What safety device ensures that electrical circuits are not overburdened?

The safety device that ensures electrical circuits are not overburdened is a circuit breaker or fuse. Both of these devices serve to protect electrical circuits from excess current that could lead to overheating or damage.

When the current flowing through a circuit exceeds its designed limit, the circuit breaker will trip or the fuse will blow, interrupting the flow of electricity and preventing potential hazards such as electrical fires or equipment failure. This proactive safety measure is crucial in residential, commercial, and industrial settings, as it safeguards both the electrical infrastructure and the connected devices.

The other devices listed do not perform this protective function. A power valve is not related to electrical circuits but rather pertains to fluid dynamics, typically found in hydraulic systems. A relay is an electromechanical switch that is used to control a circuit but does not inherently provide overload protection. A capacitor is an electronic component that stores electrical energy and is used for power factor correction or energy storage, but does not prevent circuit overload.

Thus, the circuit breaker or fuse is essential for maintaining safety in electrical circuits by ensuring they operate within their intended capacity.