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J & K CET Medical J & K - CET Medical Solved Paper-2012

  • question_answer
    A uniform magnetic field B points vertically up and is slowly changed in magnitude, but not in direction. The rate of change of the magnetic field is a. A conducting ring of radius r and resistance R is held perpendicular to the magnetic field, and is totally inside it. The induced current in the ring is

    A)  zero              

    B)  \[\frac{2\pi rB}{R}\]

    C)  \[\frac{r\alpha }{R}\]

    D)  \[\frac{\pi {{r}^{2}}\alpha }{R}\]

    Correct Answer: D

    Solution :

     The magnitude of the induced emf in the ring \[|\varepsilon |=\frac{d\phi }{dt}\] \[=\frac{d}{dt}(BA)\] \[=A\frac{d}{dt}B\] \[=\pi r\alpha \] The induced current in the ring \[I=\frac{\varepsilon }{R}=\frac{\pi {{r}^{2}}\alpha }{R}\]


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