Final answer:
A breaker with two hot conductors under one screw is not a defect if it is designed to accept two hot conductors, per manufacturer specifications. Safety issues arise when breakers not intended for multiple conductors are used improperly. The importance of this is heightened by the role of grounded systems in electrical shock prevention and circuit protection.
Step-by-step explanation:
A breaker with two "hot" conductors under one screw is not considered a defect, if that breaker is specifically listed to accept two "hot" conductors. Circuit breakers and electrical panels are designated by the manufacturer regarding how many conductors can be safely installed under the terminal screws. If the breaker is only listed for one conductor and two are installed, it's a serious safety hazard that could potentially lead to overheating and electrical failure.
In some cases, breakers are designed to accept multiple conductors, but this should only be done in accordance with the manufacturer's specifications and local electrical codes to ensure safety. The importance of these considerations can be illustrated by scenarios involving improper grounding or damaged insulation of wiring. As shown in Figure 23.34 and Figure 10.45, a proper ground connection can prevent severe electric shock if the insulation on live/hot wires becomes worn and contacts the metal case of an appliance.
In such situations, an intact ground wire will enable the circuit breaker to trip, indicating a need for repair and preventing potential electric shock. Furthermore, the transition from two-wire systems to three-wire systems, with dedicated ground wires, showcases advancements in electrical safety by reducing the risks associated with faulty insulation and providing a path for excess current to safely dissipate into the earth.