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12th Class Physics Electro Magnetic Induction Question Bank MCQ - Electromagnetic Induction

  • question_answer
    A wheel with 20 metallic spokes each of length 0.5m long is rotated with a speed of 120 revolution per minute in a plane, normal to the horizontal component of earth magnetic field H at a place. If \[H=0.4\times {{10}^{-4}}T\] at the place, then induced emf between the axle and the rim of the wheel is:

    A) \[6.28\times {{10}^{-5}}V\]                 

    B) \[3.14\times {{10}^{-5}}V\]

    C) \[1.256\times {{10}^{-5}}V\]    

    D) \[1.57\times {{10}^{-5}}V\]

    Correct Answer: A

    Solution :

    (a) \[6.28\times {{10}^{-5}}V\] Here,    \[v=\frac{120}{60}=2\,rps\] Induced emf \[=\left( \frac{1}{2} \right)\omega B{{R}^{2}}=\frac{1}{2}2\pi vB{{R}^{2}}\]             \[=3.14\times 2\times 0.4\times {{10}^{-4}}\times {{(0.5)}^{2}}\]             \[=0.628\times {{10}^{-4}}=6.28\times {{10}^{-5}}V\]


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