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Concepts Of Physics MCQ Edition [Volume 2]PhysicsAlternating Current

Which of the following instruments can be used to measure the AC voltage across a resistance?

Options

  1. AA moving-coil galvanometer
  2. BA hot-wire voltmeter
  3. CA moving-magnet galvanometer
  4. DA potentiometer

Correct answer

B. A hot-wire voltmeter

Step-by-step solution

An alternating current (AC) reverses its direction periodically. The average value of AC over a complete cycle is zero. Instruments like the moving-coil galvanometer, moving-magnet galvanometer, and potentiometer measure the average value of voltage or current. If connected to an AC circuit, their pointers will not deflect because the average AC voltage is zero. A hot-wire voltmeter works on the principle of the heating effect of electric current, given by H = V^2 R t . Since the heat produced is proportional to th

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