Chapter Notes and Summary
• things that causes bulb to glow is called electricity or electric current.
• electricity we get in our houses is generated in power stations.
• Power stations are generally located in remote areas.
• electricity generated is carried out to our homes through wires.
• In case of power cut, we use small generators to generate electricity.
• Electric cell is a source of electricity that converts chemical energy into electrical energy.
• Electric cell has two terminals i.e. positive and negative terminal. If two terminals of electric cell join directly, then chemicals in electric cell get used up very fast and cell stops working.
• A device which converts electrical energy into light and heat energy is called electric bulb.
• An electric bulb consists of a transparent glass covering. It encloses a thin, coiled metal wire known as filament.
• filament is made up of tungsten that is supported by two thick wires. One of these wires is connected to metal base of bulb and other wire is connected to tip at bottom.
• metal case and tip at bottom are two terminals of bulb. filament of bulb glows on passing electricity through it.
• electric switch slides between ON and OFF positions. bulb glows in ON position and stops glowing in OFF position.
• Wire is a link between bulb and switch.
• Spring is a link between cells and switch.
• suitable arrangement of cell, bulb, wire and switch, which provides a complete path to flow of electricity is called an electric circuit.
• bulb glows only when current flows through circuit.
• direction of current in an electric circuit is to be taken from positive to negative terminal of battery or cell.
• Closed circuit is circuit in which there is no break anywhere in circuit. Current flows easily in a closed circuit.
• If there is a break any where in circuit, electric current stops flowing. Such a circuit is called open circuit.
• Electric cell was first invented by Alessandro Volta, an Italian scientist.
• material that allows electric current to pass through it is called a conductor of electricity.
• material that does not allow electric current to pass through it is called insulator.
• Plastic is an insulator which prevents us from getting electric shock.
• bodies of electric switches, sockets, plugs and handle of an electric iron are made of insulating materials.
• Safety precautions while handling electrical gadgets are :
• Never touch any electrical device with wet hands.
• Always wear rubber-soled footwear during use of an electric device.
• Always use a fire extinguisher to douse electrical fire.
• Never play with electrical equipment.