Which of the following elements serves to protect circuits in electrical systems?

The circuit breaker is the element that serves to protect circuits in electrical systems. Its primary function is to automatically interrupt the flow of electricity in the event of an overload or short circuit, thereby preventing damage to the wiring and connected devices. By breaking the circuit, it helps ensure safety and reduces the risk of fire hazards that can arise from excessive current.

Circuit breakers are designed to respond to specific conditions in the electrical system, making them essential for maintaining safe operation. Unlike other elements listed, a switch merely controls the flow of electricity without protection features, a relay utilizes an electromagnetic mechanism to control a circuit rather than provide protection, and a transformer adjusts voltage levels but does not offer circuit protection. Thus, the circuit breaker stands out as the crucial component dedicated to safeguarding electrical systems.