What does a voltmeter measure?

A voltmeter is specifically designed to measure electric potential difference, commonly referred to as voltage, in units known as volts. When connected across two points in an electrical circuit, it provides a reading that indicates how much potential energy exists per unit charge. Understanding this measurement is crucial in electrical applications, as it helps assess the function of circuits, troubleshoot equipment, and ensure that electrical systems operate within safe and efficient voltage levels.

The other options pertain to different electrical units and measurements: current is measured in amperes, resistance in ohms, and power in watts, each requiring different instruments or meters for accurate readings.