It is a device which works on AC. It is used to increase as decrease the magnitude of alternate voltage as alternating current.

Principle :-

It is based upon the principle of mutual induction.

Construction :-

It consist of two coils primary and secondary wounds on a common laminated core made up of soft iron. Two coils are formed by different type of wire and their no of turns may also be different

Let Np and Ns be the total no. of turns in primary and secondary reap.

Theory and working :-

AC source is connected across primary varying current flow through primary which various magnitude as well as direction hence produces varying magnetic flux. This varying flux passes through secondary through the core hence EMF is induced in it. If flux through primary is grooving then it will also grow through secondary. In other wards flux charges in a similar manners in both the coils but due difference in the total no. of turns the EMF in two coils are different.

According to the law of electromagnetic induction EMF’s is primary and secondary are give 

E  x  N= constant

Transformers is highly efficient device :

Input and output powers are almost equal. If Ip and Is are currents in primary and secondary we have

E_p I_p = E_s I_s

Transformer is of two types :

1. Step up transformer
2. Step down transformer

1. For step up transformer      E_s > E_p .   also    N_s > N_p   and        I_s  <  I_p
2. For step up transformer      E_s < E_p .   also    N_s < N_p   and        I_s  >  I_p

    

   Transformation ratio (K)

   The ratio Ns/Np is known as transformation ratio

   For step up transformer   K>1

   For step down transformer   K<1

   Applications :-

3. Voltage stabilizers
4. UPS
5. Inverter
6. AC Adapters
7. Charges
8. CVT ( Count and voltage transformers)
9. Welding set
10. Battery eliminator or power supply
11. Long distance transmission of electrical power.   
12.