Draw a circuit diagram using the dual control switches to light a staircase electric light and explain it's working.

Below circuit diagram shows the use of dual control switches to light a staircase electric light:

Two switches S₁ and S₂ are used. The switch S₁ is fitted at the bottom and the switch S₂ at the top of the staircase. Figure (a) shows the off position of the bulb.

The bulb can now be switched 'on' independently by either the switch S₁ or the switch S₂. If the switch S₁ is operated, the connection 'ba' is changed to 'bc', which completes the circuit and the bulb lights up [figure. (b)]

Similarly, on operating the switch S₂ from the position shown in figure (a), the connection 'bc' changes to 'ba' which again completes the circuit figure (c) and the bulb lights up.

Similarly, if the bulb is in 'on' position as shown in figure.(b) one can switch 'off' the bulb by changing the connections 'bc' to 'ba' either by operating the switch S₁ or the switch S₂. But, if the bulb is in 'on' position as shown in figure (c), it can be switched 'off' by changing the connections 'ba' to 'bc' either by the switch S₁ or by the switch S₂.