North Carolina Home Inspector Practice Exam

What size copper wire is required for a 40-amp breaker?

1. 6

2. 8

3. 10

4. 12

The correct answer is: 8

The size of the copper wire required for a 40-amp breaker is a crucial aspect of electrical safety and performance. When determining the appropriate wire gauge, it’s essential to consider the ampacity, which is the maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration. For a 40-amp circuit, the National Electrical Code (NEC) and various electrical guidelines suggest that the appropriate wire gauge would typically be 6 AWG copper wire. This size is adequate to carry the required current safely without overheating or causing voltage drop issues, ensuring the system operates efficiently. In contrast, smaller gauges like 8 AWG, 10 AWG, or 12 AWG do not provide sufficient carrying capacity for a 40-amp breaker, which could lead to overheating and potential fire hazards. Therefore, understanding the ampacity of different wire sizes is vital for properly sizing the wire to match the circuit requirements and ensure safety in electrical installations.