Basic electricity

Electricity produces three effects:
1. heat and light as in a light bulb, electric fire or cooker;
2. magnetism as in an electromagnet;
3. chemical changes as in electrolysis and electroplating.

Conductors and insulators

A material which will allow electricity to flow through it is called a CONDUCTOR and one which will not is called an INSULATOR.
All metals are conductors, as are many liquids. Insulators are materials like plastics and rubber.

Voltage and current

In Britain the mains voltage is 240 V; the current taken from a socket depends on what you are using. Most plugs now have a 13 A fuse but this maybe too large for some things and you should always check.

The plug

There are three wires to a modern 13 A plug:
1. live - coloured brown
2. neutral - coloured blue
3. earth - coloured green/yellow stripes.

Earth

The earth wire is there to prevent the casing of the equipment becoming live if something goes wrong. The electricity is conducted to earth, usually via a metal water pipe.
Some things only have two wires with no earth, they have plastic cases or cases made of other non-conducting material.

NEVER ALTER ELECTRICAL CIRCUITS AT HOME IF THEY ARE PART OF THE MAINS.

Light bulbs

The filament in a light bulb is a coiled coil of tungsten wire. The inside of the bulb is filled with argon or nitrogen and not air. The wire glows white hot when a current flows through it. It does not catch fire because of the lack of oxygen.

Switches

The purpose of a switch is fairly obvious component but they too must be correctly connected. You must always connect a switch in the live wire so that the socket/appliance is not live when it is switched off.

Fuses

A fuse is usually a thin piece of wire that will melt and break the circuit if too large a current flows through it. The thicker the wire the more current is needed to melt it and the higher the 'rating' of the fuse. The purpose of a fuse is to protect the wiring and the equipment. If the fuse was not there and something went wrong then the wires themselves would get hot and maybe catch fire. In a plug the fuse is in a glass tube.

Fuses should also be connected in the live wire you should always switch off before changing a fuse.
The normal fuse ratings are 13 A, 5 A, 3 A and 1 A. Currents bigger than these will 'blow' the fuse.

Circuit breakers

In houses today most fuse boxes are being replaced by a set of switches called circuit breakers. These act a bit like a fuse, cutting off the supply if there is a problem. However they are based on an electronic circuit and are safer than fuses because they act to cut off the current much more quickly.

Direct current (d.c) and Alternating current (a.c)

There are two 'types 'of electricity depending on how they were produced.

Direct current - or d.c. This means current that is always flowing in the same direction, and is taken to be from positive to negative; d.c. is made by a battery or a d.c. generator.

Alternating current - or a.c. This means current that is constantly changing direction, first flowing one way and then the other. In Britain a complete cycle takes one fiftieth of a second - the frequency of the mains is 50 Hz.

You can see how the voltage of d.c. and a.c. changes with time if you connect them to an oscilloscope.