Which instrument is used to measure current?

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

Answer: (C)

Measuring current requires a device that the same amount of charge flows through, so it must be placed in series with the circuit. The ammeter is designed for this role; when it sits in series, the current in the circuit passes through the meter, and its reading reflects the circuit current. To avoid altering the circuit’s behavior, an ideal ammeter has very low internal resistance, so it doesn’t drop significant voltage.

For context, a voltmeter is connected in parallel to a component to measure voltage and is built with high resistance to draw as little current as possible. An ohmmeter measures resistance by injecting a small current when the circuit is unpowered. A wattmeter measures power by combining voltage and current readings (P = VI).

So, the instrument used to measure current is the ammeter.