What is the function of a voltmeter in a circuit?

A voltmeter is specifically designed to measure the electrical potential difference, or voltage, between two points in an electrical circuit. It is connected in parallel with the component or circuit segment whose voltage is being measured. When the voltmeter is properly connected, it displays the voltage across those points, allowing users to determine how much potential energy is available to push electric charge through the circuit.

The other options describe the functions of different instruments: a device measuring current would be an ammeter, while a multimeter could measure resistance. Power measurement typically requires a power meter or specific calculations involving voltage and current readings. Thus, the primary and accurate function associated with a voltmeter is voltage measurement.