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Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2008

  • question_answer
    The primary and secondary coils of a transformer have 50 and 1500 rums respectively. If the magnetic flux ^ linked with the primary coil is given by\[\phi ={{\phi }_{0}}+4t,\] where \[\phi \] is in we ber, t is time in second and \[{{\phi }_{0}}\] is a constant, the output voltage across die secondary coil is                   

    A)  90 V                                     

    B)  120 V

    C)  220 V                                   

    D)  30 V

    Correct Answer: B

    Solution :

    The magnetic flux linked with the primary coil is given by \[\phi ={{\phi }_{0}}+4t\] So, voltage across primary                 \[{{V}_{P}}=\frac{d\phi }{dt}=\frac{d}{dt}({{\phi }_{0}}+4t)\]                 \[=4volt\] (as \[{{\phi }_{0}}\] = constant) Also, we have \[{{N}_{P}}=50\]and \[{{N}_{S}}=1500\] From relation,                 \[\frac{{{V}_{s}}}{{{V}_{p}}}=\frac{{{N}_{s}}}{{{N}_{p}}}\] or            \[{{V}_{s}}={{V}_{p}}\frac{{{N}_{s}}}{{{N}_{p}}}\]                 \[=4\left( \frac{1500}{50} \right)\]                 \[=120V\] Note As in case of given transformer,, voltage in secondary is increased, hence  it is , a step-up transformer.


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