What is the primary use of a voltmeter?

The primary use of a voltmeter is to measure the electrical potential difference between two points in a circuit. This measurement is crucial for understanding how much voltage is being applied across components, which in turn affects the behavior of the circuit.

When a voltmeter is connected in parallel with the component whose voltage you want to measure, it can give you a direct reading of the potential difference. This is fundamental in determining whether components are receiving the appropriate voltage, assessing circuit performance, and troubleshooting electrical issues.

The other options focus on different measurements that are not the primary function of a voltmeter. For instance, measuring current is the function of an ammeter, while measuring resistance is done with an ohmmeter. Frequency measurement is associated with devices like frequency counters or oscilloscopes, not voltmeters. Understanding these distinctions can clarify the specific roles of different measuring instruments in electrical applications.