Final answer:
If power is lost and then reapplied to a two-wire control device energizing a load, the reaction of the load depends on the control device's characteristics; some may keep the load energized while others may require manual resetting. Electrical safety systems, such as circuit breakers and proper grounding, protect against hazards.
Step-by-step explanation:
When a two-wire control device that was energizing a load loses power and then regains it, the particular outcome for the load depends on the nature of the control device and the configuration of the control circuit. If the control device is of a type that 'remembers' its state (such as a latching relay), the load will remain in its prior state once power is restored. However, in a simpler control circuit without such features, power loss may cause the device to revert to its default 'off' state, meaning the load will not be energized until the control device is manually reset or instructed to turn 'on' again.
Electrical safety features, including circuit breakers or fuses and grounding, are essential for preventing hazards such as electrical shock or thermal overload. Proper grounding ensures that the neutral wire is at zero volts and provides an alternative path for the current through the earth. This, along with circuit breakers, helps to protect both the electrical system and users from potential dangers.
In the event of a short circuit or wire insulation fault, as described in the referenced figures, a circuit breaker would trip to prevent excessive current flow, which could otherwise result in overheating of wires or appliance components. The three-wire system with a grounded case for the appliance is a critical component for maintaining electrical safety in these scenarios.