Electrician's Licensing Practice Exam

According to NEC Article 100, a device that opens and closes a circuit by nonautomatic means automatically closes for what condition?

1. A predetermined undercurrent

2. A predetermined overcurrent

3. Manual control

4. Emergency shutdown

The correct answer is: A predetermined overcurrent

The correct answer pertains to the concept of a device that operates by nonautomatic means, where it is designed to open and close a circuit based on specific electrical conditions. In this context, a device that opens a circuit due to a nonautomatic trigger will automatically close again when a predetermined overcurrent condition is detected. This is significant because many electrical devices, such as circuit breakers or certain safety devices, are designed to interrupt the current flow in response to an overcurrent situation, which indicates a potential fault or overload. By automatically closing under this condition once the fault is cleared or resolved, the circuit can be restored to normal operation without requiring manual intervention. The other options involve different operational functions: a predetermined undercurrent would not typically signal an automatic closing; manual control implies direct human intervention, which is not automatic; and emergency shutdown is a scenario that may not trigger the same automatic closure response depending on the specific device's design and purpose. Therefore, understanding how and when a device is meant to operate is essential for anyone studying electrical systems and the National Electrical Code (NEC).