What is the primary function of a relay?

The primary function of a relay is to open and close electrical contacts. A relay is an electromechanical switch that uses an electromagnet to operate a set of contacts. When an electrical current flows through the coil of the relay, it generates a magnetic field that either attracts or repels a movable armature. This action opens or closes the contacts connected to the circuit, allowing control of a larger current or different voltage level with a smaller control signal. This operation is particularly useful in automation and control systems, where it can enable or disable devices or circuits remotely and safely.

The other options do not accurately describe the purpose of a relay. Increasing electrical resistance pertains to resistive components, while storing electrical energy is a function associated with capacitors or inductors. The conversion of light energy into electrical energy describes the function of photovoltaic cells in solar panels, which is entirely different from the operation of a relay. Understanding the mechanism and purpose of a relay is crucial for effective electrical circuit design and operation.