By mistake a student connects a (nearly ideal) moving-coil voltmeter in series with a resistor, intending to measure current. With a 12 V source in the circuit, what reading does the voltmeter show?

12 V
0 V
4 V
6 V

Correct answer: 12 V

Solution

Because the ideal voltmeter's resistance is far larger than the series resistor, essentially the full 12 V drops across the voltmeter.

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