Which device is used to measure electrical potential difference?

• A. Ammeter
• B. Voltmeter
• C. Thermometer
• D. Multimeter in resistance mode

Answer: (B)

Measuring electrical potential difference between two points requires a voltmeter. This instrument is connected across the two points so it reads the energy difference per unit charge, and it has a very high internal resistance to minimize drawing current from the circuit, so it doesn’t disturb the measurement.

An ammeter, by contrast, is designed to measure current and is placed in series so it carries the circuit current. A thermometer measures temperature, unrelated to electrical quantities. A multimeter set to resistance mode measures how much a component resists current (its resistance), not the voltage across two points.