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Question 167

Why do voltmeters have high input impedance?

  1. It improves the frequency response
  2. It allows for higher voltages to be safely measured
  3. It improves the resolution of the readings
  4. It decreases the loading on circuits being measuredCorrect answer

Explanation

A voltmeter is connected in parallel with the point being measured, so it forms a divider with the source impedance and draws current from the circuit. Making its input impedance high keeps that current negligible so the reading reflects the voltage that was there before the meter was attached.

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