Which instrument would you use to determine the current flowing in a wire?

• A. Ammeter
• B. Voltmeter
• C. Ohmmeter
• D. Continuity tester

Answer: (A)

To determine current in a wire, you need an instrument that reads the rate of flow of electric charges and is placed in series with the circuit so all the current passes through it. An ammeter is designed for this: it has very low internal resistance and is wired in series, so it measures the current without significantly altering the circuit. In contrast, a voltmeter measures voltage and is connected in parallel with a component, and an ohmmeter measures resistance by applying its own current when the circuit is not powered. A continuity tester checks whether a path exists, but it doesn’t quantify how much current is flowing. Therefore, the correct instrument is the ammeter.