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NEET Sample Paper NEET Sample Test Paper-13

  • question_answer
    A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at \[2mm{{s}^{-1}}.\] The induced emf in the loop when the radius is 2 cm is

    A)  \[3.2\,\pi \mu V\]                      

    B) \[4.8\,\pi \mu V\]

    C)  \[0.8\,\pi \mu V\]                      

    D)  \[1.6\,\pi \mu V\]

    Correct Answer: A

    Solution :

     According to Faraday's second law of electro- magnetic induction, the induced emf is given by the rate of change of magnetic flux linked with the circuit. Here, B = 0.0 4 T and\[\frac{-dr}{dt}=2\,mm{{s}^{-1}}\] Induced emf, \[e-\frac{-d\phi }{dt}=\frac{-BdA}{dt}=-B\frac{d(\pi {{r}^{2}})}{dt}\] \[=-B\pi 2r\frac{dr}{dt}\] Now, r = 2 cm \[e=-0.04\times \pi \times 2\times 2\times {{10}^{-2}}\times 2\times {{10}^{-3}}\] \[=3.2\,\pi \mu V\]


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