# Transformers

### Explanation of question 5

In Fig. 11.1, the apparent resistance seen at the primary terminals is

1. 0.15
2. 0.39
3. 60
4. 1200

The answer is :- 4

The impedance ratio primary to secondary is the same as the square of the turns ratio. Thus, for a turns ratio of 20:1, the corresponding impedance ratio will be 400:1. Thus the primary impedance will be 400 times that of the secondary circuit, i.e. 1200

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