Get Wired 102 Introduction To The Basic Installation Of Lighting Fixtures And Branch Circuits Practice Test

What is the primary function of a GFCI device?

Trip when ground-fault current exceeds a small threshold Provide surge protection Switch off power to the entire building in a fault Detect overcurrent in any conductor

Correct Answer:

Trip when ground-fault current exceeds a small threshold

Explanation:

The main function of a GFCI is to protect people from electric shock by sensing any leakage of current to ground and interrupting the circuit quickly. It does this by continuously comparing the current flowing through the hot conductor and the return current on the neutral conductor. If the two aren’t equal, that difference means some current is escaping to ground (often through a person), and the device trips within milliseconds at a very small threshold, typically around a few milliamps. This rapid cut-off is what prevents serious shocks. It isn’t meant for surge protection, it doesn’t shut off power to the entire building in a fault, and it doesn’t monitor overcurrent in a conductor—that’s the job of other protective devices.

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