Question
Why do voltmeters have high input impedance?
Answer Options
- A) It improves the frequency response
- B) It allows for higher voltages to be safely measured
- C) It improves the resolution of the readings
- D) It decreases the loading on circuits being measured
Correct Answer: D
Explanation
A voltmeter’s fundamental job is to measure the voltage present at a point in a circuit without changing the circuit’s operating characteristics. All measurement instruments draw some current, which inevitably affects the voltage being measured (known as ‘loading’).
To minimize this effect, voltmeters are designed to have high input impedance. A high impedance means the meter draws only a tiny amount of current from the circuit under test. This ensures that the meter itself decreases the loading on circuits being measured, providing a more accurate and representative voltage reading.
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