Final answer:
The subject relates to engineering and focuses on electrical safety systems, specifically grounding in electrical systems. It covers the role of grounding in preventing shock and thermal hazards and mentions safety devices like circuit breakers and fuses within a three-wire system.
Step-by-step explanation:
The question relates to the electrical safety systems and practices for grounding in electrical systems as described in codes and standards, particularly within the context of the National Electrical Code (NEC).
To understand this concept, one must recognize the importance of having a grounded system to ensure the safety of both the electrical appliances and the individuals using them. Grounding helps to prevent shock hazards by ensuring that the metal case of an appliance is at zero voltage, providing a path for the current to return to the ground in case of any fault. Additionally, devices like circuit breakers and fuses are used to protect against thermal hazards by interrupting excessive currents that could otherwise cause overheating and possibly a fire. The illustration provided indicates that a three-wire system is used which includes live/hot, neutral, and ground wires, forcibly connecting the neutral wire to the earth both at the voltage source and user's location.
In the provided scenario, where there is a short circuit to the grounded metal case of an appliance and a person touching the case has a 3.00 kΩ resistance to earth, it's essential to determine the safety of that situation. If the case of an appliance becomes live due to a fault, the resistance path to earth through a person could become part of the circuit, potentially leading to a dangerous electric shock. This is why the grounding system must function effectively to provide a safer, low-resistance path directly to the earth.