Final answer:
Ordinary circuit breakers and fuses act too slowly to protect against electric shocks because they are designed to prevent thermal hazards rather than the lower-level current differences that can cause shock. Devices like GFIs are thus used to rapidly detect and prevent shock hazards.
Step-by-step explanation:
Why Ordinary Circuit Breakers and Fuses Are Ineffective in Preventing Shocks
Ordinary circuit breakers and fuses are designed to protect against thermal hazards such as fires, not electric shocks. The reason ordinary circuit breakers and fuses are ineffective in preventing shocks is option b) They act too slowly.
Circuit breakers and fuses are safety devices that interrupt the flow of excessive current to prevent damage from overheating and fires. However, the level of current that can cause a shock hazard to humans is much lower than the thresholds set for these devices to trip. Therefore, electric shock can occur without reaching the current level that would trigger a circuit breaker or fuse to shut off the flow of electricity.
A ground fault interrupter (GFI) is a device specifically designed to prevent shock by rapidly detecting very small differences in current between the live and neutral wires, indicating a potential path of current through a person. This trip indicates the GFI is functioning correctly to protect against electric shock, rather than a thermal hazard.