Final answer:
The 'one-hand rule' is a safety practice to minimize shock hazards when working with electrical equipment. It prevents establishing a current path across the body, particularly the heart. This technique, along with devices like circuit breakers and three-wire systems, is fundamental to electrical safety.
Step-by-step explanation:
The "one-hand rule" when operating electrical equipment is a safety technique to minimize shock hazards. The basis behind this rule is that by keeping one hand at your side or in your pocket, you're less likely to create a path for electrical current to travel through your body, particularly across the heart, which can be fatal. When you use only one hand, the chance of current passing from one hand through your chest to the other hand or foot is reduced, thus minimizing the risk of serious injuries or death.
Electrical appliances, circuit breakers, and fuses are rated in amperes (or amps), which are indicators of the electrical current they require or can safely manage. These devices, along with transformer systems such as step-up and step-down transformers, are all designed to keep electrical safety in mind. A three-wire system, which includes live, neutral, and ground wires, is one such safety design to avoid thermal and shock hazards by providing a safe pathway for any fault current to be safely dispensed of. Furthermore, when touching a power transmission line as a final check, professionals use the back of their hands. This ensures that if there is any remaining voltage, the natural reaction of the muscles contracting will pull the hand away rather than grabbing onto the line, which is a possible reaction if the palm or fingers were used to touch it.