I agree the produce power will be loss, I ask how can?

Question

It’s gone out like Heat or what ?

Answer 1

Reword your question, this one makes no sense at all.

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Answer 2

Yes, generally the reason why the power out of a generator is less than that put in is due to heating effects.  Some of it is electrical I²R losses and some is mechanical heat due to friction.  There are other effects too, but these are the major ones.