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  3. RAJASTHAN ­ PET

RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    A short circuited coil is placed in magnetic field at any time. Power loss in coil occurs due to generated induced current. If number of turns becomes 4 times and radius of wire becomes half, then the loss of electric power will be

    A)  half               

    B)  equal

    C)  two times       

    D)  four times

    Correct Answer: C

    Solution :

     Power \[P=\frac{{{e}^{2}}}{R}\]and \[e=-\frac{d\phi }{dt}\] Here,     \[\phi =NBA\] \[\therefore \] \[e=-NA\left( \frac{dB}{dt} \right)\] and       \[R\propto \frac{1}{{{r}^{2}}}\] \[P\propto {{N}^{2}}{{r}^{4}}\] \[\therefore \] \[\frac{{{P}_{1}}}{{{P}_{2}}}=1\]


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