What instrument is primarily used to measure current in a circuit?

The tool that is primarily used to measure current in a circuit is the ammeter. An ammeter is specifically designed to measure the flow of electric current in amperes (A). It is connected in series within the circuit, allowing it to accurately measure the amount of current passing through that segment of the circuit.

In contrast, a voltmeter is used to measure voltage across a component or circuit, and it is connected in parallel. The ohmmeter measures resistance, which is a different electrical characteristic, while a multimeter can measure multiple parameters, including voltage, current, and resistance, but is not dedicated solely to current measurement. Therefore, while a multimeter can measure current, the ammeter specifically excels in that role, making it the correct instrument for this purpose.