Which instrument is used to measure voltage in a circuit?

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

Answer: (B)

To measure voltage, you use a voltmeter. A voltmeter is designed to measure the potential difference between two points in a circuit, which is what voltage represents. It’s connected in parallel across the component or across the two nodes where you want to know the voltage, so it doesn’t alter the current flowing through the circuit. Its high internal resistance means it draws only a tiny amount of current, keeping the circuit behavior essentially unchanged while you read the voltage in volts.

Think of it this way: voltage tells you how much push there is to move charges from one point to another, and a voltmeter is the instrument that senses that push without loading the circuit. In contrast, an ammeter measures current by being placed in series (it has very low resistance so it doesn’t drop much voltage), an ohmmeter measures resistance (usually with the circuit powered off and isolated), and a wrench is simply a tool, not an electrical measuring device.