Transformer on DC :
Transformer cannot work on DC.
Transformer works on electromagnetic induction principle.
Electromagnetic induction principle means when flux linking with coil changes and EMF induced in it.
Suppose we give DC to a transformer then DC will set constant magnetic field in transformer Core.
Due to constant magnetic field there will be no induced EMF in primary winding of transformer. Since, there is no induced EMF in primary of transformer there will be no induced EMF in secondary of transformer. The electric power cannot be transferred. If the rated DC voltage is applied high current will be drawn in primary winding of transformer. Due to high current flow in primary winding of transformer more heat will be generated. Due to heat winding insulation will burn.