What is a Switch in an Electrical Circuit
Electric switch
We use electric switches to put on or off the electrical devices and machines. But do you know how it works?
An electric switch is a device that is used to open or close an electric circuit. When we open an electric circuit, the flow of electric current in the circuit stops, and when we close an electric circuit, an electric current flows through it. In an electrical circuit, a switch is sometimes referred to as a ‘key’.
A fuse, short for fusible link, is a safety device that prevents a large amount of current from flowing into a device or appliance. It consists of metal wire that melts easily when heated.
The key is represented by the symbol
Activity
Aim: To make an electric switch (adult supervision required)
Materials needed: Three pieces of wire about 10 cm each, a safety pin, two board pins, a piece of cardboard, a pencil cell, a sharp blade, and a small torch bulb
Method:
1. Take the piece of cardboard and place the safety pin on it.
2. Strip the ends of the three pieces of wire so that about 1 cm of the metal wire is exposed.
3. Attach a piece of wire to a drawing pin. Push the drawing pin through the end loop of the safety pin into the cardboard.
4. Attach the second piece of wire to the second drawing pin. Push the drawing pin into the cardboard, about 1 cm away from the first drawing pin. Make sure that the safety pin held in place by one drawing pin can be turned to touch the other pin. Now your switch is ready.
5. Do you want to test the switch? Connect the free end of one of the wires to one terminal of the pencil cell. Connect the third wire to the other terminal of cell and to the bulb.
6. Connect the free wire from the switch to the other side of the bulb.
7. Turn the safety pin such that it touches both the drawing pins.
Observation: The bulb glows when the safety pin is turned such that it touches both the drawing pins.
Electric torch
A schematic diagram of an electric torch is shown in Fig. 14.10. An electric torch has one or more dry cells inside it, which act as the ‘source’. These cells are connected through a switch to a small bulb. When the switch is pushed to the ‘on’ position, the circuit is complete and the bulb glows. When the switch is pushed to the ‘off’ position, the circuit is incomplete (broken). Now the current cannot flow through the circuit, and the light goes out.
