Which instrument measures electric current?

An ammeter is the instrument specifically designed to measure electric current in a circuit. It operates by allowing the current to pass through it and produces a reading that reflects the amount of current flowing, typically measured in amperes. Ammeters are often connected in series within the circuit, ensuring that all of the current flows through the device for an accurate measurement.

Other instruments, like ohmmeters and voltmeters, serve different purposes. An ohmmeter measures resistance and requires the component to be isolated from power, while a voltmeter measures voltage across two points in a circuit and is usually connected in parallel. A wavemeter is used to measure the frequency of radio waves and is not involved in measuring current at all. Therefore, when needing to measure electrical current, the ammeter is the precise tool for the job, making it the correct answer.