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Toward Learning and Understanding

Electricity: Challenging Persistent

Misconceptions

Camille L. Wainwright, PhDProfessor of Science

EducationPacific University

wainwric@pacificu.edu

January, 2007

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Challenging Misconceptions

Boston Museum of Science curriculum development: Engineering the Future

Four units – Year-long HS course Unit 4: “Electricity and

Communication” based on CASTLE Electricity curriculum (Capacitor-Aided System for Teaching and

Learning Electricity) Clinical Interviews (qualitative) Pre- and Post-Assessments

(quantitative) Refinement and re-design

following evaluation

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a. Understanding the role of the battery as a source of energy but not a supplier of charge

What is the source of the moving charge in a circuit? “Charges in the circuit I believe

start at the batteries.” (“How do you happen to know

that’s the case?”) “Basically just growing up. The

battery is where the energy is. If you actually put your tongue on a battery it hurts, so I figure that is where the electricity comes from. I’m confident of my answer.”

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b. Recognizing the relationship between energy and charge

“Are charges used up in the production of light in a light bulb?” “Yes, because if you ever touch a

bulb that has been on for awhile, it is going to burn a little, and be hot. So the charge is moving around and then it converts to heat and then to light.

“I am going to say charge is used up, charges moving through the filament, because if charges weren’t used up, the battery would last forever.”

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c. Errors due to sequential reasoning

“I know that if this was like a motor or something (not a capacitor), I know that this would be greater, because it comes out of plus and goes to minus, and it hits this first.”

“Regarding the position, just looking at the pictures, the bulbs are both the same distance, the same position from the source, and here Bulb A is closer to the source of power. I figure that when the current goes through there it won’t be as great going to B.”

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d. Resistance of an individual circuit component

Bulb A glows much brighter than B. What would you observe if the bulbs were switched? “Bulb B would be brighter than

A. That is just common sense to me. I am guessing it is the positioning where they are, it is not the bulbs. If you switch B to A, B is going to be the brighter one and A is going to the dull position. This seems like a ‘gimme’.”

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e. Net resistance of series vs. parallel resistors

Is Bulb A brighter in Figure 1 or in 2, or the same in each?

Figure 1 Figure 2

“ . . . and then there are two in here in Figure 2. That is going to use more energy for each one of them, so A would be dimmer.”

“Bulb A will be dimmer in Figure 2 because the current is shared between three bulbs instead of two.”

CB

AA

B-

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f. Understanding of the circuit as a system

If a wire is attached around bulb B, predict what you would observe.

“I would think B would actually get dimmer, but I think bulb A would be the same brightness.”

“I think bulb A stays about the same brightness, because they would both be shared, yeah.”

A B

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g. Lack of knowledge of internal structure of a bulb

In which of the following circuits will the bulb light?

A B C D “B and C will light because the

circuit is complete in both of them and there is positive and negative. The only difference is it is placed on a different place on the bulb, but I don’t think that matters.”

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g. Lack of knowledge of internal structure of a bulb

Which bulbs will light? (A & C)

I do think that it is possible for the current to flow from A to B and then to C. I think that completes the circuit. I think maybe all bulbs will light actually.

“No bulbs will light. Some bulbs are connected right but that doesn’t make any difference because B isn’t.”

A

B

C

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h. Understanding the role of a compass in circuit analysis

Would the compass deflection be greater at A or at B?

“When you have a split in the wire, there would be a deflection in the opposite direction. But since these are going along the same path, I figured they would be in the same direction.”

B

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i. Imprecise vocabulary

“ . . . you could assume red being the highest energy or current or voltage or something.”

“When you pay for a household bill, you pay for the energy you use, because voltage is a measure of how much energy is used in a given time.”

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j. Capacitor charging and discharging

“Charging a capacitor, I think that as electricity passes through it, some of it is stored inside of the capacitor and then the rest of it is passed through to the rest of the circuit.”

“The battery is going to charge up this side, it will light this bulb A and whatever is left will stay in the capacitor until the capacitor is connected and empties into bulb B on the other side and then it cycles again.”

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k. Circuit analysis via color-coding

“It will measure how much electricity is going to the bulb, so brightest would be B, because it has red going to it. Next would be C because it has orange energy going to it, and last would be A, because it has yellow. I am sure I’m right.”

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l. Ammeters and Voltmeters

“Well, the ammeter wouldn’t actually measure the current through bulb B, because you placed it before bulb A.

“I think that the voltmeter would be measuring the current through Bulb A . I know that it wouldn’t be measuring the resistance, because when we were measuring the resistance, I think you actually need a resistor in there to measure resistance.”

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Confidence vs. Accuracy (Quantitative Results)

There was a significant correlation between confidence level and correctness of answer on the Pre-Assessment.

There was no correlation between confidence level and correctness of answer on the Post-Assessment. (There was a tendency to claim confidence even when wrong, and lack of confidence when right -- as if guessing.)

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Achievement Gains

There was no significant difference between Pre- and Post-Assessments scores (although scores actually declined.)

Achievement scores went from 5.1 to 4.8 (out of 15 items).

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Reasons for Poor Achievement?

Electricity concepts are abstract.

Time, discourse, multiple activities are required.

Teachers must have excellent instructional skills, including precise vocabulary themselves.

Curriculum developers must have classroom teaching experience.

Everyday experience (“rechargeable batteries”)

Misconceptions are persistent.

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CASTLE Curriculum

Results from research on similar circuits following instruction using the CASTLE Curriculum – using a Predict/Observe/Explain approach – have been far more promising

Examples: Color-coding strategies, the Hula Hoop analogy, and the concept of electric pressure difference (as an alternative to ‘potential difference’).

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Achievement Gains ??

Curriculum was re-designed to include more than one activity per concept.

Teachers had additional professional development and experience (same two teachers)

Sequence of activities, equipment choices, layout/format were reviewed

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Achievement Gains: Year 2 ??

Clinical interviews (qualitative results) often showed similar misconceptions

However, quantitative results (pre- and post-assessment) showed significant gains (n = 52) with no significant difference between two teachers

Pre-Assessment Mean: 4.46

Post-Assessment Mean: 9.28 p < 0.001