Which instrument is used to measure voltage?

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

Answer: (B)

Voltage is the electrical potential difference between two points, and a voltmeter is built specifically to read that difference. It’s connected across the component or section you want to measure, so it sits in parallel with it. That parallel hookup lets the meter measure the potential difference without forcing current through the circuit, which would alter the voltage you're trying to observe. To avoid changing the circuit behavior, the voltmeter is designed with very high internal resistance, so it draws only a tiny amount of current.

Other instruments have different jobs. An ammeter is used to measure current and is placed in series with the circuit, and it has very low resistance to minimize voltage drop as current flows. An ohmmeter measures resistance by applying a small test current and reading the resulting voltage, typically when the circuit is unpowered. A wattmeter measures power, which is the product of voltage and current, and it uses separate pathways to determine both quantities, not just the voltage alone.

So, when you need to know the voltage across points in a circuit, the voltmeter is the appropriate tool.