STEP-UP 2011Lesson Plan: Capacitance

Brian HeglundEtowah High SchoolAdvisor: Phil First

Ultra High Vacuum (UHV) at GT can analyze sample surfaces with Leed and Auger.

Problem: Can this wire be used in the UHV without shorting through the UHV components?

Abstract

Students learn theory of capacitors as summer research experience is related anecdotally. Students apply knowledge to design and construction of two separate circuits with capacitors.

Alignment with GPS

College Board Performance Objectives:

College Board Performance Objectives:● Define the ampere as the unit of electrical current.● Distinguish between conventional flow and electron flow.● State Ohm's Law for electrical components.● Define the unit of resistance, the ohm.● Calculate the resistance across a bank of resistors in series,

parallel, and combined.● Discuss emf and its role in DC electrical theory.● Distinguish between emf and potential difference.● Define and describe voltage, current, and equivalent

resistance for resistors connected in series, parallel, and combined.

College Board Performance Objectives:

● State Ohm's Law for an entire electrical circuit and apply it to the solution of electrical problems involving internal battery resistance and total resistance of the circuit.

● Calculate the total resistance of an entire DC circuit.● Compute power loss in a given DC circuit.● Determine the terminal voltage, given the emf of a battery,

its internal resistance, and the load resistance.● Determine the potential drop across a resistance carrying a

given current.● Define the factors that determine the resistance of a given

wire.● Calculate the resistance of a wire given its resistivity, length,

and radius.

College Board Performance Objectives:

● Relate the potential difference across a resistor carrying a current to its energy loss.

● Define the watt as the unit of electrical power.● Determine the power loss across a given current carrying

resistance.● Write and apply Kirchhoff's Rules for electrical networks in

the determination of unknown currents.● Analyze multiloop circuits using Ohm's Law and Kirchhoff's

Rules.● Calculate the equivalent capacitance of a number of

capacitors arranged in (1) series, (2) parallel, and (3) series and parallel combination.

● Understand how to use ammeters, voltmeters, galvanometers, and the Wheatstone bridge.

College Board Lab Objectives:

● Experimentally, demonstrate Ohm's Law with a voltmeter, an ammeter, a rheostat, a source of emf, and appropriate lead wires and draw a schematic diagram of an electrical set-up, using appropriate symbols for the electrical equipment used.

● Design an experiment to measure the resistivity of a conductor.

● Design an experiment to measure the power loss across a resistance.

● Design and conduct an experiment using two loops, resistors in each loop, and several seats of emf.

● Design and conduct an experiment to find the resistance of unknown resistors using the Wheatstone Bridge.

College Board Lab Objectives:

● Experimentally determine charge and voltage relationships for capacitors in series, parallel, and combined networks.

● Design and conduct an experiment to measure the time constant in an RC circuit.

Anticipated Learner Outcomes

● Demonstrate a comprehension of physical and environmental reality by understanding how fundamental physical principles underlie the huge variety of natural phenomena and their interconnectedness.

● Demonstrate basic experimental skills by the practice of setting up and conducting an experiment with due regards to minimizing measurement error and by the thoughtful discussion and interpretation of data.

● Demonstrate basic communication skills by working in groups on a laboratory experiment.

● http://www.ohlone.edu/instr/physics/courses.html

Rubric

experiment 1: full credit is given if the light bulb illuminatesexperiment 2: full credit is awarded if students successfully experimentally determine breakdown voltage of capacitor.

Background: Wire coating insulates current from traveling through other conductors such as UHV components. When this occurs, a short circuit has

been created.

Background: Two strands of wire were tightly twisted.

Background: At low potential difference, the insulative coating prevents current.

The voltage is less than the coating's breakdown voltage.

Background: Voltage is less than air's breakdown voltage - no current.

Background: When voltage is greater than the wire's voltage, the insulative coating becomes conductive - current flows from one wire to the other, forming a

closed circuit.

Background: Voltage is greater than air's break down voltage - air conducts the current.

Background: First I confirmed that the measuring instruments worked properly.

Background: Next I increased the voltage. If I exceeded the breakdown voltage, a voltage drop would occur across the resistor.

Background

The wire was deemed safe when 1 kilovolt was achieved and no breakdown occurred.

This is one way a capacitor can be modeled.

A capacitor consists of two conductors with an insulative material between them. When a potential difference exists between the conductors, capacitors store energy.

Background

Computer memory chips, or DRAM, use capacitors to store information. Binary code can communicate all letters, numbers and punctuation as ones and zeroes. A potential difference causes charge build up on one of the plates to create this code. A binary "1" or "on" is created when a potential difference exists and charge is stored. A binary "0" or "off" is created when there is no potential difference and no charge is stored.

Supplies

voltage source, wires, resistor, capacitor, light bulb, switch, mulitmeter

Plan: Your assignment is to build a functioning circuit like the one above. The light must illuminate.

Plan: It's your turn to experimentally determine the breakdown voltage of the capacitor. Compare that to the accepted capacitor voltage rating. Let me check

off your configuration before you perform the experiment.

Summary

By hearing my about my summer research at Georgia Tech, students will learn about capacitors and apply knowledge to the design and construction of two circuits with capacitors.