Question

If N1 and N2 are numbers of primary and secondary coils of a step up transformer , then

Answer 1

On a step up transformer there are more turns on the secondary coil than the primary coil. the induced voltage across the primary coil or in other words the voltage has been "stepped up".

Explanation:

A step up transformer is one whose secondary voltage is greater than its primary voltage. this kind of transformer steps up the voltage applied to it.

The number of turns on the secondary side of the transformer is greater than that of the primary, i.e. $N_{2}>N_{1}$. thus the voltage turn ratio of step up transformer is 1:2