PA GOVERNOR’S INSTITUTE--2005 Ohm’s Law 1

Math-in-CTE Lesson Plan

Lesson Title: Ohm’s Law Lesson Number: 35

Occupational Area: Automotive Technology CTE Concept(s): Ohm’s Law Math Concepts: Solving algebraic equations

Lesson Objective: Students will demonstrate a working knowledge of solving problems involving formulas with specified symbols (math concept) and its application in Automotive Technology: Electrical Systems (technical field), while recognizing it in other contexts.

Supplies Needed: Automotive Technology text, calculator

THE "7 ELEMENTS" TEACHER NOTES (and answer key)

1. Introduce the CTE lesson. Today we’re going to talk about calculating amps, volts and ohms within automotive circuits. When determining wire sizing, fuse sizing, and switch/relay choices, we need to know the demands on each circuit. By calculating our current flow (amps), our electrical pressure (volts), and our resistance to flow (ohms), we can make these determinations.

This lesson follows the introduction of the properties of electricity. Once students become familiar with the concepts of amps, volts, and ohms, they can use this information to calculate missing values using Ohm’s Law.

2. Assess students’ math awareness as it relates to the CTE lesson. Remember the relationship between our electrical measurements (water hose analogy). Ask: 1. What unit of measure is used for each?

It is helpful to compare current characteristics to a water hose with a spray nozzle. As the nozzle is opened (ohms are reduced), the flow of water (current) increases while the pressure (volts) decreases.

Amperage: Amps Voltage: Volts

Resistance: Ohms

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2. How do changes in one relate to changes in the others? Introduce Ohm’s Law:

As Resistance increase: Voltage increases and Amps decrease, etc.

RIE != Voltage = Current x Resistance AND

I

ER =

Resistance = Voltage / Current AND

R

EI =

Current = Voltage / Resistance

3. Work through the math example embedded in the CTE lesson. If I have a circuit with 5 amps and 10 ohms, what is the voltage of the

circuit?

Since RIE != and I=5 and R= 10 then E=(5) x (10) and E = 50 ohms.

4. Work through related, contextual math-in-CTE examples. If you have a circuit with 12 volts and 6 amps, what is the resistance of

the circuit?

If you have a circuit with 24 volts and 10 ohms, what is the current of the circuit?

6

12=R and R=6 ohms

10

24=I and I=2.4 amps

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5. Work through traditional math examples. If you have a rectangle whose length is 14” and width is 5”, what is its area?

What is the speed in m.p.h. of a vehicle that traveled 150 miles in 5 hours?

Area = length x width Area = 14” x 5” Area = 70 sq. in.

Time

DistSpeed =

hours

ilesmSpeed

5

150= Speed = 30 m.p.h.

6. Students demonstrate their understanding. Complete worksheet with 100% accuracy. Students will correct all mistakes until 100% accuracy is achieved.

Students complete a worksheet involving problems of each type, solve for amps, solve for volts, solve for ohms.

7. Formal assessment. Possible Test Questions

1. A 12 volt series circuit contains a 5 ohm resistor. What is the amperage?

2. On a vehicle with a 24-volt system, the starter draws 170 amps.

What is the starter’s resistance?

R

EI =

5

12=I I = 2.4 amps

I

ER =

170

24=R R= .14 ohms

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Adaptations for special needs students. Teacher Notes: Extra time as needed, instructional aid available to read problems if needed

Math Standards and Assessment Anchors addressed with this lesson. M11A.1.1.1, M11A.1.3.1, M11A.2.1.2, M11A.2.1.3, M11A.3.1.1

References. Student text, worksheet

Author(s): Position: School: Kurt Speicher Auto Tech Instructor Crawford County AVTS John Fuller Auto Body Instructor Crawford County AVTS Carol Appleby Math Instructor Dauphin County Technical School Bonnie Campbell Eric McGuirk

Special Ed Instructor Guidance Counselor

Greene County CTC Crawford County AVTS