Science Projects Index

How to make an electrical switch?

Take a wooden plank and insert two drawing pins into it. Now make a complete circuit containing a bulb, a battery and wires. Cut one of the wires in the circuit and connect them to the two drawing pins, one on each. Unfold a paper clip and hook one end of it to one of the drawing pins and then bend its other end upward above the other drawing pin. Now you will see that whenever you press this end in such a way that it touches the drawing pin below it, the bulb gets lighted.

That is because each time it touches the pin, the circuit gets completed. When you leave the clip and it moves up away from the pin, the light goes off, as the circuit is broken. So this paper clip acts as an electrical switch.

Building a Circuit

Get a pencil torch bulb and its holder. Connect two pieces of wires to the terminals of the holder. Insert the bulb in the holder. Connect the other ends of the wires to the terminals of a pencil torch battery. As the connection is completed, the bulb will be seen to light up. Now the circuit is complete.