Question
Physics Question on Newtons Laws of Motion
A transformer is used to light a 100W and 110V lamp from 220V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately:
A
(A) 50%
B
(B) 90%
C
(C) 10%
D
(D) 30%
Answer
(B) 90%
Explanation
Solution
Explanation:
Given,Output power P=100WVoltage across primary Vp=220VCurrent in the primary Ip=0.5AEfficiency of a transformerη= output power input power ×100=PVpIp×100=100220×0.5×100=90%Hence, the correct option is (B).