What does a voltmeter measure?

A voltmeter measures the voltage across two points in an electrical circuit. Voltage, also known as electric potential difference, is the force that pushes electric charges through a conductor. By connecting a voltmeter in parallel with the components whose voltage you want to measure, the instrument can determine the difference in electric potential between those two points.

This measurement is essential for understanding how much energy is available to move charges through the circuit, which is crucial for analyzing circuit behavior and ensuring proper functionality. The voltmeter's design allows it to provide readings without significantly affecting the overall circuit operation.

The other options refer to different electrical parameters: current is measured in amperes, resistance in ohms, and power in watts, each requiring specific instruments like ammeters, ohmmeters, and wattmeters respectively. This distinction helps clarify the unique purpose and function of a voltmeter in electrical measurements.