A2L Item 251

• Description: Identify the circuit that is equivalent to the initial behavior of an RC circuit.
• Goal: Reason regarding capacitors
• Source: 283-585 RC equivalent circuit at early time
• Keywords: Electromagnetism, Circuits, Capacitors, Reasoning

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The question for students:

Consider the following circuit.

The capacitor is uncharged when the switch is closed at t=0. Which circuit is equivalent to this circuit for the instant immediately after the switch is closed?

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Commentary for teachers:

Answer

(3) Some students misunderstand the statement that capacitors behave initially as a short circuit and select #1 or #2.

This item is best used in conjunction with the next 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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