NEET AIPMT SOLVED PAPER SCREENING 2007

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

    A)                  30%                      

    B)                  50%                      

    C)                  90%    

    D)                  10%

    Correct Answer: C

    Solution :

                    The efficiency of transfer \[\text{=}\frac{\text{Energy}\,\text{obtained}\,\text{from}\,\text{the}\,\text{secondary}\,\text{coil}}{\text{Energy}\,\text{given}\,\text{to}\,\text{the}\,\text{primary}\,\text{coil}}\] \[\text{or}\eta \text{=}\frac{\text{Output}\,\text{power}}{\text{Input}\,\text{power}}\] \[or\eta =\frac{{{V}_{s}}{{I}_{s}}}{{{V}_{p}}{{I}_{p}}}\] Given,  \[{{V}_{s}}{{I}_{s}}=100\,W,\,{{V}_{p}}=220\,\,V,\,{{I}_{p}}=0.5\,A\] Hence,  \[\eta =\frac{100}{220\times 0.5}=0.90=90%\]


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