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

• A. 2
• B. 4
• C. 3
• D. 5

Answer: (C)

The key idea is how many conductors actually carry current in the segment of cable between the two switches in a typical three‑way circuit. In a common setup, the run between the switches is a three‑conductor cable. Two of those conductors act as travelers between the switches, and the third conductor completes the circuit from one switch to the other (carrying current as the switching state changes). Because all three insulated conductors in that section can carry current, there are three current-carrying conductors sealed between the two switches. Neutrals don’t pass through the switches and thus aren’t counted in that segment, and the ground conductor isn’t counted toward current-carrying conductors for box fill.