Electrical Safety

The information given here is mainly in relation to the UK.

Electricity for Beginners or Underpinning Knowledge
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I like to explain about things by using analogies with everyday events that people can relate to. Electricity is no exception to the rule. Below you will find I use this technique where required.

Conductor
No not the person taking money on the bus. Any material that allows electricity to easily flow through it is said to be a good conductor. Copper iron, in fact most metals are good conductors. Wet paper, wet wood, wet soil etc. will all conduct electricity. Wet skin does also conduct electricity, since humans have sweat glands we are always wet. If we did not sweat then lie detectors would not work, because we produce more sweat when lying than not.

Insulators
In an electrical sense an insulator is a material that normally resists the flow of electricity through it. mica, Dry air, dry wood, dry paper, dry skin pure water, some plastic materials, glass etc.

The Electrical Circuit

For the majority of people we start the day at home full of energy, travel along roads to work and use some of the energy, come back home again using the other side of the road usually to be recharged again. Electricity is the same. Our home is to  electricity the source which could be a battery or the power station. The roads are the wires needed one going and one coming back. Work is the same for electricity it maybe to light a lamp or cook a Sunday roast. If overnight some one pulled up the roads or bricked up our doors and windows we could no longer get to work because our circuit was broken. This is the same for electricity. Unplugging the mains or operating a switch.

Voltage Current and Resistance

Imagine a large gate that is kept shut by a strong spring. One person pushing on the gate cannot open it at all. Another person comes along and with the combined pressure overcomes the springs resistance sufficient to allow one of the people to flow through. The more people pushing at the gate the greater is the pressure to overcome the resistance of the spring and hence more people can flow through.
In Electricity the pressure is called the voltage, flow is called the current and resistance is called resistance. Hope that helps with those terms. If not email me and let me know why not.

Alternating and Direct Current

This time we are going to prune some trees to explain these terms. The two pruning tools we are going to use are a chain saw and a hedge trimmer. Both achieve the same results but work differently.
To explain direct current take the action of the chain saw, the chain moves in the same direction and cuts the wood. Direct current is the same in that it too flows in the same direction.
The hedge trimmer moves backwards and forwards or oscillates and cuts the wood when moving in both directions. Alternating current is the same in that it flows first one way and then the other. The speed in which it changes direction per second or oscillates is called the frequency and is given the unit name of Hertz. In the UK the voltages changes direction 50 times in a second hence we have 50 Hz.

Why does electricity kill (Skip this bit?)

The brain sends tiny electrical signals to muscles in the body via nerves. Since the human heart is operated by muscles it needs the brain to send the electrical signals to keep it operating. Any interference to these signals will cause the heart to work incorrectly.  A flow of electricity from an external source through the human body can, if of sufficient magnitude interfere with the signals in the nerves. In order to get sufficient current flow the voltage must be high enough to overcome the bodies resistance. The lowest voltage that caused death by electrocution was around 60 volts if my memory serves me correctly and was an elderly lady in the United States of America. Now we in the UK have a domestic mains supply having a voltage four times that, namely 240 volts.

 So why can birds sit on cables which are carrying 12000 volts and not be killed? The birds are not forming a part of an electrical circuit (see above).
So how come we can be killed by touching a mains conductor (wire)?  For safety reasons one side of our mains supply is earthed. Earthing is carried out by having metal rods or pipes pushed into the ground connected to what is known as the neutral point at your local sub station. (further explanations would be too in depth to go into here as to why we need a neutral connected to earth or in deed, what is a neutral point?). Back to the question, the earth is thus one part of the electrical circuit and the wire is the other, that means that our bodies will complete the electrical circuit.