Electrician's Licensing Practice Exam

Which factor determines the size of the ground wire used on a service?

1. The length of the wire

2. The size of the largest conductor

3. The voltage of the system

4. The type of installation

The correct answer is: The size of the largest conductor

The size of the ground wire used on a service is determined primarily by the size of the largest conductor within the service. This is crucial because the ground wire's primary purpose is to provide a path for fault current to safely return to the ground in the event of a fault condition. Using a grounding conductor that is adequately sized to match or be proportional to the service conductors ensures that it can handle potential fault currents without overheating or breaking. The National Electrical Code (NEC) provides guidelines that establish the minimum size for ground conductors based on the ampacity of the service conductors. This approach helps maintain the safety and effectiveness of the grounding system, ensuring that it can perform its function under fault conditions. Proper sizing of the ground wire is vital to protect both equipment and human life from electrical faults.