Electricity makes it possible to light our homes, roads, offices, markets and factories even after sunset.
A power station provides us with electricity.
Electricity to the bulb in a torch is provided by the electric cell.
Electric cells are also used in alarm clocks, wristwatches, transistor radios, cameras and many other devices.
All electric cells have two terminals; a positive terminal and a negative terminal.
Never join the two terminals of the electric cell without connecting them through a switch and a device like a bulb. If you do so, the chemicals in the electric cell get used up very fast and the cell stops working.
A torch bulb has an outer case of glass that is fixed on a metallic base.
The thin wire that gives off light is called the filament of the bulb.
The filament is fixed to two thicker wires, which also provide support to it. One of these thick wires is connected to the metal case at the base of the bulb. The other thick wire is connected to the metal tip at the centre of the base. The base of the bulb and the metal tip of the base are the two terminals of the bulb. These two terminals are fixed in such a way that they do not touch each other.
The electric circuit provides a complete path for electricity to pass (current to flow) between the two terminals of the electric cell.
The bulb glows only when current flows through the circuit.
In an electric circuit, the direction of current is taken to be from the positive to the negative terminal of the electric cell.
An electric bulb may fuse if its filament is broken.
A switch is a simple device that either breaks the circuit or completes it.
Materials which allow electric current to pass through them are conductors of electricity. Eg: Iron, Copper.
Insulators do not allow electric current to pass through them. Eg: Wood, Plastic.
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