How does a plug work?

[roomby]

Can anyone explain in simple terms how an electrical plug works? e.g power comes in to the plug through the live wire but what does the neutral wire do? what does the earth do? how does the fuse work? Does power ever flow back along the neutral wire, or is it all used by the appliance? Does the appliance 'draw' the power it needs or is there a constant flow? Thanks.

[sddsddean]

OK, lets start simple. Imagine you have a 1.5V battery with a bit of wire from the positive end going to one terminal of a bulb and a bit of wire going from the other terminal of the bulb to the negative end of the battery. Hey presto, we have an electric circuit and the bulb lights up. Keeping it simple, electricity flows from the positive end of the battery(the live wire), through the filament of the bulb, and back to the bulb(along the neutral wire). (Strictly speaking, it doesn't quite work like this, but I'm keeping it simple). By extension, imagine the battery is the national grid and the bulb is your appliance. A plug is just a way of connecting the live and neutral wires to the 'power station' to make the elecric circuit. The Earth wire is a safety device. It is connected to all the metal bits of your appliance, so that should a wire fail or 'short circuit' in the appliance, the electricity will go safely to earth and not through you giving you an electric shock. Earth wires are usually connected to water pipes in a domestic situation, as they run through the earth. A fuse is essentially a very thin bit of wire that will burn through if it gets overloaded (normally due to short circuits). It burns and breaks, breaking the elecric circuit and switching the appliance off. This is because if the appliance kept drawing too much electricity, the flex would overheat and catch fire. So a fuse actually stops the flex catching fire. An appliance will draw the power it needs. If you have a 3 bar fire and only have 1 bar on, it only needs a 1/3 of the power it would need with all 3 bars on. Hope this helps.

[tortolano]

Im puzzled ,because in my house, at the main switch, the earth wire that is connected to all my sockets etc, isnt connected to no waterpipes or earth rod but is strapped directly onto the main neutral connection. Surely this makes them one and the same. (rewired under 6 years ago by NORWEB)

[lisaj]

funny, I thought electons flowed from negative to positive... what with their negative charge and all :-)

[gmc2002]

Electron flow is as you describe lisaj, the current flow described by sddsddean is often called "conventional current"; i.e. it is a convention that current is described this way despite the direction of electron flow. here is a paper for more details http://www.iop.org/EJ/S/3/30/.iDJdIyA8Ahp2CsjZbN9v
A/article/0031-9120/9/2/115/pev9i2p111A.pdf