No load Transformer means a transformer which has no load connection at secondary winding only normal voltage is applied at the primary winding.
Let V_{1 } is applied at the primary winding. After applying A.C voltage V_{1}, it is seen that small amount of current I_{0 }flows through the primary winding.
In case of Ideal Transformer, no load primary current (I_{0}) will be equal to magnetizing current (I_{µ}) of the transformer. We assumed there is no core losses and copper loss, So I_{0 }=I_{µ} .
But, in case of actual transformer, there is two losses, i.e i) Iron Losses in the core i.e hysteresis loss and eddy current loss , ii) and a very small amount copper loss in the primary winding.

So, the primary current I_{0} has two components:

- I
_{w}= Iron loss component which is same ph of applied voltage V_{1}. - I
_{µ }= magnetizing component which is 90⁰ behind V_{1}.

Hench, the primary current I_{0 }is vector summation of I_{µ} & I_{w} ,
So, we can write that **I _{0 }= (I**