A) 30%
B) 50%
C) 90%
D) 10%
Correct Answer: C
Solution :
The efficiency of transformer \[\text{=}\frac{\text{Energy}\,\,\text{obtained}\,\,\text{the}\,\,\text{secondary}\,\,\text{coil}}{\text{Energy}\,\,\text{given}\,\,\text{to}\,\,\text{the}\,\,\text{primary}\,\,\text{coil}}\] or \[\text{=}\frac{\text{Output}\,\,\text{power}}{\text{Input}\,\,\text{power}}\] or \[\eta =\frac{{{V}_{s}}{{I}_{s}}}{{{V}_{p}}{{I}_{p}}}\] Given, \[{{V}_{s}}{{I}_{s}}=100\,\,W,\,\,{{V}_{p}}=220\,\,V,\,\,{{I}_{p}}=0.5\,\,A\] Hence, \[\eta =\frac{100}{220\times 0.5}=0.90=90%\] Note The efficiency of an ideal transformer is (or\[100%\]). But in practice due to loss in energy, the efficiency of transformer is always less than 1 (or less than\[100%\]).
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