A2L Item 254

• Description: Identify the circuit that is equivalent to the behavior of an RL circuit after a long time.
• Goal: Reasoning regarding inductors
• Source: 283-750 LR equivalent at time = infinity
• Keywords: Inductors, Reasoning, Electromagnetism, Circuits

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The question for students:

Consider the following circuit.

The switch is closed at t=0. Which circuit is equivalent to this circuit as t approaches infinity?

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Commentary for teachers:

Answer

(3) Some students misunderstand the statement that inductors behave as a short circuit after a long time and select #1 or #2.

This item is best used in conjunction with the previous one. Both should be asked before discussion of either to reveal whether students just have the behaviors reversed or evidence a more serious problem.

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