Working Principle of Transformer

An elementary transformer consists of soft iron core and two windings placed on it. The core is built up of thin soft iron or silicon steel laminations to provide low reluctance to the magnetic flux.

Working:

When the primary winding is connected to an ac supply mains, a current flows through it. Since, the winding links with an iron core, so current flowing through this winding produces as alternating flux in the core. This alternating flux links with the secondary winding. Due to Electromagnetic Induction, emf gets induced in the secondary winding.
The induced emf in the secondary winding enables it to deliver current to an external load connected across it.
Thus, energy is transferred from primary to secondary winding by means of Electomagnetic induction without any change in frequency.

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