What is the internal resistance of a 20,000 ohm/volt voltmeter set to its 5 V range_____________?
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Answer: B. 100,000 Ω
Explanation
The internal resistance of a voltmeter is calculated by multiplying its ohms-per-volt rating by the selected voltage range. Multiplying twenty thousand ohms per volt by the five volt range setting results in a total internal meter resistance of one hundred thousand ohms. Higher ohms-per-volt sensitivity ratings ensure the voltmeter draws minimal current from the circuit under test, improving measurement accuracy. Analog voltmeters utilize sensitive galvanometer movements connected in series with large multiplier resistors to measure voltage levels. Voltmeter sensitivity is expressed in ohms per volt, representing the reciprocal of the full-scale deflection current of the movement. Loading effect occurs when a voltmeter's internal resistance is not significantly higher than the resistance of the circuit being measured.
A resistance of 20,000 ohms reflects only the base ohms-per-volt rating without accounting for the selected 5 V range multiplier. A resistance of 200,000 ohms represents the correct calculation if the voltmeter range setting were doubled to ten volts. A value of 1,000,000 ohms corresponds to a fifty-volt range setting rather than the specified five volt measurement configuration.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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