A2L Item 239

• Description: Identify the situations having an induced current flowing clockwise.
• Goal: Reason with Lenz's Law
• Source: 238-730 Lenz's Law 2
• Keywords: Electromagnetism, Flux, Lenz's Law

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The question for students:

For which of the following situations will the current flow clockwise? <table

A) A conducting rectangular loop falls from rest into a magnetic field directed out of the page.

B) A thin metal strip slides down parallel rails elevated at an angle q. A constant B field is directed vertically upward.

C) A conducting loop moves in a magnetic field produced by an infinite current-carrying wire.

</table>

1. No situations
2. A
3. A and B
4. A and C
5. A, B, and C

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Commentary for teachers:

Answer

(4) There is usually a lot of confusion with Lenz’s Law. It is important to determine what students are using to decide the direction of the current. Some students despair of ever figuring it out and just guess. Examining the microscopic motion of charges often helps.

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