GFCI receptacles trip when the current to ground is how many milliamperes or higher?

• A. 3 mA
• B. 6 mA
• C. 30 mA
• D. 60 mA

Answer: (B)

GFCI protection works by continuously comparing the current flowing in the hot conductor with the current returning in the neutral. If any current leaks out of the intended path—typically through a person touching a live surface or through moisture to ground—the two currents no longer match. The device is designed to trip when that imbalance reaches a very small level, around six milliamperes, to prevent a dangerous shock.

Choosing a threshold in this range is a balance: it’s low enough to detect dangerous leakage quickly and protect people, yet not so low that normal, tiny leakage currents from insulation imperfections or appliance internal paths cause nuisance trips. If the threshold were much higher (like 30 or 60 mA), a person could receive a much larger shock before the device interrupts the circuit. If it were much lower (like 3 mA), trips could happen frequently in normal operation.

So, the six milliamperes figure reflects the protection goal: trip for small ground faults to keep you safe, within a fraction of a second.