alleryStart learning →Which null measurement device is used to measure a potential difference?
AThe Wheatstone bridge
BThe potentiometer
CThe analog ammeter
DThe digital ohmmeter
Answer & Solution
Correct answer: B. The potentiometer
1. A potentiometer is the null device built for measuring potentials.
2. It sets a known IR drop along a wire against the unknown emf until a galvanometer reads zero.
3. The Wheatstone bridge is also a null device, but the quantity it determines is resistance.
4. An ammeter and an ohmmeter both need current to operate, so neither is a null instrument.
_Source: OpenStax College Physics (CC BY 4.0), Ch 21 "Circuits and DC Instruments", section 21.5 Null Measurements_
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