Which instrument is used to measure current in a circuit?

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

Answer: (A)

When you want to measure how much current flows through a circuit, you need a device that is placed in series so all the current passes through it. This is because current is the rate at which charge flows, and to know that rate you must have the measurement device carry the same current as the circuit. The instrument designed for this purpose is the ammeter, which is wired in series and has very low internal resistance so it doesn’t significantly affect the circuit’s current. In contrast, a voltmeter is connected in parallel to measure voltage and has high resistance to avoid drawing current; an ohmmeter applies a small current to measure resistance, not current in a live circuit; a multimeter can measure current but is a versatile tool used for multiple measurements. Therefore, the instrument used to measure current is the ammeter.