Journeyman Electrician Practice Exam

In a junction box with a volume of 27 cubic inches and six size 12 AWG wires, what is the maximum number of size 10 AWG conductors that can be added?

1. 3

2. 4

3. 5

4. 6

The correct answer is: 5

To determine the maximum number of size 10 AWG conductors that can be added to a junction box with a volume of 27 cubic inches, we first need to consider the box fill calculations based on the National Electrical Code (NEC) guidelines. In electrical installations, each conductor occupies a certain volume in the box. For size 12 AWG conductors, each one counts as 2 cubic inches. Since there are six size 12 AWG wires in the junction box, they will occupy a total of 12 cubic inches (6 conductors x 2 cubic inches each). Next, we need to evaluate how much volume is still available in the junction box after accounting for the existing wires. The junction box has a total volume of 27 cubic inches, and with 12 cubic inches already occupied by the size 12 AWG conductors, there are 15 cubic inches remaining for additional wires (27 cubic inches - 12 cubic inches). Size 10 AWG conductors occupy a larger volume; each one counts as 2.25 cubic inches according to the NEC. To determine how many size 10 conductors can fit in the remaining space, we divide the available volume by the volume occupied by each size 10