Which of the following is used to measure voltage?

A voltmeter is specifically designed to measure voltage, which is the electrical potential difference between two points in a circuit. It typically connects in parallel with the component being measured to ensure that it accurately reflects the voltage across that component. This design is essential, as connecting it in series could affect the circuit's operation and yield an incorrect reading.

The other measuring devices listed serve different purposes: an ammeter measures current, a wattmeter measures power, and an ohmmeter measures resistance. Each of these instruments is tailored to assess specific electrical parameters, which is why their use is distinct and precise in electrical testing and diagnostics. Understanding the specific function of a voltmeter is crucial for anyone involved in electronics, as accurate voltage readings are fundamental for troubleshooting and designing circuits.