Electrical Properties
Conduct or insulate?
Some materials used in electrical appliances need to be good conductors of electricity. Other materials must be bad conductors (called insulators). These stop us getting a shock.
The pins in an electric plug are metal. Because they make the electrical connection they must be able to conduct electricity. The casing, however, is made of plastic, an insulator that stops you getting an electric shock when you plug into a live socket.
But things aren’t that simple. Not all conductors are as effective as one another. Not all insulators as effective as one another. And there is a third group of materials called semi-conductors.
Shocking haircut
A market stall in Ipswich was told to stop selling “potentially lethal” hair clippers by trading standards officials.
The clippers did not have any British Standard markings, and did not comply with safety regulations. Their plug pins did not have plastic sheathing, posing a serious risk of electrocution.
Blowing a fuse
Why do some electronic circuits need fans to cool them down? Well, when current flows in a metal wire, some of the electrical energy is changed to heat energy. The greater the electrical resistance of a material, the hotter it gets. If the metal parts of the circuit wires get too hot they could start to melt. Cooling fans cool the circuits and prevent this from happening.
Fuses are deliberate ‘weak’ points in an electric circuit. They protect other parts. When current flows through the fuse wire it gets hot. If too much current flows it melts, breaks and cuts the circuit. Your appliance is not damaged.
Fuses come in various standard ratings, based on the amount of current they can take before melting.