Final answer:
GFCIs detect differences in current between the hot conductor and the Grounded (neutral) conductor to prevent shock hazards. They are triggered when a leakage current exceeds 5 mA, indicating a deviation from the safe path of the electricity.
Step-by-step explanation:
GFCIs (Ground Fault Circuit Interrupters) are designed to sense any difference in current between the supply on the ungrounded (hot) conductor in a circuit, and the Grounded (neutral) conductor. They operate on the principle of electromagnetic induction and monitor the current flow in the live/hot and neutral wires. A GFCI intervenes and interrupts the circuit when it detects a difference in current, typically if a leakage current exceeds 5 mA, indicating a potential shock hazard. The three-wire system employed in modern appliances ensures that the neutral wire and case of the appliance are grounded, further protecting against thermal and shock hazards.