What is a primary hazard when circuits are overloaded?

When circuits are overloaded, one of the primary hazards is the potential for fire. Overloading occurs when more current flows through a circuit than it is designed to safely handle. This excess current generates heat within the wires and the components of the circuit. If this heat accumulates to a level that exceeds the material's heat tolerance, it can ignite insulation materials, connectors, or other nearby combustible substances, leading to a fire.

This hazard highlights the importance of adhering to the electrical load ratings of circuits and ensuring that protective devices, such as circuit breakers and fuses, are appropriately selected and functioning. These devices are designed to interrupt the flow of electricity when a circuit becomes overloaded, helping to mitigate the risk of overheating and subsequent fire.

In contrast, the other options do not align with the reality of overloaded circuits. Increased energy efficiency typically results from properly designed and functioning circuits, rather than overloaded conditions. A reduction in electrical supply may happen due to protection devices tripping, but it does not directly describe a hazard associated with the state of overload. Improved circuit longevity is also an incorrect implication since consistently overloading a circuit damages components and leads to premature failure rather than longevity.