Which quantity does a voltmeter measure?

• A. Current
• B. Resistance
• C. Voltage
• D. Power

Answer: (C)

The quantity being tested is the electrical potential difference, or voltage. A voltmeter is designed to measure the difference in electric potential between two points, so you connect it across the component or portion of the circuit you want to inspect. Because it should not significantly alter the circuit, a voltmeter is built with very high input resistance, which minimizes current flow and allows it to sense the potential difference without drawing much current. The reading is given in volts.

In case you’re comparing with other instruments: an ammeter measures current and is placed in series with a circuit so it can track the flow of electrons through the path. An ohmmeter measures resistance by applying a small test current or voltage and observing the response. A wattmeter measures power, which is the product of voltage and current (P = V × I).