Which device detects unequal current between hot and neutral and disconnects power?

Which device detects unequal current between hot and neutral and disconnects power?

• A. Ground-fault circuit interrupter (GFCI)
• B. Residual current device (RCD)
• C. Arc-fault circuit interrupter (AFCI)
• D. Overcurrent protective device (OCPD)

Answer: (A)

A device that protects people by sensing leakage current uses a hot and neutral current monitor and looks for any imbalance between them. If some current should be returning via neutral but instead leaks to ground (through a person or faulty path), the two conductors no longer carry the same current. The sensing circuit detects this difference and instantly trips the switch, cutting power to prevent shock. This is exactly how a ground-fault circuit interrupter operates: it detects unequal current between hot and neutral and disconnects power. The other devices work to protect in different ways. An arc-fault interrupter looks for patterns caused by arcing, not just leakage to ground. An overcurrent protective device trips when the current is too high due to overload or a short circuit, not because of a ground fault. An RCD is the general term for this type of residual-current protection used in many regions, while the GFCI is the U.S. version of that same function.

A device that protects people by sensing leakage current uses a hot and neutral current monitor and looks for any imbalance between them. If some current should be returning via neutral but instead leaks to ground (through a person or faulty path), the two conductors no longer carry the same current. The sensing circuit detects this difference and instantly trips the switch, cutting power to prevent shock. This is exactly how a ground-fault circuit interrupter operates: it detects unequal current between hot and neutral and disconnects power.

The other devices work to protect in different ways. An arc-fault interrupter looks for patterns caused by arcing, not just leakage to ground. An overcurrent protective device trips when the current is too high due to overload or a short circuit, not because of a ground fault. An RCD is the general term for this type of residual-current protection used in many regions, while the GFCI is the U.S. version of that same function.