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12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Case Based (MCQs) - Alternating Currents

  • question_answer
    A transformer is used to light 100 W-110 V lamp from 220V mains. If the main current is 0.5 A, the efficiency of the transformer is:

    A) 95%   

    B) 99%   

    C) 90%                             

    D) 96%

    Correct Answer: C

    Solution :

    (c) 90% The efficiency of the transformer is \[\eta =\frac{\text{Output}\,\,\text{power}\,\,\left( {{P}_{out}} \right)}{\text{Input}\,\,\text{power}\,\,\left( {{P}_{in}} \right)}\times 100\] Here,  \[{{P}_{out}}=100\,\,W,\,\,{{P}_{in}}=(220\,V)\,\,(0.5\,A)=110\,W\] \[\therefore \eta =\frac{100\,W}{110\,W}\times 100\approx 90%\]


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