

Recall Label for this Question: Iac1

Nominal Answer: 7.6








value.


3-39


VLT = Vpk-pk

Recall Label for this Question: VLT


Min/Max Value: (6.272) to (11.65)






ZLT = Ω

Recall Label for this Question: ZLT


Value Calculation: #VLT#/(#Iac1#/1000)





16. Compare your data from the two circuits. Which circuit offers the greatest opposition

(impedance) to current flow for the same signal input (VGEN)?

a. single inductor circuit

b. two-inductor series circuit


LT = mH



Min/Max Value: (2.28 ) to (2.421)







value.


3-40


VR2

Iac = ——

R2

= mApk-pk



Min/Max Value: (11.97) to (22.23)






VL = Vpk-pk

Recall Label for this Question: VL

Nominal Answer: 5.0







ZL = Ω

Recall Label for this Question: ZL


Value Calculation: #VL#/(#Iac2#/1000)






value.


3-41


23. Compare your data from the two circuits. Which circuit offers the greatest opposition

(impedance) to current flow for the same signal input (VGEN)?

a. single inductor circuit

b. two-inductor parallel circuit


24. While observing the oscilloscope, toggle the CM off and on by pressing <CM>. Based on the

circuit's current change, was the new inductor added to the circuit in series or in parallel with L3

and L4?

a. series

b. parallel

REVIEW QUESTIONS


1. The total inductance of inductors in series is

a. determined from the reciprocal method.

b. the sum of the inductor values divided by two.

c. the sum of the inductor values.

d. the reciprocal of the sum of the inductors.


2. The total inductance of inductors in parallel is

a. determined from the reciprocal method.

b. the sum of the inductor values.

c. the sum of the inductor values divided by two.

d. the reciprocal of the sum of the inductors.


3. As more inductors are added in parallel,

a. circuit current increases.

b. impedance increases.

c. circuit current decreases.

d. inductance increases.


3-42


4. As more inductors are added in series,

a. inductance decreases.

b. circuit current increases.

c. circuit current decreases.

d. impedance decreases.


5. Toggle the CM off and on by pressing <CM>. Based on the circuit current change, the unseen

inductor

a. was added in parallel.

b. had no effect on circuit current.

c. was added in series.

d. caused the circuit current to increase.

CMS AVAILABLE

CM 17 TOGGLE

CM 16 TOGGLE

FAULTS AVAILABLE

None


3-43

UNIT TEST



Inductance is the property of a conductor that

a. aids any change in current flow.

b. opposes change in current flow.

c. produces a magnetic field.

d. opposes unchanging current flow.


Increasing the number of turns on an inductor

a. decreases the inductance.

b. increases circuit current.

c. increases the inductance.



When dc is applied to an inductor, the only opposition to current flow is the

a. counter electromotive force (cemf).

b. changing impedance of the inductor.

c. frequency effect on the value of inductance.

d. resistance of the wire in the coil.


Two 10-mH inductors in parallel have a combined inductance of

a. 5.0 mH.

b. 20 mH.

c. 10 mH.

d. 3.3 mH.


A straight piece of wire has relatively little inductance because

a. it does not possess any inductive property.

b. the magnetic field is spread over a large area.

c. cemf is produced only in coils.

d. there is no core.


Increasing the frequency of the signal applied to an inductor

a. increases current flow.

b. increases the inductor impedance.

c. decreases the inductor impedance.

d. decreases the amount of cemf produced.


3-44


Two 7-mH inductors in series have a combined inductance of

a. 7 mH.

b. 3.5 mH.

c. 7.5 mH.

d. 14 mH.


Increasing the number of inductors in series

a. decreases total inductance.


c. increases impedance.

d. decreases cemf.


Increasing the number of inductors in parallel

a. decreases total inductance.

b. decreases circuit current.


d. increases cemf.


The current in an inductor

a. leads the voltage by 45°.

b. leads the voltage by 90°.

c. lags the voltage by 90°.

d. lags the voltage by 45°.


3-45

TROUBLESHOOTING

Location: Troubleshooting page: ttrba2, Question ID: trba2a

Connect the channel 2 oscilloscope probe across R1, which is the output (VR1) of the full-wave

bridge rectifier. Are both alternations of the ac input waveform being rectified to dc pulses atthe

output?

a. yes

b. no

Location: Troubleshooting page: ttrba2, Question ID: trba2c

VR1 = Vdc



Min/Max Value: (6.237) to (7.623)





Location: Troubleshooting page: ttrba3, Question ID: trba3

6. The faulty component is

a. T1 (an open secondary coil).

b. R1 (shorted).

c. D2 (shorted).

d. T1 (an open primary coil).

Location: Troubleshooting page: ttrbb2, Question ID: trbb2a

Connect the channel 2 oscilloscope probe across R1, which is the output (VR1) of the full-wave

bridge rectifier. Are both alternations of the ac input waveform being rectified to dc pulses at the

output?

a. yes

b. no


3-46

Location: Troubleshooting page: ttrbb2, Question ID: trbb2c

VR1 = Vdc



Min/Max Value: (6.237) to (7.623)





Location: Troubleshooting page: ttrbb3, Question ID: trbb3


a. T1 (an open secondary coil).

b. R1 (shorted).

c. D2 (shorted).

d. T1 (an open primary coil).

Location: Troubleshooting page: ttrbc2, Question ID: trbc2a

Connect the channel 2 oscilloscope probe across the output (R1 and R2). Is the output essentially

a constant dc voltage signal with no observable ripple?

a. yes

b. no

Location: Troubleshooting page: ttrbc2, Question ID: trbc2c

4. With a multimeter, mesure the dc voltage of the output (Vo).

Vo = Vdc



Min/Max Value: (17.17) to (23.23)





Location: Troubleshooting page: ttrbc3, Question ID: trbc3


a. CR2 (shorted).

b. CR1 (open).

c. C2 (open or not connected).

d. C1 (open or not connected).


3-47

Location: Troubleshooting page: ttrbd2, Question ID: trbd2a

Connect the channel 2 oscilloscope probe across the output (R1 and R2). Is the output essentially

a constant dc voltage signal with no observable ripple?

a. yes

b. no

Location: Troubleshooting page: ttrbd2, Question ID: trbd2c

4. With a multimeter, mesure the dc voltage of the output (Vo).

Vo = Vdc



Min/Max Value: (17.17) to (23.23)





Location: Troubleshooting page: ttrbd3, Question ID: trbd3


a. CR2 (shorted).

b. CR1 (open).

c. C2 (open or not connected).

d. C1 (open or not connected).

CMS AVAILABLE

None

FAULTS AVAILABLE

Fault 7

Fault 9

Fault 10

Fault 11


3-48

AC1 Fundamentals Unit 4 – Inductive Reactance

3-49

UNIT 4 – INDUCTIVE REACTANCE

UNIT OBJECTIVE

Determine the characteristics of resistive-inductive (RL) circuits by using an oscilloscope and

given information.

UNIT FUNDAMENTALS


If the frequency of the power source (Vac) increases from 1 kHz to 10 kHz, inductive reactance

(XL)

a. increases.

b. decreases.

c. remains the same.

CMS AVAILABLE

None

FAULTS AVAILABLE

None

NEW TERMS AND WORDS

inductive reactance (XL) - the opposition to the flow of alternating current by the inductance of

a circuit. It is measured in ohms.

phasor - a quantity consisting of magnitude and direction used to describe an ac waveform.

EQUIPMENT REQUIRED



Multimeter




3-50

Exercise 1 – Inductive Reactance

EXERCISE OBJECTIVE

Determine inductive reactance (XL) by using calculated and measured values. Verify results

with an oscilloscope.

EXERCISE DISCUSSION


If L1 is decreased from 1 mH to 0.5 mH, inductive reactance

a. increases.

b. decreases.



When a sine wave of 30 kHz is applied to n inductor of 1 mH, inductive reactance is:

a. 5000 ohms.

b. 5.31 x 10 ohms.

c. 188 ohms.


3-51

EXERCISE PROCEDURE


Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: Iaca

Nominal Answer: 5.4







VL3 = Vpk-pk

Recall Label for this Question: VL3a

Nominal Answer: 9.6







XL3 = Ω

Recall Label for this Question: XL

Nominal Answer: 1778.0 ∗Min/Max Value: (928.5) to ( 3401)

Value Calculation: #VL3a#/(#Iaca#/1000)




∗ NOTE: Min/Max Values shown are based upon a calculation using the absolute lowest and


value.


3-52


7. Calculate the value of XL3.

XL3 = 2πfL

= Ω

Recall Label for this Question: XL1


Min/Max Value: ( 1718) to ( 1824)






8. Comparing your values of XL3 from the practical method (#XL#Ω) and the calculated method

(#XL1#Ω), does it appear that either method can be used?

a. yes

b. no


Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: IaL3


Min/Max Value: (12.32) to (22.88)






VL3 = Vpk-pk

Recall Label for this Question: VL3L

Nominal Answer: 5.6







3-53


Does decreasing inductance increase or decrease inductive reactance?

a. increase

b. decrease


VL3

XL3 = ———

Iac

= Ω



Min/Max Value: (414.4) to (769.6)






14. Compare your values of inductive reactance at 60 kHz (#XL#Ω) and at 20 kHz (#XL2#Ω).

Does decreasing the frequency of the applied signal increase or decrease inductive reactance?

a. increase

b. decrease


15. Adjust the frequency of the generator to 60 kHzand VGEN for 8 Vpk-pk. Remeasure the

circuit current (Iac) and voltage drop across L3 (VL3). Calculate XL3 with the generator

amplitude at 8 Vpk-pk.

VL3

XL3 = ———

Iac

= Ω



Min/Max Value: ( 1244) to ( 2310)






3-54


16. Compare your value of inductive reactance at a generator input of 10 Vpk-pk (#XL#Ω) and 8

Vpk-pk (#XL3#Ω). Decreasing the amplitude of the applied signal causes inductive reactance to

a. increase.

b. decrease.

c. remain the same.

REVIEW QUESTIONS

Location: Review Questions page: se1r1, Question ID: e1r1a

1. Locate the INDUCTANCE/INDUCTIVE REACTANCE circuit block on the AC 1

FUNDAMENTALS circuit board. Connect the circuit shown. Adjust VGEN for a 10 Vpk-pk, 60

kHz sine wave.

VL3

XL3 = ——— = Ω

Iac



Min/Max Value: ( 1244) to ( 2310)





Location: Review Questions page: se1r1, Question ID: e1r1c

1. CM 16 alters the value of L3. Remeasure the circuit current (Iac) and voltage drop across L3

(VL3). Calculate XL3 with CM 16 activated.

VL3

XL3 = ——— = Ω

Iac



Min/Max Value: ( 3600) to ( 7478)






3-55


1. Compare your value of inductive reactance before CM 16 was activated (#XL4#Ω) with the

value after CM 16 activated (#XL5#Ω). You conclude that CM 16

a. decreased the inductance.

b. increased the amplitude of VGEN.

c. increased inductance.

d. decreased XL3.


2. A 10 kHz, 12 Vpk-pk sine wave applied to an inductor measuring 1.0 mH has an inductive

reactance (XL) of

a. 62.8Ω.

b. 14.1Ω.

c. 590Ω.

d. 7.8 kΩ.


3. Increasing the amplitude of the signal applied to an inductor

a. decreases inductive reactance.

b. has no effect on inductive reactance.

c. increases inductive reactance.

d. decreases circuit current.


4. Inductive reactance increases when

a. frequency increases.

b. inductance decreases.

c. frequency decreases.

d. amplitude increases.


5. The equation used to determine inductive reactance (XL = 2πfL) in this exercise is valid for

a. sine waves and square waves.

b. square waves only.

c. sine waves only.

d. all ac waveforms.


3-56

CMS AVAILABLE

CM 17

CM 16

FAULTS AVAILABLE

None


3-57

Exercise 2 – Series RL Circuits

EXERCISE OBJECTIVE

Determine characteristics of series RL circuits by using calculated and measured values. Verify


EXERCISE DISCUSSION


The total value of resistance (RT) in the series RL circuit shown is 1700Ω (RT = R1 + R2 + R3).

The total value of inductive reactance (XLT) is

a. 600Ω.

b. 2500Ω.

c. 1000Ω.

Location: Exercise Discussion page: se2d4, Question ID: e2d4c

__________

Z = √RT2 + XLT

2 = Ω



Min/Max Value: ( 2932) to ( 3114)






______________

Vac = √VRT2 + VXLT

2

= V









3-58


θ = degrees



Min/Max Value: (47.52) to (58.08)





EXERCISE PROCEDURE


IT = VR2 /R2 = mApk-pk

Recall Label for this Question: IT10


Min/Max Value: (10.16) to (15.24)






VL3

XL3 = ——— = Ω

IT









3-59


VGEN

Z = ———— = Ω

IT

Recall Label for this Question: Z10


Min/Max Value: (550.9) to ( 1023)






8. Compare your value of Z (#Z10#Ω) with the individual values of RT and XLT. Can

impedance (Z) be determined by directly adding RT and XLT?

a. yes

b. no


VL3 = Vpk-pk

Recall Label for this Question: VL3d

Nominal Answer: 7.5







VR1 = Vpk-pk

Recall Label for this Question: Vr1d

Nominal Answer: 5.9







3-60


12. Compare the applied value of VGEN with VR1 and VL3. In a series RL circuit, does VGEN

equal the sum of the individual component drops?

a. yes

b. no


13. Observe the phase angle (θ) between the circuit current (circuit current and VR2 have

identical phase) and VGEN. Use VGEN as a reference. Does the circuit current lead or lag the

applied generator voltage?

a. lead

b. lag


15. Observe the phase angle (θ) between the circuit current and VGEN. Use VGEN as a

reference. Did the added series inductor increase or decrease the phase angle between VGEN and

circuit current?

a. decrease

b. increase

REVIEW


1. While observing the oscilloscope, toggle the CM off and on by clicking on <CM>. Based on

your observation of the circuit current, you conclude that adding a series inductor to this circuit

a. increased circuit current.

b. decreased circuit impedance.

c. had no effect on circuit current.

d. decreased circuit current.


2. An RL circuit containing three series-connected inductors with reactances of 200Ω, 500Ω, and

1500Ω has a total inductive reactance of

a. 131Ω.

b. 2.5 kΩ.

c. 2.2 kΩ.

d. 150Ω.


3-61


3. In a series RL circuit, the applied generator voltage equals the

a. square root of the sum of the squares of the individual voltage drops across the

individual resistors and inductors.

b. sum of the voltage drops across the individual resistive components.

c. square root of the sum of the squares of the individual voltage drops across the inductors.

d. sum of the voltage drops across the individual resistors and inductors.


4. The total inductive reactance of inductors in series is

a. determined from the reciprocal formula.

b. the sum of the individual reactances.

c. the sum of the individual inductances.

d. the reciprocal of the individual inductances.


5. The phase angle between the applied generator and circuit current in a series RL circuit is

a. 90°.

b. 180°.

c. greater than 90°.

d. less than 90°.

CMS AVAILABLE

CM 17 TOGGLE

CM 16 TOGGLE

FAULTS AVAILABLE

None


3-62

Exercise 3 – Parallel RL Circuits

EXERCISE OBJECTIVE

Determine characteristics of parallel RL circuits by using calculated and measured values. Verify


EXERCISE DISCUSSION


XL1 x XL2

XLT = —————— = Ω

XL1 + XL2

Recall Label for this Question: XLTP








Calculate total circuit curent (IT).

________

IT = √IR2 + IL

2 = mApk-pk



Min/Max Value: (16.49) to (17.51)






3-63

EXERCISE PROCEDURE



Recall Label for this Question: ITpar

Nominal Answer: 8.2







Does IT equal the sum of the individual branch currents in a parallel RL circuit?

a. yes

b. no


Does the added parallel inductor cause total inductive reactance (XLT) to increase or decrease?

a. increase

b. decrease



Recall Label for this Question: ITpar1








10. Compare your value of circuit impedance with one inductor (# 3/(ITpar/1000)#Ω) to the

value of circuit impedance with two inductors of (#3/(ITpar1/1000)Ω). Did the added parallel

inductor cause circuit impedance to increase or decrease?

a. increase

b. decrease


3-64

REVIEW QUESTIONS


1. Based on your observation of the circuit, you conclude that adding a parallel inductor to the

RL circuit

a. decreased circuit current.

b. increased circuit impedance.

c. decreased circuit impedance.

d. had no effect on the circuit.


2. An RL circuit consisting of two parallel-connected inductors with reactances of 750Ω and 75

kΩ has a total inductive reactance of

a. 75.75 kΩ.

b. 743Ω.

c. 770Ω.

d. 75 kΩ.


3. The circuit current of a parallel RL circuit equals the square root of the sum of the

a. squares of the resistive and inductive branch voltages.

b. resistive and inductive branch voltages.

c. squares of the resistive and inductive branch currents.

d. resistive and inductive branch currents.


4. The total inductive reactance of inductors in parallel is

a. the sum of the individual inductances.


c. determined from the reciprocal formula.

d. the reciprocal of the individual inductances.


5. As inductance decreases in a parallel circuit,

a. phase angle increases.

b. circuit current decreases.

c. circuit impedance increases.

d. inductive reactance increases.


3-65

CMS AVAILABLE

CM 17 TOGGLE

FAULTS AVAILABLE

None


3-66

UNIT TEST



Inductive reactance depends on

a. amplitude and frequency.

b. inductance and amplitude.

c. frequency and inductance.

d. inductance only.


Inductive reactance

a. lies on the negative portion of the Y axis of the X-Y coordinate system.

b. is equal to 2πfL.

c. is added to resistance to yield total circuit impedance.

d. is multiplied by resistance to yield total circuit impedance.


What inductive reactance results when a 7 Vpk-pk, 20 kHz sine wave is applied to an inductor of

10 mH (XL = 2πfL)?

a. 9.48 kΩ b. 5.95 kΩ c. 1.256 kΩ d. 4.17 MΩ


Adding inductors in series to an RL circuit a. decreases inductive reactance.

b. increases phase angle.

c. increases circuit current.

d. decreases circuit impedance.


Adding inductors in parallel to an RL circuit

a. increases inductive reactance.


c. increases circuit impedance.



3-67


The equation XL = 2πfL is valid for

a. all ac waveforms.


c. sine waves and square waves.

d. sine waves only.


As inductors are added in series,

a. circuit impedance decreases.


c. inductive reactance increases.

d. inductive reactance decreases.


The current flowing through an inductor

a. leads the voltage across the inductor by 90º.

b. is in phase with the voltage across the inductor.

c. lags the voltage across the inductor by 90º.

d. lags the voltage across the inductor by 45º.


When inductors are added in parallel,

a. inductive reactance decreases.


c. inductive reactance increases.

d. circuit impedance increases.


Increasing the frequency of the signal applied to an inductor


b. has no effect on inductive reactance.


d. decreases the voltage drop across the inductor.


3-68

TROUBLESHOOTING


3. To ensure proper circuit operation (performance check), measure the output voltage across L2

(VL2) as a result of the input voltage (VGEN).

VL2 = Vpk-pk


Nominal Answer: 4.6








a. L2 (open).

b. L1 (reduced in value).

c. L2 (shorted).

d. R1 (increased in value).


3. To ensure proper circuit operation (performance check), measure the output voltage across L4

(VL4) as a result of the input voltage (VGEN).

VL4 = Vpk-pk


Nominal Answer: 5.1








a. L4 (open).

b. L3 (short).

c. R1 (decreased in vlaue).



3-69

CMS AVAILABLE

None

FAULTS AVAILABLE

Fault 7

Fault 8


3-70

AC1 Fundamentals Unit 5 – Transformers

3-71

UNIT 5 – TRANSFORMERS

UNIT OBJECTIVE

Describe the transfer of electrical energy from one circuit to another by mutual inductance.

UNIT FUNDAMENTALS


In the figure, which coil, or winding, is the primary?

a. L1

b. L2


What type of core is this transformer wound on?

a. air

b. ferrite

c. iron

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-72

NEW TERMS AND WORDS

mutual inductance - the ability of one coil to induce voltage into another coil in close proximity

by way of a fluctuating magnetic field.

transformer - a device used to couple energy from one circuit to another through mutual

inductance.

primary - a transformer winding connected to the source voltage.

secondary - a transformer winding connected to the load.

coupling - the transfer of energy from one circuit to another.

tap - a fixed electrical connection to a specified position on the winding of a transformer.

autotransformer - a transformer consisting of one winding that acts as both primary and

secondary.

step-down transformer - a transformer whose applied primary voltage is greater than the

secondary voltage.

step-up transformer - a transformer whose secondary voltage is greater than the applied primary

voltage.

ferrite - a nonconductive, powered, compressed, magnetic, iron-based material.

EQUIPMENT REQUIRED



Multimeter




3-73

Exercise 1 – Transformer Windings

EXERCISE OBJECTIVE

Determine the coil resistances of a transformer by using a multimeter. Verify results with

information found in this exercise.

EXERCISE DISCUSSION


A resistance measurement with a multimeter between the primary and secondary windings

measures

a. a short circuit.

b. 100Ω.

c. an open circuit.

EXERCISE PROCEDURE


2. Locate the symbol for transformer T1 in the TRANSFORMER circuit block. What type of

core is indicated by the symbol?

a. iron

b. ferrite

c. air


3. The secondary winding is the winding on the right. Is the secondary of transformer T1 tapped?

a. yes

b. no


3-74


RP = Ω

Recall Label for this Question: RP


Min/Max Value: (185.5) to (344.5)






RS = Ω

Recall Label for this Question: RS








6. Compare your measured values of primary winding resistance (#RP#Ω) and secondary

winding resistance (#RS#Ω) of transformer T1. Which winding has more turns (assuming that

both are made from the same type of wire)?

a. primary

b. secondary


7. Measure the resistance between the primary and secondary windings with a multimeter (leads

1 and 3 or 2 and 4). Does an open circuit exist between the primary and secondary windings?

a. yes

b. no


3-75


RS1 = Ω

Recall Label for this Question: RS1








RS2 = Ω

Recall Label for this Question: RS2








10. Based on your resistance measurements of RS1 (#RS1#Ω) and RS2 (#RS2#Ω), and assuming

the entire secondary winding is made of the same type of wire, is the tap located near the top,

center, or bottom of the secondary winding?

a. top

b. center

c. bottom


3-76

REVIEW QUESTIONS


1. The winding of a transformer to which an external voltage is applied is called the

a. secondary.

b. tap.

c. primary.

d. core.


2. Which symbol indicates a transformer with a ferrite core?

a. transformer a

b. transformer b

c. transformer c

d. transformer d


3. A transformer tap may appear

a. on the secondary winding only.

b. anywhere along a winding.

c. at the center of a winding only.

d. on the primary winding only.


4. In a regular transformer, no electrical connection exists between the

a. primary leads.

b. secondary leads.

c. primary and secondary windings.

d. applied voltage and the primary.


5. The resistance in a transformer winding is related to the

a. mutual inductance.

b. gauge of the wire.

c. transformer core.

d. tap.


3-77

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-78

Exercise 2 – Mutual Inductance

EXERCISE OBJECTIVE

Demonstrate mutual inductance by using a typical transformer. Verify results with an

oscilloscope.

EXERCISE DISCUSSION

No Questions

EXERCISE PROCEDURE


4. Press and hold down switch S1 while you measure the dc voltage across the secondary

winding (VS). Use a multimeter. Is there any dc voltage across the secondary with a constant dc

applied to the primary?

a. yes

b. no


6. While observing the oscilloscope display, press and release the switch several times. Did

pulsing the dc supply on the primary cause a voltage pulse to be induced across the secondary?

a. yes

b. no


9. Observe the display on the oscilloscope. Does the ac voltage on the primary induce a voltage

in the secondary?

a. yes

b. no


3-79

REVIEW QUESTIONS


1. Voltage induced from the primary winding to the secondary is caused by

a. coil resistance.

b. mutual inductance.

c. constant dc current.

d. a center tap.


2. Voltage is induced into the secondary

a. only when a sine wave is applied to the primary.

b. only when the primary current is constant.

c. whenever constant dc is applied to the primary.

d. whenever the primary current is changing.


3. A fluctuating magnetic field surrounding the primary

a. induces a voltage in the secondary.

b. induces a voltage in the transformer core.

c. is produced by constant dc current.

d. is produced by a tapped secondary.


4. An ac waveform applied to the primary winding induces a voltage in the secondary because ac

a. is unchanging.

b. is changing.

c. does not produce a changing current.

d. maintains constant amplitude.


5. When a dc source connected to the primary of a transformer is pulsed on and off by a switch,

voltage is induced into the secondary because

a. the pulsing dc current causes the magnetic field to fluctuate.

b. only dc current causes a voltage to be induced into the secondary.

c. the switch causes the primary and secondary to be directly connected.

d. the pulsing dc current prevents mutual inductance.


3-80

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-81

Exercise 3 – Transformer Turns and Voltage Ratios

EXERCISE OBJECTIVE

Determine the turns and voltage ratios of a transformer by using calculated and measured values.

Verify results with an oscilloscope.

EXERCISE DISCUSSION


Suppose a transformer has a primary voltage of 90V and a secondry voltage of 30V. The turns

ratio (and voltage ratio) would be

a. 10:1

b. 3:1

c. 30:1


Applying a 100V sine wave to the primary (leads 1 to 2) of this step-down transformer results in

what secondary output if you measure from the center tap to one end (leads 3 to 5 or 4 to 5) of

the secondary winding?

a. 50V

b. 100V

c. 25V


3-82

EXERCISE PROCEDURE


3. Using an oscilloscope, measure the voltage across the entire secondary winding (VS).

VS = Vpk-pk

Recall Label for this Question: VS1

Nominal Answer: 4.0







4. Comparing the input voltage (VGEN = 8 Vpk-pk) to your measured secondary voltage (VS =

#VS1# Vpk-pk), is transformer T1 a step-up or step-down transformer?

a. step-up

b. step-down


VP VGEN

Voltage Ratio = =

VS VS

=

Recall Label for this Question: VRatio1

Nominal Answer: 2.0 ∗Min/Max Value: (1.492) to (2.943)

Value Calculation: # 8 / VS1 #






value.


3-83


VS = V

Recall Label for this Question: VS2

Nominal Answer: 2.0







VP VGEN

Voltage Ratio = =

VS VS

=


Nominal Answer: 2.0







8. Compare your calculated voltage ratio (#VRatio1#, VGEN = 8 Vpk-pk) with your other

calculated voltage ratio (#VRatio2#, VGEN = 4 Vpk-pk). Did the voltage ratio remain the same

or did it change when the primary voltage was changed from 8 Vpk-pk to 4 Vpk-pk?

a. changed

b. remained the same


VTAP = Vpk-pk

Recall Label for this Question: VTAP

Nominal Answer: 2.0







3-84


10. Compare your measured value of VTAP (#VTAP# Vpk-pk) with your previously measured

value of VS (#VS1# Vpk-pk). Is the secondary winding tapped at the center?

a. yes

b. no


VP VGEN

Voltage Ratio = =

VTAP VTAP

=



Value Calculation: # 8 / VTAP #





12. What voltage ratio would produce the smallest secondary voltage for an 8 Vpk-pk primary

voltage?

a. 2:1

b. 4:1



value.


3-85

REVIEW QUESTIONS


1. A transformer with 1800 turns of wire on the primary and 900 turns on the secondary has a

turns ratio of

a. 1:2.

b. 1:3.

c. 2:1.

d. 3:1.


2. The voltage ratio equals the

a. current ratio.

b. turns ratio.

c. power ratio.

d. inverse of the turns ratio.


3. The secondary voltage measured from the center tap

a. increases the voltage ratio of a step-down transformer.

b. decreases the voltage ratio of a step-down transformer.

c. decreases the current ratio of a step-down transformer.

d. increases the voltage ratio of a step-up transformer.


4. The voltage ratio is independent of the

a. turns ratio.

b. current ratio.

c. secondary voltage.

d. amplitude of the applied signal.


5. A transformer having a greater voltage across the secondary than it has across the primary is

a(n)

a. step-down transformer.

b. iron core transformer.

c. step-up transformer.

d. autotransformer.


3-86

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-87

Exercise 4 – Transformer Secondary Loading

EXERCISE OBJECTIVE

Determine the effect of secondary loading by using a typical transformer. Verify results with an

oscilloscope.

EXERCISE DISCUSSION


A transformer with a voltage and turns ratio of 10:1 has a secondary current (IS) of 100 mA.

What is the primary (IP) current?

a. 1000 mA

b. 10 mA

c. 1 mA


An ideal step-down transformer with a voltage ratio of 10:1 has input power (PP) equal to 500

mW. What is the power out (PS)?

a. 50 mW

b. 5000 mW

c. 500 mW

EXERCISE PROCEDURE


IP = VR1 /R1

= µApk-pk

Recall Label for this Question: IPNL


Min/Max Value: (141.5) to (424.5)






3-88


IP = VR1 /R1= mApk-pk

Recall Label for this Question: IPL

Nominal Answer: 1.9







5. Compare your calculated values of primary current with no load across the secondary

(#IPNL# µApk-pk) to the primary current with a 1 kΩ load (#IPL# mApk-pk). Did the primary

current increase or decrease with the addition of a load (R2) across the secondary?

a. increase

b. decrease


8 Vpk-pk

VGENrms = x 0.707 = Vrms

2

Recall Label for this Question: VGENrms


Min/Max Value: (2.745) to (2.915)






3-89


VR1 pk-pk x 0.707

IPrms =

2 x R1

= mArms

Recall Label for this Question: IPrms


Min/Max Value: (0.476) to (0.884)






PP = mW

Recall Label for this Question: PP


Value Calculation: #VGENrms#*#IPrms#





VR2 pk-pk

VR2rms = x 0.707 = Vrms

2

Recall Label for this Question: VR2RMS


Min/Max Value: (0.777) to (1.443)







value.


3-90


14. Determine the secondary rms current.

VR2rms #VR2RMS2#

ISrms = = = mArms

R2 1000

Recall Label for this Question: ISRMS

Nominal Answer: 1.11 ∗Min/Max Value: ( .754) to (1.486)

Value Calculation: #VR2RMS#





PS = VR2rms x Isrms

= mW

Recall Label for this Question: PS

Nominal Answer: 1.232 *Min/Max Value: ( .568) to (2.209)

Value Calculation: #VR2RMS#*#ISRMS#





PS

efficiency % = x 100

PP

= %

Recall Label for this Question: %


Value Calculation: (#PS#/#PP#)*100






value.


3-91


17. Your calculated value of efficiency for T1 is #%#%. If T1 were an ideal (perfect)

transformer, would the percentage of efficiency be higher or lower?

a. higher percent

b. lower percent

REVIEW QUESTIONS


1. A transformer is a

a. nonregulating device.

b. self-regulating device.

c. nonconductive device.

d. self-inhibiting device.


2. Adjust VGEN for an 8 Vpk-pk, 1 kHz sine wave. Using the oscilloscope, measure the voltage

drop across R2 (VR2). Convert your peak-to-peak measurement to an rms value.

Vpk-pk x 0.707

VR2rms =

2

= Vrms

Recall Label for this Question: VR2CM


Min/Max Value: (0.581) to (1.079)






3-92


ISrms = mA

Recall Label for this Question: ISCM


Value Calculation: (#VR2CM#/320)*1000





2. The secondary power (PS) of T1 equals

a. 9.4 mW.

b. 2.1 mW.

c. 0.4 mW.

d. 94.0 mW.


3. The current ratio between the primary and secondary equals the

a. voltage ratio.

b. power ratio.

c. inverse of the power ratio.

d. inverse of the voltage ratio.


4. If the load resistance on the secondary increases, the

a. voltage ratio increases.

b. primary current increases.

c. primary current decreases.

d. current ratio increases.



value.


3-93


5. A transformer with 5 mW of power in the primary and 5 mW of power in the secondary has an

efficiency of

a. 50%.

b. 100%.

c. 25%.

d. 10%.

CMS AVAILABLE

CM 5

FAULTS AVAILABLE

None


3-94

UNIT TEST



An inductor can induce a voltage into another inductor in close proximity

a. if the current through the inductor is constant.

b. only if the inductors are wound around an iron core.

c. if the current through the inductor is changing.

d. only if one of the inductors is tapped.


The voltage in the secondary winding of a transformer is caused by

a. mutual inductance.

b. constant dc voltage in the primary.

c. a center tap.

d. the secondary load.


A transformer with 1200 turns on the primary and 12,000 turns on the secondary has a voltage

ratio of

a. 2:1.

b. 10:1.

c. 1:10.

d. 1:2.


A transformer that has a greater voltage across the primary than it has across the secondary is a

a. step-up transformer.

b. ferrite core transformer.

c. power transformer.

d. step-down transformer.


A transformer with a current ratio of 3:1 has a voltage ratio of

a. 3:1.

b. 1:3.

c. 1:1.

d. 1:1.5.


3-95


An iron or ferrite core in a transformer

a. provides a direct electrical connection between the primary and secondary windings.

b. concentrates the magnetic field surrounding the windings.

c. suppresses the magnetic field surrounding the windings.

d. produces a magnetic field.


A tap may appear

a. only at the center of the primary.

b. anywhere on the secondary winding.

c. only at the center of the secondary.

d. anywhere along any winding.


If the load resistance on the secondary decreases, the

a. primary current increases.

b. voltage ratio decreases.

c. primary current decreases.

d. current ratio increases.


A transformer is a self-regulating device because the

a. primary winding is not connected to the secondary.

b. secondary voltage remains constant when the primary voltage changes.

c. primary automatically compensates for changes in the secondary load.

d. secondary current remains constant when the load changes.


In an ideal transformer, the turns ratio equals

a. the current ratio.

b. the power ratio.

c. twice the current ratio.

d. the voltage ratio.


3-96

TROUBLESHOOTING


3. To ensure proper circuit operation (performance check), measure the output voltage across R2

(VR2) as a result of the input voltage (VGEN).

VR2 = Vpk-pk


Nominal Answer: 3.3








a. a shorted turn on the primary.

b. an open turn on the primary.

c. a shorted turn on the secondary.

d. an open turn on the secondary.




VR2 = Vpk-pk


Nominal Answer: 3.3








a. a shorted turn on the primary.

b. an open turn on the primary.

c. a shorted turn on the secondary.

d. an open turn on the secondary.


3-97

CMS AVAILABLE

None

FAULTS AVAILABLE

Fault 4

Fault 5


3-98

AC1 Fundamentals Unit 6 – Capacitance

3-99

UNIT 6 – CAPACITANCE

UNIT OBJECTIVE

Describe the effect of capacitance on a circuit by using an oscilloscope.

UNIT FUNDAMENTALS


A dc voltage source of 25V is applied to a capacitor, and then the voltage source is removed.

What is the charge (voltage) across the capacitor?

a. 0 volts

b. 25 volts


Capacitor C1 is fully charged. What is the voltage drop across R1?

a. 0 volts

b. 15 volts

CMS AVAILABLE

None

FAULTS AVAILABLE

None

NEW TERMS AND WORDS

capacitance (C) - the property of a capacitor to store charge.

capacitor - a device consisting of two conducting surfaces separated by an insulating material

and possessing a predicted amount of capacitance.

farad (F) - unit of measure for capacitance. A farad equals one coulomb of charge stored at a

potential of one volt.

leakage current - a small, undesirable amount of current that flows through the dielectric of a

capacitor.

dielectric - the insulating material between the two plates of a capacitor.


3-100

EQUIPMENT REQUIRED



Multimeter




3-101

Exercise 1 – Capacitors

EXERCISE OBJECTIVE

Describe the effect a capacitor has on dc and ac circuits by using measured values. Verify results

with a multimeter and an oscilloscope.

EXERCISE DISCUSSION


If the value of C1 were increased to 0.9 µF, the circuit current (IC1) would

a. increase.

b. decrease.

c. remain the same.


If the frequency of the signal source were changed to 5 kHz, circuit current (IC1) would

a. increase.

b. decrease.

c. remain the same.

EXERCISE PROCEDURE


5. While monitoring the oscilloscope for voltage across C1, close S1. Does the capacitor charge

up when the dc voltage is applied?

a. yes

b. no


Does the charge on C1 remain even after the dc source is removed?

a. yes

b. no


3-102


9. While monitoring the multimeter display, hold S1 closed for about 15 seconds. Repeat several

times (discharge C1 each time by using S2). Based on the reaction of the multimeter display, was

current flowing while capacitor C1 was charging?

a. yes

b. no


10. Based on the reaction of the multimeter display, did current stop flowing after the capacitor

became fully charged?

a. yes

b. no


Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: Iac

Nominal Answer: 4.5







13. Does the current flowing in the circuit indicate that C3 is passing ac?

a. yes

b. no


15. CM 10 is activated to increase the capacitance of C3 from 0.1 µF to 0.2 µF. While observing

the oscilloscope, toggle the CM off and on by clicking on <CM>. Does an increase in

capacitance increase or decrease circuit current?

a. increase

b. decrease


3-103


16. Monitor the circuit current on the oscilloscope. Increase the generator frequency. Does

increasing the frequency of the applied signal increase or decrease circuit current?

a. decrease

b. increase


18. Observe the phase angle (θ) between the circuit current (VR2) and VC3. Does the

circuit current lead or lag the capacitor voltage?

a. lead

b. lag

REVIEW QUESTIONS


1. A capacitor

a. blocks ac and passes dc.

b. blocks dc and passes ac.

c. passes ac and dc.

d. blocks ac and dc.


2. What can you conclude based on the reaction of the circuit current?

a. The capacitance of C3 increased in value.

b. Changing the capacitance of C3 had no effect on circuit current.

c. The capacitance of C3 decreased in value.

d. Changing the capacitance of C3 increased circuit current.


3. Decreasing the frequency of the signal applied to a capacitor

a. decreases current flow.

b. has no effect on current flow.

c. increases current flow.



3-104


4. In a capacitor,

a. current lags voltage by 90º.

b. current leads voltage by 90º.

c. voltage leads current by 90º.

d. voltage and current remain in phase.


5. A capacitor allows dc current flow

a. only while it is charging.

b. when it is fully charged.

c. only while it is discharging.

d. while it is charging or discharging.

CMs AVAILABLE

CM 10 TOGGLE

CM 9 TOGGLE

FAULTS AVAILABLE

None


3-105

Exercise 2 – Capacitors in Series and in Parallel

EXERCISE OBJECTIVE

Determine total capacitance by using circuits that have capacitors in series and in parallel. Verify


EXERCISE DISCUSSION


What is the total capacitance (CT) of this circuit?

a. 5 µF

b. 10 µF

c. 2.5 µF


What is CT?

a. 0.8 µF

b. 8.0 µF

c. 80. µF


3-106

EXERCISE PROCEDURE


Iac = VR2 /R2 = mApk-pk

Recall Label for this Question: Iacc

Nominal Answer: 4.5







VC3 = Vpk-pk

Recall Label for this Question: Vc3

Nominal Answer: 7.2







VC3

ZC3 = ——— = Ω Iac

Recall Label for this Question: Zc3

Nominal Answer: 1600.0 ∗Min/Max Value: (852.9) to ( 3001)

Value Calculation: #Vc3#/(#Iacc#/1000)






value.


3-107


C1 x C2

CT =

C1 + C2

= µF



Min/Max Value: (0.049) to (0.051)






10. Did adding the capacitor in series increase or decrease CT?

a. increase

b. decrease


Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: Iaccc

Nominal Answer: 2.8







VCT = Vpk-pk

Recall Label for this Question: Vct

Nominal Answer: 8.9







3-108


14. Compare your data from the two circuits. Which circuit offers the greatest opposition to

current flow (impedance) for the same input signal (VGEN)?

a. single-capacitor circuit

b. two-capacitor series circuit


17. Determine CT in the two-capacitor parallel circuit.

CT = C3 + C4

= µF


Nominal Answer: 0.2







18. Determine Iac by using current-sensing resistor R2.

Iac = VR2 /R2

= mApk-pk


Nominal Answer: 5.8







3-109


19. Measure the voltage drop across parallel capacitors C3 and C4 (VC).

VC = Vpk-pk

Recall Label for this Question: Vc

Nominal Answer: 4.6







21. Compare your data from the two circuits. Which circuit offers the greatest impedance for the

same input signal?

a. single-capacitor circuit

b. two-capacitor parallel circuit


24. Based on the change in circuit current, was the new capacitor added to the circuit in series or

in parallel with C3 or C4?

a. series

b. parallel

REVIEW QUESTIONS


1. The total capacitance of capacitors in series is


b. the sum of the individual capacitor values.

c. the sum of the individual capacitor values divided by two.

d. the reciprocal of the sum of the capacitors.


2. The total capacitance of capacitors in parallel is


b. the sum of the individual capacitor values.

c. the sum of the individual capacitor values divided by two.

d. the reciprocal of the sum of the capacitors.


3-110


3. As more capacitors are added in parallel,

a. circuit current decreases.

b. impedance increases.

c. capacitance decreases.

d. circuit current increases.


4. As more capacitors are added in series,

a. circuit current decreases.

b. impedance decreases.

c. circuit current increases.

d. capacitance increases.


5. Based on the reaction of the circuit current, the unseen capacitor

a. was added in parallel.

b. had no effect on the circuit current.

c. was added in series.

d. caused the circuit current to increase.

CMS AVAILABLE

CM 10 TOGGLE

CM 9 TOGGLE

FAULTS AVAILABLE

None


3-111

UNIT TEST



The total capacitance of two capacitors in series is

a. determined using Ohm's law.

b. always less than the smallest individual capacitor value.

c. the sum of the individual capacitor values.

d. the sum of the individual capacitor values divided by two.


Capacitance is the ability to

a. produce a cemf.

b. induce voltage.

c. hold electric charge.

d. produce a magnetic field.


A capacitor allows dc current to flow only when it is

a. charging or discharging.

b. charging.

c. discharging.

d. fully charged.


Two capacitors in series, one 2 µF and one 1 µF, have a combined capacitance of

a. 3.0 µF.

b. 1.5 µF.

c. 2.0 µF.

d. 0.66 µF.


Two capacitors in parallel, one 1 µF and one 3 µF, have a combined capacitance of

a. 3.0 µF.

b. 4.0 µF.

c. 2.0 µF.

d. 0.75 µF.


3-112


Increasing the number of capacitors in series

a. decreases impedance.



d. increases total capacitance.


Increasing the frequency of the signal applied to a capacitor

a. has no effect.



d. increases circuit current.


Increasing the number of capacitors in parallel

a. decreases circuit current.

b. increases impedance.


d. decreases total capacitance.


A capacitor will

a. pass only ac.

b. block dc and ac.

c. pass only dc.

d. block ac.


The phase difference between the applied voltage and current is

a. 45º.

b. 360º.

c. 90º.

d. 180º.

AC1 Fundamentals Unit 7 – Capacitive Reactance

3-113

UNIT 7 – CAPACITIVE REACTANCE

UNIT OBJECTIVE

Determine the characteristics of resistive-capacitive (RC) circuits by using an oscilloscope and

given information.

UNIT FUNDAMENTALS

Location: Unit Fundamentals Page: sf1, Question ID: f1a

If the frequency of the power source (Vac) increases from 1 kHz to 10 kHz, the capacitive

reactance (XC)

a. increases.

b. decreases.


CMS AVAILABLE

None

FAULTS AVAILABLE

None

NEW TERMS AND WORDS

capacitive reactance - the opposition to current flow due to capacitance.

EQUIPMENT REQUIRED






3-114

Exercise 1 – Capacitive Reactance

EXERCISE OBJECTIVE

Determine capacitive reactance (XC) by using calculated and measured values. Verify results

with an oscilloscope.

EXERCISE DISCUSSION

Location: Exercise Discussion Page: se1d3, Question ID: e1d3a

If C1 is increased from 0.1 µF to 0.8 µF, capacitive reactance

a. increases.

b. decreases.


Location: Exercise Discussion Page: se1d3, Question ID: e1d3c

When a sine wave of 1 kHz is applied to a capacitor of 0.2 µF, what is capacitive reactance?

a. 5000Ω.

b. 1.25 x 10-3Ω.

c. 796Ω.

EXERCISE PROCEDURE

Location: Exercise Procedure Page: se1p4, Question ID: e1p4a

Iac = VR2 /R2

= mApk-pk

Recall Label for this Question: Iaca

Nominal Answer: 4.5







3-115

Location: Exercise Procedure Page: se1p4, Question ID: e1p4c

5. Measure VC3 with the oscilloscope.

VC3 = Vpk-pk

Recall Label for this Question: Vc3a

Nominal Answer: 7.2







VC3

XC3 = = Ω

Iac

Recall Label for this Question: Xc

Nominal Answer: 1600 ∗Min/Max Value: (836) to (3061)

Value Calculation: #Vc3a#/(#Iaca#/1000)





1

XC3 = = Ω

2πfC

Recall Label for this Question: Xc1


Min/Max Value: (1574.1) to (1605.9)







value.


3-116


8. Comparing your values of XC3 from the practical method (#Xc#Ω) and the calculated method

(#Xc1#Ω), does it appear that either method can be used?

a. yes

b. no


9. CM 9 is activated to decrease the value of C3 to 0.05 µF. If necessary, readjust VGEN for a 10

Vpk-pk sine wave at 1 kHz. Determine the total circuit current (Iac).

Iac = VR2 /R2 = mApk-pk

Recall Label for this Question: Iacb







10. Measure the voltage drop across C3 (VC3) with the oscilloscope.

VC3 = Vpk-pk

Recall Label for this Question: Vc3L

Nominal Answer: 8.9







12. Compare your values of capacitive reactance with C3 equal to 0.1 µF (#Xc#Ω) and 0.05 µF

(# ( Vc3L / ( Iacb / 1000 ) )#Ω). Does decreasing capacitance increase or decrease capacitive

reactance?

a. increase

b. decrease



value.


3-117


VC3

XC3 = = Ω

Iac









14. Compare your values of capacitive reactance at 1 kHz (#Xc#Ω) and 500 Hz (#Xc2#Ω). Does

decreasing the frequency of the applied signal increase or decrease capacitive reactance?

a. increase

b. decrease


VC3

XC3 = = Ω

Iac


Nominal Answer: 1600 ∗Min/Max Value: (669) to (3673)

Value Calculation: #Xc#






value.


3-118


16. Compare your values of capacitive reactance at a generator input of 10 Vpk-pk (#Xc#Ω) and

at 8 Vpk-pk (#Xc3#Ω). Decreasing amplitude of the applied signal causes capacitive reactance to

a. increase.

b. decrease.

c. remain the same.

REVIEW QUESTIONS

Location: Review Questions Page: se1r1, Question ID: e1r1a

VC3

XC3 = = Ω

Iac

Recall Label for this Question: XC4







Location: Review Questions Page: se1r1, Question ID: e1r1c

VC3

XC3 = ——— = Ω

Iac

Recall Label for this Question: XC5


Min/Max Value: (556.5) to (1033.5)






3-119

Location: Review Questions Page: se1r1, Question ID: e1r1

1. Compare your value of capacitive reactance before CM 10 was activated (#XC4#Ω) with the

value after CM 10 was activated (#XC5#Ω). You conclude that CM 10

a. decreased the capacitance.

b. increased the amplitude of VGEN.

c. increased capacitance.

d. increased XC3.


2. A 750 Hz, 12 Vpk-pk sine wave applied to a capacitor measuring 0.3 µF has a capacitive

reactance (XC) of

a. 708Ω.

b. 1.41Ω.

c. 59Ω.

d. 7.8 kΩ.


3. Increasing the amplitude of the signal applied to a capacitor

a. decreases capacitive reactance.

b. has no effect on capacitive reactance.

c. increases capacitive reactance.



4. Capacitive reactance decreases when

a. frequency increases.

b. capacitance decreases.

c. frequency decreases.

d. amplitude increases.


5. The equation used to determine capacitive reactance in this exercise is valid for

a. sine waves and square waves.


c. sine waves only.

d. all ac waveforms.


3-120

CMS AVAILABLE

CM 9

CM 10

FAULTS AVAILABLE

None


3-121

Exercise 2 – Series RC Circuits

EXERCISE OBJECTIVE

Determine characteristics of series RC circuits by using calculated and measured values. Verify


EXERCISE DISCUSSION


The total value of resistance (RT) in the series RC circuit shown is 2750Ω (RT = R1 + R2 + R3).

The total value of capacitive reactance (XCT) is

a. 666Ω.

b. 3000Ω.

c. 1000Ω.

Location: Exercise Discussion Page: se2d4, Question ID: e2d4c

Using the values of RT and XCT, calculate the impedance of this series RC circuit.

___________

Z = √ RT2 + XCT

2

= Ω



Min/Max Value: (5102.5) to (5205.5)






3-122


______________

Vac = √VRT2 + VXCT

2

= V



Min/Max Value: (11.18) to (11.41)






θ = degrees



Min/Max Value: (36.96) to (68.64)





EXERCISE PROCEDURE



Recall Label for this Question: IT10

Nominal Answer: 4.5







3-123


VGEN

Z = = Ω

IT

Recall Label for this Question: Z10


Min/Max Value: (1555.4) to (2888.6)






8. Compare your value of Z with the individual values of RT and CT. Can Z be determined by

directly adding RT and CT?

a. yes

b. no


VC3 = Vpk-pk

Recall Label for this Question: Vc3d

Nominal Answer: 7.3







10. Connect the oscilloscope as shown and use the ADD-INVERT method to measure the

voltage drop across R1 (VR1).

VR1 = Vpk-pk

Recall Label for this Question: Vr1d

Nominal Answer: 6.9







3-124


12. Compare your value of VGEN (#( ( ( Vr1d ^ 2) + ( Vc3d ^ 2 ) ) ^ 0.5 ) # Vpk-pk) with the

individual voltage drops of VR1 (#Vr1d# Vpk-pk) and VC1 (#Vc3d# Vpk-pk). In a series RC

circuit, does the applied voltage (VGEN) equal the sum of the individual component drops?

a. yes

b. no


13. Observe the phase angle (θ) between the circuit current (circuit current and VR2 have

identical phase) and VGEN. Use VGEN as a reference. Does the circuit current lead or lag the

applied generator voltage?

a. lead

b. lag


16. Did the added series capacitor increase or decrease the phase angle between VGEN and the

circuit current?

a. decrease

b. increase

REVIEW QUESTIONS


1. While observing the oscilloscope, toggle the CM off and on by clicking on <CM>. Based on

your observation of the circuit current, you conclude that adding a series capacitor to this circuit

a. increased circuit current.

b. decreased circuit impedance.

c. had no effect on circuit current.

d. decreased circuit current.


2. An RC circuit containing three series-connected capacitors with reactances of 200Ω, 500Ω,

and 1500Ω has a total capacitive reactance of

a. 131Ω.

b. 2.5 kΩ.

c. 2.2 kΩ.

d. 150Ω.


3-125


3. In a series RC circuit, the applied generator voltage equals the

a. square root of the sum of the squares of the individual voltage drops across the

individual resistors and capacitors.

b. sum of the voltage drops across the individual resistive components.

c. square root of the sum of the squares of the individual voltage drops across the capacitors.

d. sum of the voltage drops across the individual resistors and capacitors.


4. The total capacitive reactance of capacitors in series is



c. the sum of the individual capacitances.

d. the reciprocal of the individual capacitances.


5. The phase angle between the applied generator and circuit current in a series RC circuit is

a. 90º.

b. 180º.

c. greater than 90º.

d. less than 90º.

CMS AVAILABLE

CM 9 TOGGLE

FAULTS AVAILABLE

None


3-126

Exercise 3 – Parallel RC Circuits

EXERCISE OBJECTIVE

Determine characteristics of parallel RC circuits by using calculated and measured values. Verify


EXERCISE DISCUSSION


XC1 x XC2

XCT = —————— = Ω

XC1 + XC2

Recall Label for this Question: XCTP


Min/Max Value: (742.5) to (757.5)






Calculate total circuit current (IT).

________

IT = √IR2 + IC

2 = mApk-pk



Min/Max Value: (23.76) to (24.24)






3-127

EXERCISE PROCEDURE


IT = VR2 /R2

= mApk-pk

Recall Label for this Question: ITpar

Nominal Answer: 9.1







Does IT equal the sum of the individual branch currents in a parallel RC circuit?

a. yes

b. no


Does the added parallel capacitor cause total capacitive reactance (XCT) to increase or to

decrease?

a. increase

b. decrease


8. Determine the new total circuit current (IT) by using sensing resistor R2.


Recall Label for this Question: ITpar1








3-128


10. Compare your value of circuit impedance with one capacitor (#10/(ITpar/1000) #Ω ). to the

value of circuit impedance with two capacitors (#10/(ITpar1/1000)#Ω). Did the added parallel

capacitor cause the circuit impedance to increase or decrease?

a. increase

b. decrease

REVIEW QUESTIONS


1. Based on your observation of the circuit current, you conclude that adding a parallel capacitor

to the RC circuit

a. decreased circuit current.

b. increased circuit impedance.

c. decreased circuit impedance.

d. had no effect on the circuit.


2. An RC circuit consisting of two parallel-connected capacitors with reactances of 750Ω and 75

kΩ has a total capacitive reactance of

a. 75.75 kΩ.

b. 743Ω.

c. 770Ω.

d. 75 kΩ.


3. The circuit current of a parallel RC circuit equals the square root of the sum of the

a. squares of the resistive and capacitive branch voltages.

b. resistive and capacitive branch voltages.

c. squares of the resistive and capacitive branch currents.

d. resistive and capacitive branch currents.


4. The total capacitive reactance of capacitors in parallel is

a. the sum of the individual capacitances.


c. determined from the reciprocal formula.

d. the reciprocal of the individual capacitances.


3-129


5. As capacitors are added in parallel,

a. phase angle increases.


c. circuit impedance increases.

d. capacitive reactance increases.

CMS AVAILABLE

CM 10 TOGGLE

FAULTS AVAILABLE

None


3-130

UNIT TEST


Location: Unit Test Page: sut1, Question ID: ut1

Capacitive reactance depends on

a. amplitude and frequency.

b. capacitance and amplitude.

c. frequency and capacitance.

d. capacitance only.


Capacitive reactance

a. lies on the positive portion of the Y axis of the X-Y coordinate system.

b. equals 1/(2pfC).

c. is added to resistance to yield total circuit impedance.

d. is multiplied by resistance to yield total circuit impedance.


What capacitive reactance results when a 7 Vpk-pk, 20 kHz sine wave is applied to a capacitor of

12 pF [XC = 1/(2πfC)]?

a. 94.8 kΩ b. 595 kΩ c. 663 kΩ

d. 4.17 MΩ


Adding capacitors in series to an RC circuit a. decreases capacitive reactance.

b. increases phase angle.


d. decreases circuit impedance.


Adding capacitors in parallel to an RC circuit

a. increases capacitive reactance.


c. increases circuit impedance.



3-131


The equation XC = 1/(2πfC) is valid for

a. all ac waveforms.



d. sine waves only.


As capacitors are added in series,

a. circuit impedance decreases.


c. capacitive reactance increases.

d. capacitive reactance decreases.


The current flowing through a capacitor

a. lags the voltage across the capacitor by 90º.

b. is in phase with the voltage across the capacitor.

c. leads the voltage across the capacitor by 90º.

d. lags the voltage across the capacitor by 45º.


When capacitors are added in parallel,

a. capacitive reactance decreases.


c. capacitive reactance increases.

d. circuit impedance increases.


Increasing the frequency of the signal applied to a capacitor

a. increases capacitive reactance.

b. has no effect on capacitive reactance.

c. decreases capacitive reactance.

d. increases the voltage drop across the capacitor.


3-132

TROUBLESHOOTING


3. To ensure proper circuit operation (performance check), measure the output voltage across C2

(VC2) as a result of the input voltage (VGEN).

VC2 = Vpk-pk


Nominal Answer: 4.5








a. C2 (shorted).

b. C1 (increased in value).

c. R1 (shorted).

d. C2 (open).


3. To ensure proper circuit operation (performance check), measure the output voltage across C2

(VC2) as a result of the input voltage (VGEN).

VC2 = Vpk-pk


Nominal Answer: 4.5







3-133



a. C2 (shorted).

b. C1 (increased in value).

c. R1 (shorted).

d. C2 (open).




VR3 = Vpk-pk


Nominal Answer: 1.0

Min/Max Value: (.7) to (1.3)







a. C4 (increased in value).

b. C4 (open).

c. R1 (decreased in value).


CMS AVAILABLE

None

FAULTS AVAILABLE

Fault 9

Fault 10

Fault 11


3-134

AC1 Fundamentals Unit 8 – AC1 Fundamentals

3-135

UNIT 8 – TIME CONSTANTS

UNIT OBJECTIVE

Describe the effects of time constants on ac and dc circuits by using calculated and measured

values.

UNIT FUNDAMENTALS


The sixth harmonic frequency of a 100 Hz square wave is a. 400 Hz.

b. 100 Hz.

c. 600 Hz.

Location: Unit Fundamentals page: sf2, Question ID: f2c

Harmonic frequencies that are first, third, fifth, etc. multiples of the fundamental frequency are

a. even harmonics.

b. odd harmonics.

c. fundamental harmonics.

CMS AVAILABLE

None

FAULTS AVAILABLE

None


3-136

NEW TERMS AND WORDS

fundamental frequency - the principal component of a wave; the component with the lowest

frequency or greatest amplitude. For example, the fundamental frequency of a 100 Hz square

wave is 100 Hz.

harmonic frequencies - sinusoidal waves having frequencies that are integral (positive whole

number) multiples of the fundamental frequency. For example, a wave with twice the frequency

of the fundamental is called the second harmonic.

even harmonics - harmonic frequencies that are even multiples of the fundamental frequency.

For example, 200 Hz and 400 Hz waves are even harmonics of a 100 Hz wave.

odd harmonics - harmonic frequencies that are odd multiples of the fundamental frequency. For

example, 300 Hz and 500 Hz waves are odd harmonics of a 100 Hz wave.

time constant - time required for voltage or current to rise or fall by 63 percent. It results from

the ability of inductance (L) and capacitance (C) to store energy.

EQUIPMENT REQUIRED



Multimeter




3-137

Exercise 1 – RC Time Constants

EXERCISE OBJECTIVE

Determine the time constant of an RC circuit by using calculated and measured values. Verify


EXERCISE DISCUSSION


τ = ms








Location: Exercise Discussion page: se1d3, Question ID: e1d3c

In this example, the time required for the capacitor to fully charge (or discharge) is

a. 250 ms.

b. 50 ms.

c. 99 ms.


The voltage across the capacitor (C1) should be what percent of the original value (10 Vdc) after

three time constants?

= percent


Nominal Answer: 5.0







3-138

EXERCISE PROCEDURE


2. Locate the RC TIME CONSTANTS circuit block, and connect the circuit shown. While

monitoring the voltage across R1 (VR1) with an oscilloscope, press and hold (close) S1. Based

on your observation, did the voltage across R1 develop instantaneously or was there a time

constant delay?

a. delayed

b. instantaneous


4. Connect the oscilloscope input across C1. Make sure the probe is set to 10X. Measure the time

required for the capacitor to charge to VA (15 Vdc) by pressing (holding) S1 and using the

second hand of a watch or clock. Begin timing at the instant you close S1.

Charge time = seconds

Recall Label for this Question: tc

Nominal Answer: 5.0







6. Compare your measured value of total charging time (#tc# seconds) to the calculated value of

one time constant. Was the total time required to charge C1 to 15 volts approximately equal to

five time constants?

a. yes

b. no


τ = seconds


Nominal Answer: 2.0







3-139


8. Use the universal time constant chart to determine the percentage of voltage across C1 and C2

(VC) after VA is applied for two time constants.

Voltage = percent



Min/Max Value: (84.28) to (87.72)






9. Make sure the capacitors are discharged by pressing S2 (zero volts across C1 and C2). Make

sure your probe is set to 10X. Determine VC after 2 time constants (4 seconds) have expired by

pressing S1, releasing it after 4 seconds, and immediately taking the measurement.

VC after 4 seconds = volts

Recall Label for this Question: vc85


Min/Max Value: (8.385) to (17.42)






10. Compare your measured voltage of VC (#vc85#) with the percentage of applied voltage

across C1 and C2 by using the universal time constant chart. Can you accurately predict the

voltage across a capacitor by using the universal time constant chart?

a. yes

b. no


3-140

REVIEW QUESTIONS


1. While observing an oscilloscope connected across C1, press S1 and measure the time required

for the capacitor to charge to 15 Vdc (TC). Start timing at the instant S1 is closed.

TC = seconds

Recall Label for this Question: tc1

Nominal Answer: 5.0







1. Make sure C1 is completely discharged by pressing S2 until you measure zero volts across C1.

CM 3 is activated to reduce the value of C1. Remeasure the time required to charge C1.

TC = seconds

Recall Label for this Question: tc2








1. You conclude that

a. decreasing the capacitance increased the RC time constant.

b. changing the capacitance had no effect on the RC time constant.

c. decreasing the capacitance decreased the RC time constant.

d. the more capacitive the circuit, the shorter the RC time constant.


3-141


2. A circuit with resistance of 75 kΩ and capacitance of 4.7 µF has an RC time constant of

a. 1.59s.

b. 353 ms.

c. 3.53s.

d. 159 ms.


3. Increasing the value of resistance in an RC circuit

a. causes the time constant to increase.

b. has no effect on the time constant.

c. causes the time constant to decrease.

d. increases the dc current flow through the circuit.


4. A capacitor is considered to be fully discharged after

a. one time constant.

b. six time constants.

c. two time constants.

d. five time constants.


5. Use the universal time constant chart to determine

a. charge and discharge times of RC and RL circuits.

b. charge and discharge times of RC circuits only.

c. only charge times of RC and RL circuits.

d. only discharge times of RC and RL circuits.

CMS AVAILABLE

CM 3

FAULTS AVAILABLE

None


3-142

Exercise 2 – RC and RL Wave Shapes

EXERCISE OBJECTIVE

Demonstrate the effects of time constants on RC and RL circuits by using square waves as the

applied ac waveforms. Verify results with a universal time constant chart.

EXERCISE DISCUSSION


With one time constant equal to 2 ms, how long will it take to fully charge the capacitor (C) to

the peak voltage of the square wave input?

a. 2 ms

b. 10 ms

c. 4 ms


If the value of the resistor (R) increased in value, would the time to fully charge the capacitor

increase or decrease?

a. increase

b. decrease


If the value of the inductor (L) decreased in value, would the charge and discharge time of the

inductor increase or decrease?

a. increase

b. decrease


3-143

EXERCISE PROCEDURE


5. If each major division along the horizontal axis equals one time constant, how many time

constants are required for the capacitor to fully charge?

a. 1

b. 3

c. 5


VC1 = V


Nominal Answer: 6.8







VC1 = V


Nominal Answer: 1.1







Connect the oscilloscope across C1, and toggle CM 4 off and on by clicking on <CM>. What

type of waveform results when CM 4 is activated?

a. square wave

b. sawtooth wave

c. sine wave


3-144


12. Judging from the waveforms displayed, would you say current flow is maximum at the

beginning or at the end of the charge and discharge times?

a. beginning

b. end


Using the oscilloscope, measure the voltage level across the inductor (VL1) after it has charged

for 1 time constant (10 µs).

VL1 = V


Nominal Answer: 3.0







19. Do positive voltage spikes across L1 occur on the rising edges or on the falling edges of

VGEN?

a. rising edges

b. falling edges


22. Judging from the displayed waveforms, would you say current flow is maximum at the

beginning of a charging cycle or at the end?

a. beginning

b. end


3-145

REVIEW QUESTIONS


1. Based on your observation of the current waveform, what can you conclude about the circuit?

a. The RC time constant increased.

b. The value of the capacitor increased.

c. Changing the value of C2 had no effect on the current.

d. The value of the capacitor decreased.


2. Decreasing the value of inductance in an RL circuit (τ = L/R)

a. increases the RL time constant.

b. has no effect on the RL time constant.

c. decreases the RL time constant.

d. prevents voltage spikes from occurring when a square wave is applied to the circuit.


3. The current in an RL circuit is

a. minimum at the beginning of charging time.

b. maximum at the beginning of charging time.

c. minimim at the end of discharging time.

d. maximum at the beginning of discharging time.


4. Applied to an RL circuit is a square wave with a period much longer than the RL time

constant. The inductor voltage produces a

a. sine wave.

b. cosine wave.

c. sawtooth wave.

d. voltage spike.


5. The voltage across the capacitor in an RC circuit is

a. maximum at the beginning of charging time.

b. minimum at the end of charging time.

c. minimum at the beginning of charging time.

d. zero at the end of charging time.


3-146

CMS AVAILABLE

CM 4 TOGGLE

CM 7 TOGGLE

CM 6 TOGGLE

FAULTS AVAILABLE

None


3-147

UNIT TEST



One time constant is the amount of time required for current in an inductive circuit or for voltage

in a capacitive circuit to reach approximately what percent of its maximum value?

a. 10

b. 86

c. 63

d. 98


You can determine the time constant of an RC circuit by using the equation

a. R/C.

b. R x C.

c. C/R.

d. 1/RC.


You can determine the time constant of an RL circuit by using the equation

a. R/L.

b. L/R.

c. RL.

d. 1/RL.


A capacitor in an RC circuit is considered to be fully charged after

a. 4 time constants.

b. 1 time constant.

c. 3 time constants.

d. 5 time constants.


A series RC circuit consisting of a 4.7 µF capacitor and a 4.7 kΩ resistor has a time constant

value of

a. 22.1 ms.

b. 45.3s.

c. 221 ms.

d. 4.53s.


3-148


A series RL circuit consisting of a 22 mH inductor and a 3.3 kΩ resistor has a time constant

value of

a. 13.8 ms.

b. 6.67 µs.

c. 667 µs.

d. 1.38 ms.


In an RC circuit having a time constant of 3 ms, the capacitor will fully charge (assuming there is

no initial charge) in

a. 9 ms.

b. 3 ms.

c. 6 ms.

d. 15 ms.


The circuit current in an RC circuit is

a. maximum at the beginning of charging time.

b. minimum at the beginning of charging time.

c. maximum at the end of charging time.

d. minimum at the beginning of discharging time.


An RC circuit has an applied square wave with a period that is too short to allow the capacitor to

fully charge and discharge. The capacitor voltage produces a

a. square wave.

b. sine wave.

c. sawtooth wave.

d. cosine wave.


The second harmonic of a 200 Hz square wave is

a. 200 Hz.

b. 600 Hz.

c. 800 Hz.

d. 400 Hz.


3-149

TROUBLESHOOTING


2. To ensure proper circuit operation (performance check), measure the time required for the

capacitors to charge to VA (15 Vdc) by pressing (holding) switch S1. Use the second hand of a

watch or clock to begin timing at the instant S1 is closed.

Charge time (t) = s










a. C1 (shorted).

b. R2 (decreased in value).

c. R2 (open).

d. C1 (open).



capacitors to charge to VA (15 Vdc) by pressing (holding) switch S1. Use the second hand of a

watch or clock to begin timing at the instant S1 is closed.

Charge time (t) = s









3-150



a. C1 (shorted).

b. R2 (decreased in value).

c. R2 (open).

d. C1 (open).


3. To ensure proper circuit operation (performance check), measure the time required for C1 to

charge to VGEN (8V).

Charge time = ms


Nominal Answer: 5.0








a. R1 (increased in value).

b. C1 (shorted).

c. R1 (shorted).

d. C1 (increased in value).

Location: Troubleshooting page: ttrbd2, Question ID: trbd2a


voltage across R2 (representing circuit current) to go to zero.

time = ms


Nominal Answer: 5.0







3-151

Location: Troubleshooting page: ttrbd3, Question ID: trbd3


a. C2 (decreased in value).

b. R2 (shorted).

c. C2 (shorted).


Location: Troubleshooting page: ttrbe2, Question ID: trbe2a


voltage across R4 (representing circuit current) to go to maximum.

time = µs








Location: Troubleshooting page: ttrbe3, Question ID: trbe3


a. R4 (open).

b. L2 (decreased in value).

c. R4 (decreased in value).

d. L2 (shorted).

CMS AVAILABLE

None

FAULTS AVAILABLE

Fault 1

Fault 2

Fault 3

Fault 6

Fault 12


3-152

AC1 Fundamentals Appendix A – Pretest and Posttest Questions and Answers

A-1

APPENDIX A – PRETEST AND POSTTEST QUESTIONS AND ANSWERS


Pretest Questions

1. One complete repetition of an ac waveform is

a. the amplitude.

b. the frequency.

c. a cycle.

d. the polarity.

2. Which oscilloscope control setting is used to measure time?

a. trigger mode

b. hold off

c. level

d. time base

3. To view two waveforms on a dual trace oscilloscope simultaneously, you must set the

vertical mode to

a. ADD.

b. CHOP.

c. ALT.

d. either CHOP or ALT.

4. AC voltage and current differ from dc voltage and current because ac voltage and current

a. are not really electricity.

b. never change.

c. change polarity.

d. maintain a constant polarity.

5. When a X10 probe is in use, an oscilloscope screen displays an ac waveform that is ten times

a. smaller.

b. larger.

c. slower.

d. faster.

6. An oscilloscope can directly measure ac

a. and dc voltage.

b. voltage only.

c. and dc voltage and current.

d. voltage and current.


A-2

7. The oscilloscope screen is divided by a gridwork of horizontal and vertical scale lines called

the

a. graduate.

b. time base.

c. graticule.

d. grate.

8. The maximum amplitude of an ac waveform in either polarity is the


b. effective amplitude.

c. peak amplitude.

d. average amplitude.

9. Which value of an ac waveform delivers the same amount of power as the dc waveform of

the same amplitude?

a. absolute value

b. rms value

c. average value

d. peak value

10. The reciprocal of the frequency of an ac waveform equals the

a. phase angle.

b. peak value.

c. current.

d. period.

11. When phase angle is measured by an oscilloscope, the reference waveform should

a. not be used as the trigger source.

b. be a square wave.

c. be used as the trigger source.

d. not be a sine wave.

12. When phase angle is measured by an oscilloscope, a lagging waveform is

a. shifted toward the left of the reference waveform.

b. smaller in amplitude than the reference waveform.

c. shifted toward the right of the reference waveform.

d. larger in amplitude than the reference waveform.

13. How many degrees are in one half of one cycle of a sine wave?

a. 90°

b. 180°

c. 360°

d. 200°


A-3

14. When the magnetic field surrounding a conductor fluctuates due to changing current flow,

a. counter electromotive force is produced.

b. additional current is produced.

c. electromotive force is produced.

d. the conductor emits light.

15. Inductance is measured in

a. henries.

b. ohms.

c. hertz.

d. angstroms.

16. Winding a conductor into a coil

a. cancels out eddy currents.

b. concentrates the magnetic field.

c. reduces inductance.

d. cancels out the magnetic field.

17. The voltage across an inductor

a. leads the current by 45°.

b. leads the current by 90°.

c. lags the current by 90°.

d. lags the current by 45°.

18. When inductors are connected in parallel

a. current flow decreases.

b. total inductance increases.

c. impedance increases.

d. total inductance decreases.

19. When inductors are connected in series,

a. current flow increases.

b. inductive reactance decreases.

c. impedance decreases.


20. When the frequency of the signal applied to an RL circuit increases,

a. impedance decreases.

b. inductive reactance increases.

c. current flow increases.



A-4

21. A phasor

a. has magnitude only.

b. is a phase angle.

c. has magnitude and direction.

d. is measured in cycles per second.

22. Inductive reactance lies on which axis of the X-Y coordinate plane?

a. negative Y

b. negative X

c. positive Y

d. positive X

23. An increase in the measure of inductance


b. increases current flow.



24. Total impedance of an RL circuit is determined from the equation

__________

a. √ R2

+ XL2

.

b. R + L.

c. RL.

d. R2

+ XL2

.

25. An increase in the amplitude of the signal applied to an inductor


b. increases inductive reactance.


d. does not affect inductive reactance.

26. The reciprocal value of a waveform's period is its

a. phase angle.

b. amplitude.

c. frequency.

d. peak value.

27. The peak value multiplied by 0.707 yields the rms value of

a. sine waves only.



d. any ac waveform.


A-5

28. Two 6 mH inductors in series have a combined inductance of

a. 3 mH.

b. 0.33 mH.

c. 12 mH.

d. 24 mH.

29. You can determine the total inductance of several inductors in series by

a. adding the individual inductances.

b. the product-over-sum method.

c. the reciprocal method.

d. multiplying the individual inductances.

30. The equation XL = 2πfL is valid for

a. all ac waveforms..


c. sine waves and square waves..

d. sine waves only.

31. A transformer works on the principle of

a. self-inductance.

b. mutual conduction.

c. mutual inductance.

d. self-conduction.

32. In a transformer, a voltage appears across the secondary windings only when the voltage

across the primary is

a. changing.

b. dc voltage.

c. ac voltage.

d. unchanging.

33. In a step-down transformer, the voltage on the primary is

a. equal to the voltage on the secondary.

b. zero.

c. greater than the voltage on the secondary.

d. less than the voltage on the secondary.

34. The transfer of energy from one circuit to another is

a. the conduction angle.

b. coupling.

c. decoupling.

d. inductance.


A-6

35. The turns ratio of a transformer equals the

a. current ratio.

b. power ratio.

c. voltage-to-current ratio.

d. voltage ratio.

36. Capacitance is the ability to

a. induce voltage.

b. produce a magnetic field.

c. produce an electric field.

d. hold electric charge.

37. Which type of capacitor uses a molecularly thin metal oxide to produce relatively high values

of capacitance in a very small space?

a. electrolytic

b. mylar

c. ceramic

d. mica

38. The voltage across the capacitor

a. lags the current by 45°.

b. lags the current by 90°.

c. leads the current by 90°.

d. leads the current by 45°.

39. When capacitors are connected in parallel,


b. total capacitance decreases.


d. total capacitance increases.

40. A charged capacitor

a. blocks dc current and passes ac current.

b. blocks ac current and passes dc current.

c. blocks both ac and dc current.

d. passes both ac and dc current.

41. When capacitors are connected in series,


b. capacitive reactance increases.




A-7

42. When the capacitance of an RC circuit increases,





43. When the frequency of the signal applied to an RC circuit decreases,


b. capacitive reactance decreases.



44. Capacitive reactance lies on which axis of the X-Y coordinate plane?

a. negative X

b. negative Y

c. positive X

d. positive Y

45. An increase in the amplitude of the signal applied to a capacitor


b. increases capacitive reactance.


d. does not affect capacitive reactance.

46. A capacitor is considered to be fully charged after how many time constants?

a. 3

b. 4

c. 5

d. 6

47. The first harmonic frequency of a 100 Hz square wave is

a. 200 Hz.

b. 10 Hz.

c. 100 Hz.

d. 1000 Hz

48. When dc is applied to an initially uncharged RL circuit, current flow is

a. minimum at the end of charging time.



d. maximum at the end of charging time.


A-8

49. When dc is applied to an initially uncharged RC circuit, current flow is


b. maximum at the end of charging time.

c. maximum at the beginning of charging time.

d. minimum at the beginning of discharge time.

50. The time constant (τ) of an RL circuit is determined from the equation

a. R x L.

b. L/R.

c. R/L.

d. 1/(R x L).


A-9

Posttest Questions

1. Which value of an ac waveform delivers the same amount of power as the dc waveform of

the same amplitude?

a. absolute value

b. rms value

c. average value

d. peak value

2. How many degrees are in one half of one cycle of a sine wave?

a. 90°

b. 180°

c. 360°

d. 200°

3. The oscilloscope screen is divided by a gridwork of horizontal and vertical scale lines called

the

a. graduate.

b. time base.

c. graticule.

d. grate.

4. The voltage across an inductor

a. leads the current by 45°.

b. leads the current by 90°.

c. lags the current by 90°.

d. lags the current by 45°.

5. When the magnetic field surrounding a conductor fluctuates due to changing current flow,

a. counter electromotive force is produced.

b. additional current is produced.

c. electromotive force is produced.

d. the conductor emits light.

6. When phase angle is measured by an oscilloscope, the reference waveform should

a. not be used as the trigger source.

b. be a square wave.

c. be used as the trigger source.

d. not be a sine wave.


A-10

7. When a X10 probe is in use, an oscilloscope screen displays an ac waveform that is ten times

a. smaller.

b. larger.

c. slower.

d. faster.

8. When phase angle is measured by an oscilloscope, a lagging waveform is

a. shifted toward the left of the reference waveform.

b. smaller in amplitude than the reference waveform.

c. shifted toward the right of the reference waveform.

d. larger in amplitude than the reference waveform.

9. An oscilloscope can directly measure ac

a. and dc voltage.

b. voltage only.

c. and dc voltage and current.

d. voltage and current.

10. When inductors are connected in series,


b. inductive reactance decreases.



11. The reciprocal of the frequency of an ac waveform equals the

a. phase angle.

b. peak value.

c. current.

d. period.

12. AC voltage and current differ from dc voltage and current because ac voltage and current

a. are not really electricity.

b. never change.

c. change polarity.

d. maintain a constant polarity.

13. When inductors are connected in parallel


b. total inductance increases.


d. total inductance decreases.


A-11

14. Inductance is measured in

a. henries.

b. ohms.

c. hertz.

d. angstroms.

15. The maximum amplitude of an ac waveform in either polarity is the


b. effective amplitude.

c. peak amplitude.

d. average amplitude.

16. One complete repetition of an ac waveform is

a. the amplitude.

b. the frequency.

c. a cycle.

d. the polarity.

17. When the frequency of the signal applied to an RL circuit increases,

a. impedance decreases.

b. inductive reactance increases.

c. current flow increases.


18. The reciprocal value of a waveform's period is its

a. phase angle.

b. amplitude.

c. frequency.

d. peak value.

19. A phasor

a. has magnitude only.

b. is a phase angle.

c. has magnitude and direction.

d. is measured in cycles per second.

20. Which oscilloscope control setting is used to measure time?

a. trigger mode

b. hold off

c. level

d. time base


A-12

21. Winding a conductor into a coil

a. cancels out eddy currents.

b. concentrates the magnetic field.

c. reduces inductance.

d. cancels out the magnetic field.

22. Total impedance of an RL circuit is determined from the equation

a. √ R2 + XL

2.

b. R + L.

c. RL.

d. R2

+ XL2

.

23. To view two waveforms on a dual trace oscilloscope simultaneously, you must set the

vertical mode to

a. ADD.

b. CHOP.

c. ALT.

d. either CHOP or ALT.

24. The equation XL = 2πfL is valid for

a. all ac waveforms..


c. sine waves and square waves..

d. sine waves only.

25. An increase in the amplitude of the signal applied to an inductor


b. increases inductive reactance.


d. does not affect inductive reactance.

26. Capacitance is the ability to

a. induce voltage.

b. produce a magnetic field.

c. produce an electric field.

d. hold electric charge.

27. A transformer works on the principle of

a. self-inductance.

b. mutual conduction.

c. mutual inductance.

d. self-conduction.


A-13

28. Two 6 mH inductors in series have a combined inductance of

a. 3 mH.

b. 0.33 mH.

c. 12 mH.

d. 24 mH.

29. Inductive reactance lies on which axis of the X-Y coordinate plane?

a. negative Y

b. negative X

c. positive Y

d. positive X

30. In a transformer, a voltage appears across the secondary windings only when the voltage

across the primary is

a. changing.

b. dc voltage.

c. ac voltage.

d. unchanging.

31. An increase in the measure of inductance


b. increases current flow.



32. The voltage across the capacitor

a. lags the current by 45°.

b. lags the current by 90°.

c. leads the current by 90°.

d. leads the current by 45°.

33. The turns ratio of a transformer equals the

a. current ratio.

b. power ratio.

c. voltage-to-current ratio.

d. voltage ratio.

34. The peak value multiplied by 0.707 yields the rms value of

a. sine waves only.



d. any ac waveform.


A-14

35. When capacitors are connected in series,





36. A capacitor is considered to be fully charged after how many time constants?

a. 3

b. 4

c. 5

d. 6

37. Capacitive reactance lies on which axis of the X-Y coordinate plane?

a. negative X

b. negative Y

c. positive X

d. positive Y

38. In a step-down transformer, the voltage on the primary is

a. equal to the voltage on the secondary.

b. zero.

c. greater than the voltage on the secondary.

d. less than the voltage on the secondary.

39. A charged capacitor

a. blocks dc current and passes ac current.

b. blocks ac current and passes dc current.

c. blocks both ac and dc current.

d. passes both ac and dc current.

40. The first harmonic frequency of a 100 Hz square wave is

a. 200 Hz.

b. 10 Hz.

c. 100 Hz.

d. 1000 Hz

41. When capacitors are connected in parallel,


b. total capacitance decreases.


d. total capacitance increases.


A-15

42. You can determine the total inductance of several inductors in series by

a. adding the individual inductances.

b. the product-over-sum method.

c. the reciprocal method.

d. multiplying the individual inductances.

43. The transfer of energy from one circuit to another is

a. the conduction angle.

b. coupling.

c. decoupling.

d. inductance.

44. When the frequency of the signal applied to an RC circuit decreases,


b. capacitive reactance decreases.



45. When dc is applied to an initially uncharged RC circuit, current flow is


b. maximum at the end of charging time.

c. maximum at the beginning of charging time.

d. minimum at the beginning of discharge time.

46. Which type of capacitor uses a molecularly thin metal oxide to produce relatively high values

of capacitance in a very small space?

a. electrolytic

b. mylar

c. ceramic

d. mica

47. When the capacitance of an RC circuit increases,





48. The time constant (τ) of an RL circuit is determined from the equation

a. R x L.

b. L/R.

c. R/L.

d. 1/(R x L).


A-16

49. When dc is applied to an initially uncharged RL circuit, current flow is

a. minimum at the end of charging time.



d. maximum at the end of charging time.

50. An increase in the amplitude of the signal applied to a capacitor


b. increases capacitive reactance.


d. does not affect capacitive reactance.

AC1 Fundamentals Appendix B – Faults and Circuit Modifications (CMs)

B-1

APPENDIX B – FAULTS AND CIRCUIT MODIFICATIONS (CMS)

CM SCHEMATIC

SWITCH NO.

FAULT ACTION

– 21 1 opens C1

– 22 2 shorts C1

– 23 3 R1 = 0Ω

– 24 4 opens T1 primary

– 25 5 opens T1

secondary

– 26 6 R2 = 0Ω

– 27 7 shorts L2

– 28 8 opens L4

– 32 12 opens R4

3 3 – places 1 µF in

series with 10 µF

C1

4 4 – R1 = 1 MΩ

5 5 – places 470Ω in

parallel with 1 kΩ

R2

6 6 – places 0.001 µF in

series with 0.01 µF

C2

7 7 – places 1 mH in

parallel with 10

mH L1

16 16 – L3 = 14.7 mH

17 17 – places 1 mH in

parallel with

4.7 mH L3

AC1 Fundamentals Appendix B – Faults and Circuit Modifications (CMs)

B-2

AC1 Fundamentals Appendix C – Board and Courseware Troubleshooting

C-1

APPENDIX C – BOARD AND COURSEWARE TROUBLESHOOTING

Circuit Board Problems

The F.A.C.E.T. equipment is carefully designed, manufactured, and tested to assure long,

reliable life. If you suspect a genuine failure in the equipment, the following steps should be

followed to trace a problem.

A. ALWAYS insert the board into a base unit before attempting to use an ohmmeter for

troubleshooting. The schematic diagrams imprinted on the boards are modified by the

absence of base unit switch connections; therefore, ohmmeter checks will produce erroneous

results with disconnected boards. Do not apply power to the base unit when you perform

resistance checks.

B. Information describing fault switch functions is provided in Appendix B in this instructor

guide.

Courseware Problems

The F.A.C.E.T. courseware has been written to meet carefully selected objectives. All exercises

have been tested for accuracy, and information presented in discussions has been reviewed for

technical content. Tolerances have been computed for all procedure and review question answers

to assure that responses are not invalidated by component or instrument errors.

Nevertheless, you or your students may discover mistakes or experience difficulty in using our

publications. We appreciate your comments and assure you that we will weigh them carefully in

our ongoing product improvement efforts.

As we address courseware problems, we will post corrections for download from our web site,

www.labvolt.com. Select the customer support tab, and then choose product line: F.A.C.E.T.

Select a course, select from a list of symptoms that have been addressed, and follow the

instructions.

AC1 Fundamentals Appendix C – Board and Courseware Troubleshooting

C-2

We will do our best to help you resolve problems if you call the number below. However, for

best results, and to avoid confusion, we prefer that you write with a description of the problem.

If you write, please include the following information:

• Your name, title, mailing address, and telephone number (please include the best time to

reach you).

• Publication title and number.

• Page number(s), and step and/or figure number(s) of affected material.

• Complete description of the problem encountered and any additional information that may

help us solve the problem.

Send your courseware comments to:

[email protected]

Lab-Volt Systems

P.O. Box 686

Farmingdale, NJ 07727

ATTN: Technical Support

If you prefer to telephone regarding hardware or courseware problems, call us between 9:00 AM

and 4:30 PM (Eastern time) at: (800) 522-4436 or (888)-LAB-VOLT.

THIS

THIS

AC 1 Fundamentals

AC 1 Fundamentals

AC 1 Fundamentals

Instructor Guide

Instructor Guide

Instructor Guide

Cut

out

indi

vidu

al b

inde

r sp

ine

labe

ls fr

om th

is p

age

and

inse

rt th

em in

to th

e sp

ine

of th

e ap

prop

riate

gui

des.

Binder Spine Labels

Documents

91562-10 AC1Fundamentals IG ED2 PR1 Web