Q.What is a transformer? Explain construction and working of a transformer. Derive the equation for a transformer.

Transformer: mutual induction between two windings on a common core changes AC voltage.

Transformer: a static device that changes an alternating voltage from one value to another (step-up or step-down) using the principle of mutual electromagnetic induction, without changing the frequency.

Construction: two separate coils of insulated copper wire — the primary ($N_p$ turns) and secondary ($N_s$ turns) — are wound on a common laminated soft-iron core (laminated to reduce eddy-current losses; soft iron for low hysteresis loss and high permeability, so nearly all flux links both coils).

Working: an alternating voltage $E_p$ applied to the primary drives an alternating current, which sets up an alternating magnetic flux $\phi$ in the core. This changing flux links the secondary winding too (ideally the same $\phi$ through every turn of both coils) and, by Faraday's law, induces an emf in it.

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