An arc-fault protective device that recognizes arcing characteristics and de-energizes the circuit when an arc fault is detected is called what?

• A. circuit breaker
• B. arc-fault circuit interrupter
• C. safety switch
• D. ground-fault circuit interrupter

Answer: (B)

An arc-fault circuit interrupter. This device is designed to detect the distinctive electrical signature of arcing—irregular, high-frequency current fluctuations and noise—and automatically shut off the circuit to prevent an arc from causing a fire. It differs from a normal circuit breaker, which trips for overloads or short circuits but may not sense arcing; a safety switch is just a disconnect; and a ground-fault circuit interrupter protects against shock by sensing current imbalance, not arc faults. AFCIs (often as breakers or integrated into panels) are specifically aimed at preventing fires from arc faults in wiring and devices.