CSLB Class B General Contractor's License Practice Exam

What happens if 14-gauge wire is used on a 20-amp circuit?

1. It causes a fire hazard

2. It runs efficiently

3. It trips the circuit breaker immediately

4. It can overheat

The correct answer is: It can overheat

Using 14-gauge wire on a 20-amp circuit is generally not recommended due to safety risks. The correct answer highlights that 14-gauge wire can overheat when carrying more current than it is rated for. Specifically, 14-gauge wire is typically rated for a maximum of 15 amps, while a 20-amp circuit requires wiring that can safely handle greater current without risk of overheating. When a 14-gauge wire is subjected to the higher load from a 20-amp circuit, it can lead to excessive heat buildup within the wire. This overheating presents a significant risk, as it may damage the wire's insulation over time and potentially lead to an electrical fire. The other options address different scenarios that may not be the immediate implications of using 14-gauge wire on a 20-amp circuit. While a fire hazard is a valid concern, it is a more indirect consequence of overheating rather than a direct immediate result. The circuit breaker may not trip immediately because the overload could take time to manifest, and while the wire might not run efficiently due to excessive heat, the term "efficiently" does not accurately capture the critical safety issues involved.