Which instrument is used to measure electrical current in a circuit?

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

Answer: (A)

Measuring current requires placing the instrument in series with the circuit so the same current flows through it. The ammeter is designed for this role, with very low internal resistance so it hardly alters the current. It directly measures the rate of flow of electric charges, typically in amperes. In contrast, a voltmeter is connected in parallel to measure voltage and is built with high resistance to avoid drawing current. An ohmmeter assesses resistance by applying a known current and reading the voltage, while a potentiometer is used to compare voltages or balance against a known emf, not to measure current directly.