What instrument is used to measure potential difference in a circuit?

The voltmeter is the instrument designed specifically for measuring potential difference, also known as voltage, in an electrical circuit. It operates by connecting its probes across the two points in the circuit where the voltage needs to be measured. The voltmeter's internal resistance is very high to ensure that it does not significantly affect the circuit's operation, allowing for an accurate reading of the potential difference.

In contrast, an ampermeter measures the current flowing through a circuit, with the focus on amperage rather than voltage. An ohmmeter is used to measure resistance in an electrical component or circuit. A multimeter can measure voltage, current, and resistance, but its classification covers a broader range of functions than just measuring potential difference. While the multimeter could be utilized to measure voltage, the specific instrument that stands out for this purpose is primarily the voltmeter.