Diesel Generator

Diesel Generator and electricity, A  The pipe attached to the tank represents the resistance. It is very similar to an electrical resistance. For example, if we double the length of the pipe, the flow of water will decrease to about half its previous value. There's twice as much pipe, therefore twice as much resistance. If we make the pipe thinner, this will also slow down the flow.

This is true of electrical cables as well. A longer cable has more resistance than a shorter one, and a thin cable has more resistance than a fat one (but of course it is the thickness of copper that is important, not the thickness of the insulating plastic). Cable sizes are expressed in terms of the cross-section area of copper in the live and neutral conductors, measured in square millimetres (abbreviated to `mm<sup>2</sup>' or `sq mm'). Electrical power rings are very commonly made from 2.5 mm² cable. This means that each of the live and neutral conductors has an area of 2.5 mm². You'll frequently hear this abbreviated to `2.5 millimetre' or `2.5 mil'.

Strictly speaking, this is wrong: the conductors are not 2.5 millimetres across, they have an area of 2.5 square millimetres. This slang does not normally cause problems in practice.n electrical current is the flow of electricity around an electrical circuit.

The flow of electricity follows similar principles to the flow of water in pipes, as we shall see, with the exception that an electrical system must make a complete circuit. The circuit will contain a power source of some kind; in mains wiring the power source is the national electrical distribution system which is mostly outside our control. Of course, the distribution company don't run wires directly from the power station to our houses: there is all manner of other stuff between them and us, but that isn't all that important. For most cases you can proceed as if a small power station was connected directly to your house.

  In domestic electrical work, current is generally measured in amps. Currents you will encounter in practice range from about 0.5 amps (through a lightbulb) to about 40 amps (an electric shower). Technically `amps' is short for `Ampиres', but the full name is now rarely used. The mathematical symbol for current, as it is written in calculations, is not `C' (for current) or `A' (for amps) but in fact `I'. This is just because the symbols `C' and `A' are reserved for other things. You will occasionally come across currents measured in milliamps (`mA' for short). A milliamp is a thousandth of an amp. For example, most earth-leakage breakers used in domestic wiring trip at 30 mA, which is about one thirtieth of an amp.