SIMPLE ELECTRIC CIRCUIT
• The two terminals of the electric cell are connected to two terminals of the bulb. Such an arrangement is an example of an electric circuit.
• In an electric circuit, the direction of current is taken to be from the positive to the negative terminal of the electric cell
• 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.
• If the bulb is not glowing even if it is connected to the cell that means the bulb may be fused.
An electric bulb may fuse due to many reasons:
• One reason for a bulb to fuse is a break in its filament.
• A break in the filament of an electric bulb means a break in the path of the current between the terminals of the electric cell.
• Therefore, a fused bulb does not light up as no current passes through its filament.
• The two terminals of the electric cell should not be joined without connecting them through a switch and a device like a bulb otherwise chemicals in the electric cell get used up very fast and the cell stops working.
An electric torch:
• An electric torch consists of a plastic casing, a bulb, electric cells, a slide switch and a reflector.
• The circuit is completed by putting two electric cells or batteries in the plastic case.
• When the switch is closed the circuit will be complete and the bulb will glow.
• The reflector will pass the light to a long distance.
• A switch is a simple device that either breaks the circuit or completes it. The switches used in lighting of electric bulbs and other devices in homes work on the same principle although their designs are more complex.
• When the switch is opened the flow of electric current stops
• When the switch is closed the flow of electric current starts.
It is represented by the symbol
• when it is 'ON' (closed circuit)
• when it is 'OFF' (open circuit)
Conductors and Insulators:
• Materials which allow electric current to pass through them are conductors of electricity.
• All metals like copper, silver gold even mercury which is in liquid form are conductors. Graphite; although a non-metal is a good conductor.
• Insulators do not allow electric current to pass through them.
• Examples of insulators include glass and wood. Also pure water and air are insulators. But some small impurities in water make it a good conductor. Our body which is 70% water is a conductor.
• Conductors and insulators are equally important for us. Switches, electrical plugs and sockets are made of conductors.
• Rubber and plastics are used for covering electrical wires, plug tops, switches and other parts of electrical appliances, which people might touch.
Precautions in handling electricity and electric devices:
• Electricity makes our lives comfortable, only if we take proper precaution and care.
• Carelessness in handling electricity and electric devices can cause severe injuries and sometimes even death.
We should use the Electric wires with proper insulation.
We should not poke finger or and other object into the holes of a plug point.
We should not plug in or take out the cords of electrical appliances with wet hands.
In case of fire due to short circuit, main power supply should be immediately cut off.
We should not connect too many appliances to a single socket.
We should not stick a metal object into any electrical appliance (toaster, cooler, AC, room heater, etc)
We should not touch a hanging wire on the road. It could be carrying current.