hgh

A magnetic field is generated around the primary solenoid
when an electric current is passed through it by
connecting the ends of the solenoid to a battery cell. But
induced emf is not produced in the secondary solenoid as
there is no change in this magnetic flux. When the switch
is on and off the flux linked with the secondary coil
changes and thus an emf is induced in the secondary coil.
x Here AC is passed through the primary coil. The direction
of ac changes at regular interval continuously. As the
secondary coil is located at this magnetic field which
changes at regular interval continuously, the change in
flux causes the production of an induced emf in the
secondary coil continuously. So the bulb glows
continuously. If the number of turns of the secondary is
more than the number of turns of the primary the induced
emf increases and if the number of turns of the secondary
is less than the number of turns of the primary the
induced emf decreases.
x When there are two nearby coils the variation of current
in one of them produces a change in the magnetic flux
around it and an emf is induced in the secondary coil.
Transformer: Transformer are Two types
Step up transformer
x Increases AC voltage
x Number of turns is less and thick wire is used in primary