__________ are required to prevent shock hazards that occur from touching metallic parts of an electrical system.

Grounding circuits are crucial in preventing shock hazards that can arise from accidental contact with metallic parts of an electrical system. When electrical systems are grounded properly, any fault current (such as that which might occur if a live wire comes into contact with a metal casing) is directed safely into the ground. This significantly reduces the risk of electrical shock to individuals who may accidentally touch exposed metallic parts.

The grounding system acts as a protective pathway for stray electricity, ensuring that any excessive current is rapidly dissipated. In scenarios where there is a fault, the grounded circuits help facilitate the operation of protective devices like circuit breakers, leading them to trip and disconnect the electrical supply before someone is harmed.

While insulation materials can also help protect against electrical shock by providing a barrier between conductive parts and users, they do not address faults that could lead to exposed conductive surfaces. Transfer switches and fuses are important components in electrical systems, but they serve different functions such as switching power sources or protecting against overcurrent, rather than specifically preventing shock hazards from contact with metallic parts.