JEE Main & Advanced Physics Electro Magnetic Induction Question Bank Self Evaluation Test - Electromagnetic Induction

  • question_answer
    A conducting circular loop is placed in a uniform magnetic field of 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is

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

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

    C) \[1.6\pi \mu \,V\]

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

    Correct Answer: D

    Solution :

    [d] Induced emf in the loop is given by \[e=-B.\frac{dA}{dt}\] where A is the area of the loop. \[e=-B.\frac{d}{dt}(\pi {{r}^{2}})=-B\,\pi 2r\frac{dr}{dt}\] \[r=2cm=2\times {{10}^{-2}}m\] \[dr=2mm=2\times {{10}^{-3}}m\], \[dt=1s\] \[e=-\,0.04\times 3.14\times 2\times 2\times {{10}^{-2}}\times \frac{2\times {{10}^{-3}}}{1}V\] \[=0.32\pi \times {{10}^{-5}}V=3.2\pi \times {{10}^{-6}}V=3.2\pi \mu V\]


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