Which instrument measures electrical potential difference (voltage)?

Which instrument measures electrical potential difference (voltage)?

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

Answer: (B)

Measuring electrical potential difference requires a device designed to read volts and to draw as little current from the circuit as possible. That potential difference, or voltage, is the difference in electrical pressure between two points. A voltmeter is built with very high internal resistance, so it minimizes current draw and can be placed in parallel across the two points you want to compare without significantly altering the circuit. When connected in parallel, it measures the voltage between those points. In contrast, an ammeter is used to measure current and is placed in series, since it must carry the circuit current. An ohmmeter measures resistance by applying a known current and reading the voltage drop—usually when the circuit is powered off. A barometer measures atmospheric pressure, not electrical quantities. So, the instrument that measures electrical potential difference is the voltmeter.

Measuring electrical potential difference requires a device designed to read volts and to draw as little current from the circuit as possible. That potential difference, or voltage, is the difference in electrical pressure between two points. A voltmeter is built with very high internal resistance, so it minimizes current draw and can be placed in parallel across the two points you want to compare without significantly altering the circuit. When connected in parallel, it measures the voltage between those points.

In contrast, an ammeter is used to measure current and is placed in series, since it must carry the circuit current. An ohmmeter measures resistance by applying a known current and reading the voltage drop—usually when the circuit is powered off. A barometer measures atmospheric pressure, not electrical quantities. So, the instrument that measures electrical potential difference is the voltmeter.