What might happen if a circuit breaker fails?

A circuit breaker is designed to protect an electrical circuit from overloads and short circuits, acting as a safety device that interrupts the flow of electricity when it detects unsafe conditions. If a circuit breaker fails, it may not trip when there is an overload or a fault in the circuit. This failure can lead to an increased risk of electrical fires, as excessive current can pass through wiring that is not equipped to handle it. When wires overheat due to high current, the insulation can break down, which risks igniting nearby combustible materials.

In contrast, the other options do not accurately reflect the consequences of a circuit breaker failing. If the circuit remains protected, this implies the breaker is functioning, which contradicts the assumption of failure. Continued normal operation of appliances is misleading as it could lead to dangerous conditions without the interrupted current that a functioning breaker provides. Improved power efficiency is not a plausible outcome of a circuit breaker failure, as the main concern is the safety and protection of the electrical system rather than efficiency. Thus, the correct answer highlights the serious implications of such a failure in terms of safety hazards.