A transformer is used to light 100 W – 110 V lamp from 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is
96%
90 %
99 %
95 %
η=PoutputPinput=100220×12=100110=1011≈90%
A transformer ia used to light a 100W and 110V lamp from a 220V mains. If the main current is 0.5amp ,the efficiency of the transformer is approx
1)10%
2)30%
3)50%
4)90%