Question

If $25\,W$ of power are applied to the primary of an ideal transformer with a turns ratio of 10, the power delivered to the secondary load is
A) $25\,W$
B) $0\,W$
C) $250\,W$
D) $2.5\,W$

Answer 1

Hint
A transformer changes either the potential or the current in the secondary load. In an ideal transformer, there are no energy losses associated with the transfer of power from the primary to the secondary load. So the power will remain the same.

Complete step by step answer
Transformers are electrical devices consisting of two or more coils of wire designed to transfer electricity by means of a changing magnetic flux. Transformers are capable of either increasing or decreasing the voltage and current levels of the primary supply to the secondary supply, without modifying its frequency, or the quantity of electric power being transferred from one winding to another via the magnetic circuit.
However, in a real transformer, there are various losses associated with the transfer of power from the primary to the secondary loads such as iron loss, hysteresis losses, etc. Such losses decrease the power transferred to the secondary load from the primary load.
However, we’ve been told that our transformer is ideal in nature and hence there are no power losses in our transformer. As a result, all the power applied to the primary coil will be transferred to the secondary load. Thus, the power delivered to the secondary load will also be $25\,W$.

Note
The number of turns in question will decide the ratio of the output to the input voltage or current depending on the type of transformer. However, since the power transferred is the product of the voltage and current, the net power transfer will be $25\,W$ for an ideal transformer so the number of turns is inconsequential to measure the power delivered to the second load.