What is the purpose of a relay in electrical circuits?

The purpose of a relay in electrical circuits is to control a larger power circuit using a smaller current. Relays function as electrically operated switches that allow a low-power signal to activate a high-power circuit, enabling control of heavy loads without requiring direct human interaction or heavy-duty switches. This is particularly useful in automation systems or in scenarios where switching needs to be done from a distance. When a small current passes through the relay's coil, it creates a magnetic field that pulls a switch closed or opens it, thus managing the larger current flowing through the circuit effectively and safely.

The other choices do not accurately represent the function of a relay. Generating electricity is a function of generators or power plants, while fuses serve the purpose of protecting circuits from excessive current by breaking the circuit when a certain threshold is exceeded. Measuring electrical resistance is done using instruments like ohmmeters, not relays. Thus, the correct role of a relay revolves around facilitating control in larger electrical systems using minimal current, leading to increased safety and efficiency in electrical applications.