A2L Item 244

• Description: A loop of wire moves near a long current-carrying wire. When is the current in the loop clockwise?
• Goal: Hone skill at using Lenz's Law
• Source: 283-CTQsas36
• Keywords: Electromagnetism, Lenz's Law

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The question for students:

Consider the four situations below in which a wire loop lies in the plane of a long wire. In which case(s) is the induced current in the loop in the counterclockwise direction? [Note: if no velocity is indicated, the loop is stationary.]

1. A only
2. B only
3. C only
4. D only
5. A and B
6. C and D
7. All cases.
8. None of the above.

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Commentary for teachers:

Answer

1. Discussing each of the cases is valuable. Students have difficulty recognizing that the induced current is in a direction that causes the field of the induced current to compensate for the change in flux. Even when they nominally understand that, they have trouble reliably applying the right hand rule.

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