What instrument is used to measure current in a circuit?

An ammeter is specifically designed to measure electric current in a circuit. It is connected in series with the circuit components to ensure that the current flowing through the circuit passes through the ammeter. This allows it to accurately measure the flow of electric charge, typically expressed in amperes (A).

The ammeter works on the principle of measuring the voltage drop across a known resistance within the meter itself, allowing it to calculate the current based on Ohm's Law. In contrast, a voltmeter measures the voltage across components without affecting the current flow in the circuit, a resistor is used to limit current flow and does not measure it, and a switch controls the flow of current rather than measuring it. Thus, the ammeter is the appropriate instrument for measuring current directly.