A
transformer has maximum efficiency at full load. When iron losses are 800
watts, copper losses at half load will be
1600 W
800
W
400 W
200
W
200
W
Given
:Iron loss (Pi) = 800W
As
we know that for maximum efficiency 
, we have
At
half load, when 
, we have copper loss that will be
Hence,
the correct option is (D).
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