State the principle of working of a transformer.
(b) Define efficiency of a transformer.
(c ) State any two factors that reduce the efficiency of a transformer.
(d) Calculate the current drawn by the primary of a `90%` efficient transformer which steps down 220 V to 22 V , if the output resistance is 440 `Omega`.

Explanation

### Step-by-Step Solution

**(a) Principle of Working of a Transformer:**
A transformer operates on the principle of mutual induction. It consists of two coils, the primary coil and the secondary coil, wound around a magnetic core. When an alternating current flows through the primary coil, it creates a changing magnetic field. This changing magnetic field induces an electromotive force (EMF) in the secondary coil, allowing electrical energy to be transferred from the primary to the secondary coil.

**(b) Efficiency of a Transformer:**
The efficiency (η) of a transformer is defined as the ratio of the power output to the power input. It can be mathematically expressed as:
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