Question

What will be the output if we apply a square wave signal in transformer input.

Answer 1

Well, as any square wave can't be ideal , it has to have some definite level of transition time, in this case the output will be spikes or impulse.
If ideal square wave is employed no output

Hope this helps

Answer 2

What will be the output if we apply a square wave signal in transformer input.

Answer: if we apply a square wave signal in transformer input we will probably get a filtered square wave that has lost its high frequencies. It will look rounded off and ripple in top. It will pass pulses in the same manner with some reduction of the higher frequencies.

I hope it helps, Regards.