Question

Connect a circuit on a wooden plank or on a thermocol sheet as shown in Figure. Insert two drawing pins at A and B. Insert a safety pin in between A and B. such that one end of the pin is completely in contact with B and the other end is left free. Now observe the bulb.

• What do you notice?
• What happens?
• Why doesn’t the bulb glow when the safety pin is left free at one end?

Answer 1

• The bulb does not glow. Now touch the safety pin to pin A and observe the bulb again. 
• The bulb glows.
• In this activity, the safety pin is used to close /open the circuit. When the safety pin is left free at one end, the circuit is open. So the bulb doesn’t glow.