What is step up transformer ? How it differs from step down transformer ?

Explanation

The ratio of number of turns in the secondary coil to the number of turns in the primary coil is called transformer ratio. `T = (N_(S))/(N_(P))=("No of turns in the secondary")/("No of turns in the primary")`
If `N_(S) gt N_(P)`, then the transformer is called step up transformer.
If `N_(S)lt N_(P)`, then the transformer is called step down transformer.