NCERT Solutions Curiosity Chapter 3 Activity 3.9: Let us test — Electric switch
Book page 32 Updated on2026-09-05
Q1.
Connect the electric cell, lamp, and switch as shown in Fig. 3.12a. Does the lamp glow?
Answer
No, the lamp does not glow.
In Fig. 3.12a the free end of the safety pin is turned away, so it does not touch the second drawing pin. There is a gap between the two drawing pins, and air fills that gap.
Gap between the drawing pins → circuit open → no current → lamp dark
This is the OFF position of the switch, and we say the circuit is open.
Q2.
Rotate the free end of the safety pin till it touches the other drawing pin as shown in Fig. 3.12b. Does the lamp glow now?
Answer
Yes, now the lamp glows.
The safety pin is made of metal, a good conductor. When its free end touches the second drawing pin, it closes the gap and completes the path.
Safety pin touches both drawing pins → circuit closed
Current flows from the cell's + terminal → through the lamp → back to the – terminal Lamp glows (ON position)
Why it happens: The cardboard the pins are fixed to is an insulator, so the current cannot cross from one pin to the other through the board. Only the metal safety pin can carry it across. That is the whole idea of a switch — a movable conductor over a fixed gap.