Question

The diagram below shows a bulb connected by dual control switches. Observe the diagrams and answer the questions that follow.

1. Which of the above circuits will be able to switch ON or switch OFF the bulb using both switches?
2. At present, in which circuit is the bulb glowing?
3. If we interchange the L and N wires in circuit B, will the circuit work?

Answer 1

1. Both circuits A and B are correct two-way switch connections. In both, operating either switch changes the state of the bulb, so the bulb can be switched ON/OFF from both ends.
2. As shown, the bulb is glowing in circuit A because the straight connections complete the circuit for the switch positions shown; in circuit B those switch positions leave the circuit open.
3. Yes, the bulb will still glow because the bulb does not depend on which supply wire is live or neutral. However, interchanging L and N would put the switches on the neutral side, which is unsafe. L and N should not be interchanged in household wiring.