Meters and troubleshootingQuestion 721 of 1506

A polarity-sensitive moving-coil meter movement is connected to an AC source. What does the needle do?

It only vibrates, with no useful reading
It reads the peak value of the AC, just like a digital meter would
It settles on the average value of the AC wave
It swings to full scale and stays there at all times

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Correct answer: It only vibrates, with no useful reading

The torque reverses with the current direction, so the needle just shakes.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 8.1: What is a Meter?

Questions last reviewed: 18 October 2026

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