Understand the concept
A GFCI compares the current flowing in the outgoing and returning conductors. A difference can indicate current flowing along an unintended path, so the device rapidly interrupts the circuit.
Overcurrent protection and GFCI protection have different purposes: a breaker protects against excessive current; a GFCI focuses on ground-fault shock risk. Neither makes live work safe.
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Practice task
In a supervised lab, identify LINE versus LOAD markings and the test/reset controls on a training device. Follow the manufacturer instructions and applicable electrical code.
CHECK YOUR UNDERSTANDING