What type of device uses a solenoid to operate a switch that can open or close another circuit?

A relay is a device that uses an electromagnet, typically in the form of a solenoid, to operate a switch. When an electric current passes through the coil of the solenoid, it generates a magnetic field that actuates the switch, allowing it to open or close another circuit. This feature makes relays extremely useful for controlling high power circuits with low power signals, providing electrical isolation and enabling automation in various applications.

In contrast, a capacitor stores electric charge, a resistor limits the flow of current in a circuit, and a transistor typically acts as a switch or amplifier but operates on a different principle involving semiconductor materials and does not utilize a solenoid in the same way a relay does. Understanding the role of each component helps clarify why the relay is the correct choice for operating a switch via an electromagnet.