What device is used to measure electrical current?

An ammeter is specifically designed to measure electrical current, which is defined as the flow of electric charge in a circuit. It operates by being connected in series with the circuit, allowing the current to pass through it. This device provides a reading that indicates the amount of current flowing, usually expressed in amperes. The construction of an ammeter allows it to safely measure current without significantly affecting the circuit's operation.

In contrast, a capacitor is used to store electrical energy, a transformer changes the voltage of electrical energy, and a voltmeter measures electrical potential difference or voltage across two points in a circuit. Each of these devices serves a distinct purpose and is designed for specific electrical measurements, but only the ammeter directly measures current.