# Homework Help: Voltages and Turns in a Transformer

1. Jul 24, 2011

### fromthepast

In a step-up transformer, should the ratio of the voltages be approximately equal to the ratio of the number of turns? Why?

Same for a step-down transformer: should the ratio of the voltages be approximately equal to the ratio of the number of turns? Why?

Thanks

2. Jul 24, 2011

### rock.freak667

For starters how does Faraday's law apply to the transformer in either the primary or secondary side?

3. Jul 24, 2011

### fromthepast

Faraday's law includes the rate of change in magnetic flux through the coil and the number of turns in the coil. I think that the ratio of the secondary emf over the primary emf should equal the ratio of the secondary turns divided by the primary turns; so they should be equal for step-up and step-down. Is my thinking right?

4. Jul 24, 2011

### rock.freak667

Yes they will be the same for any transformer (ideal).

For a step up transformer, the number of turns in the secondary > number of turns in primary so the voltages will change accordingly but the ratios of Ns/Np will remain the same.