Which instrument is used to measure electric current?

Which instrument is used to measure electric current?

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

Answer: (A)

Measuring current requires placing a device directly in the path of the circuit so the same current flows through it as through the rest of the circuit. An ammeter is designed for this: it is connected in series with the load, and it has very low internal resistance so it doesn’t significantly alter the circuit’s current or voltage. When connected this way, it reads the current in amperes and shows how much charge is passing per second. The other instruments measure different quantities: a voltmeter connects across two points to read voltage and is built to have high resistance to avoid drawing current; an ohmmeter measures resistance by applying a small current or voltage to an isolated component; a wattmeter measures power by combining voltage and current to determine the real or apparent power in the circuit.

Measuring current requires placing a device directly in the path of the circuit so the same current flows through it as through the rest of the circuit. An ammeter is designed for this: it is connected in series with the load, and it has very low internal resistance so it doesn’t significantly alter the circuit’s current or voltage. When connected this way, it reads the current in amperes and shows how much charge is passing per second. The other instruments measure different quantities: a voltmeter connects across two points to read voltage and is built to have high resistance to avoid drawing current; an ohmmeter measures resistance by applying a small current or voltage to an isolated component; a wattmeter measures power by combining voltage and current to determine the real or apparent power in the circuit.