adoy said:
why does a core creates a power factor and how does it happend?
The core of the tx is made up of material having some hysteresis loss and eddy current loss.To supply these losses ,a working component of no load current.no load current has to supply magnetic current also to magnetise the core which is 90 degree out of phase with v(lagging ).This gives rise to no load power factor angle which is @ 70-80 degree.