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### Step up transformer:

If (N_{s }greater than N_{P) }and (V_{s }is greater V_{p}) such a transformer in which voltage across secondary is greater than the primary voltage is called a step up transformer.A step up transformer has more turns in its secondary winding than its primary winding and is used to increase the ac voltage.

The turns ratio for a step up transformer is always greater than 1 because the number of turns in the secondary winding is always greater than the number of turns in the primary winding.

### Step down transformer:

If (N_{s }is less then N_{P}) the number of turns in the secondary is less than the number in primary,and (V_{s }is less then V_{p}) ,such transformer in which voltage across secondary is less than the primary voltage is called a step down transformer.The turns ratio for a step down transformer is always less than 1 because the number of turns in the secondary winding is always fewer than the number of turns in the primary winding.