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Safety and Electricity

Safety and Electricity



Many of the electrical appliances in our homes plug into sockets connected into the main supply.Mains electricity is produced at power stations by the electricity generating board.It is then sent along power lines to houses,factories,hospitals,schools and other users.The electricity board supplies two wires to your homes .One is called live while other is called neutral.The live wire is at about 230 volt the neutral wire is at about 0.Electrical circuits  at your home are connected to these wires.There are two main differences between the using the mains as a supply and using a battery.

(1) This type of cell or battery used in a torch gives a voltage of about 1.5 volt.Main electricity is at about 230 volt.The main can supply very large currents.It is dangerous to wires connected to the main supply.An electric shock could kill you.

(2) A battery gives you a steady voltage so ,when it connected in a circuit,the electricity always flows in the same direction.This is called direct current or DC.The main voltage changes direction very rapidly .This makes the current flow backwards and forwards 50 times in each second.We say that this is an current or AC with a frequency of 50 HZ.

Main electricity makes our lives more  comfortable but it can be dangerous if not handled correctly.To prevent damage to property and danger to life ,household circuits have built in safety measures.

Fuses :

A fuse contains a thin piece of wire which will melt if the current gets too high and leaves a gap in the circuit.This stops the current ,preventing the over heating of the electrical circuit which may cause a fire.Fuses are put in the live wire close to the electricity meter in a box called the consumer unit.When a fuse in the consumer unit blows,it must be replaced with one of the correct size.It is very dangerous to use ant thing other than the correct fuse.

Circuit Breaker :

Some consumers units have miniature circuit breaker (mcbs) in them instead of fuses.A circuit breaker is an automatic switch which turns off the current if it gets too high .Unlike a fuse ,a circuit breaker can be resat.For extra safety ,when using extension cable to potentially dangerous appliances such as electric saws and drills, a residual current circuit breaker (rccb) should be used.

Choosing The Correct Fuse:

The main fuse in the consumer unit protect the house circuits from damage due to too much current.However each appliance can also be protected by a fuse in its plug.If the current gets too great ,the fuse wire melts and breaks the circuit.When this happens we say that the fuse has blown.Fuse can be bought which blow at different currents.The fuse used in plug should have a current rating just big enough to let the appliance work properly.If it is rated too high a current it could allow an over load to cause damage without melting and blowing.Fuses are made in various values --1A--2A--3A--.Household appliance fuses are usually chosen from the following values .3A-5A-13A.

Calculating Currents : 

Electrical appliances are usually marked with their power rating which shows how much electrical energy they convert in each second.Electrical power is measured in watts and kilo watts.It can be calculated by the following formula
Electrical power = voltage multiply by Current.    










     
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