Ham Radio General Class Practice Test

Which wire or wires in a four-conductor line cord should be attached to fuses or circuit breakers in a device operated from a 240-VAC single-phase source?

1. Only the hot wires

2. Only the neutral wire

3. Only the ground wire

4. All wires

The correct answer is: Only the hot wires

In a typical 240-VAC single-phase system, there are usually two hot wires (often referred to as "Line 1" and "Line 2") and potentially a neutral and ground wire. When protecting an electrical device with fuses or circuit breakers, it's crucial to ensure that protection is appropriately applied to prevent overcurrent situations that can lead to equipment damage or fire hazards. Attaching fuses or circuit breakers to only the hot wires is the correct approach because these wires carry the current to the device, and if either of these wires experiences overload, the breaker or fuse will disconnect power flow, thus providing protection. In contrast, the neutral wire serves as a return path for the current and is not typically fused in a 240-VAC system because it is not intended to carry current under normal operation; under fault conditions, it may carry current, but protecting it with a fuse would not prevent overload situations on the hot wires. The ground wire's purpose is to provide a safe path for fault currents to return to the ground and is not involved in circuit protection circuits. Therefore, it also should not be connected to fuses or circuit breakers. Keeping this in mind, a rational choice for fuse or circuit breaker connection in a 240