basics of making transformer (part-1)

if you ask a child, what is transformer?  most of them will tell about the famous  Hollywood movie, but I think you are not like that. I think all the hobbyists must heard about the transformer.
what is a transformer?
A transformer is an electrical device,which transforms power magnetically with out changing total power and the supply frequency. it is mainly two types 1.step up (transforms lower voltage to a higher level) 2.step down(transforms higher voltage to lower voltage).
why we need a transformer?

the uses of transformer starts from power stations, from where power is transmitted to a longer distance, the extension line has to provide a large amount of power through it, we know that power=voltage*current, and loss is directly proportional to the square of current. as the current through the extension increases the loss also increases,  so for transmitting a fixed amount of power we can make the current less and the voltage higher one to minimise the loss, 
so making this voltage several kilo volt, we need a transformer.
after transmission, at the distribution station we need to make the voltage lower value for household or industrial using,
actually, transformer is everywhere, in every electronic or electrical good.

How a transformer works?
A transformer works according to the principle of mutual inductance,
suppose you have an inductor, and give a ac supply to this inductor,  the there will induce a changing magnetic flux in the coil. if you place another coil near it a counter emf will be generated in that coil. here is air between two coil, for transformer there will be a iron core.

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