Which instrument is used to measure current?

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

Answer: (A)

Measuring current requires an instrument that tracks how much charge is moving each second, expressed in amperes. The ammeter is built for this purpose, and it’s placed in series with the circuit so the same current flows through it as through the rest of the circuit. Because it needs to carry the circuit current, it is designed with very low internal resistance to avoid dropping voltage or altering the current.

In contrast, a voltmeter measures voltage and is connected in parallel, with high internal resistance to minimize its influence on the circuit. An ohmmeter measures resistance by applying a small current and reading the resulting voltage drop, and is typically used on de-energized components. A wattmeter measures power (the product of voltage and current, accounting for phase in AC circuits), not just current.