Write the working procedure of transformer.

Explanation

When an alternating voltage is applied to the primary the resulting current produces an alternating magnetic flux which links the secondary and induces an emf in it.
The value of emf depends on the number of turns in the secondary.
Let an ideal tranformer in which the primary has negligible resistance and all the flux in the core links both primary and seconary windings.
If no any load joined to a secondary and `N_(p)` and `N_(s)` are the number of turns in primary and secondary respectively then induced emf in primary coil is,
`epsilon_(p) = - N_(p) ( d phi)/( dt)` ...(1)
and induced emf in secondary coil is,
`epsilon_(s) = - N_(s) (d phi )/( dt) ` ...(2)
but `epsilon_(p) = V_(p)` and `epsilon_(s) = V_(s)`
where `V_(p0` and `V_(s)` are voltage across primary and secondary coils respectively.
Equation (1) and (2) can be written as below,
`V_(p) = - N_(p) (dphi)/( dt) ` and `V_(s) \ = - N_(s) (dphi)/( dt)`
`:. (V_(s))/(V_(p)) = ( N_(s))/( N_(p))`
The above relation has been obtained using three assumptions.
(1) The primary resistance and current are small .
(2) The same flux links both the primary and secondary as very little flux escapes from the core and
(3) The secondary current is small.
The ratio of number of turns in secondary coil `N_(s)` to the number of turns in primary coil `N_(p)` is called transformation ratio `lamba`.
`:. lambda= ( N_(s))/( N_(p))`
If the secondary coil has a greater number of turns than the primary `( N_(s) gt N_(p))`, the voltage is stepped up. This type of arrangement is called a step up transformer.
If the secondary coil has less turns than the primary `N_(s) lt N_(p)` .In this case `V_(s) lt V_(p)` . This type of arrangement is called a step down transformers. The voltage is stepped down or reduced.