Which instrument measures potential difference in volts?

• A. Voltmeter
• B. Ammeter
• C. Ohmmeter
• D. Wattmeter

Answer: (A)

Measuring potential difference in volts is done with a voltmeter. A voltmeter is connected across the two points whose voltage you want to know, which is why it’s placed in parallel with the component or branch. Its very high internal resistance minimizes the current it draws, so it doesn’t alter the voltage you’re trying to measure. Volts are the unit of potential difference, so the device is built to read that quantity directly. In contrast, an ammeter measures current (amperes) and goes in series so it can sense the flow, an ohmmeter measures resistance (ohms) typically with the circuit de-energized, and a wattmeter measures power (watts) by combining voltage and current measurements.