Transformer is static device. two or more stationary electrical circuit mutually linked by magnetic circuit. assumptions of ideal transformer: 1. there are no losses. 2. whole magnetic flux constant no leakage. 3. permeability of core is infinite.
Step up transformer increases voltage level (decreases secondary current). Step down transformer decreases voltage level (increases secondary current).
In normal operation of transformer power, flux and frequency remain same (or almost same) at input and output.
EXAMIANS