How many current-carrying conductors are needed between two three-way switches?

• A. 3
• B. 2
• C. 4
• D. 5

Answer: (A)

The essential idea is that a 3-way switch circuit between the two switches uses three conductors that carry current in normal operation. Two of them are traveler conductors, which shuttle the switching signal between the switches. The third conductor is the common, which carries the actual current path—either the hot feed to the second switch or the switched hot to the load—depending on how the box is wired. The grounding conductor isn’t part of that current path, and the neutral typically isn’t run between the two switches in this setup. So three current-carrying conductors are needed between the switches to make the circuit work in both switch positions.