# Transformers

### Explanation of question 3

A 1:10 step-up transformer supplies a secondary load of 600 resistance. If the primary voltage is 12V, the primary current will be

1. 0.02A
2. 0.2A
3. 2A
4. 20A

The answer is :- 3

Remember power is the same on both sides of the transformer - if the voltage is stepped up by a factor of 10, then the current must be stepped down by the same degree, a factor of 10.

If primary voltage is 12V then the secondary voltage will be 120V. By Ohm's law, secondary current = 120/600 = 0.2A. Therefore the primary current will be 10 times this value, i.e. 2A

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