A transformer transforms voltage and current. But the total electrical input and total energy output is almost same. Some losses are there ( core loss, iron loss etc).
We know that the power is the product of voltage and current(p=v*i).
The relation between primary voltage and secondary voltage is
An actual/theoretical transformer has no loss. But in practical there are several types of losses in transformer. In this page I am dealing with practical transformer making, so we will neglect the loss or take the loss as a predefined constant value.
Basic construction of transformer-
General transformers are mainly of two types.
the core of the transformer is mainly made from E and I shape iron plates