J & K CET Engineering J and K - CET Engineering Solved Paper-2014

  • question_answer
    A wheel with 30 metallic spokes each of \[7.0\text{ }m\] long is rotated with a speed of \[120\text{ }rev/min,\] in a plane normal to the horizontal component of the earth's magnetic field Hg /at a place. If \[{{H}_{E}}=0.8G\]at the place what is the induced emf between the axis and the rim of the wheel? (Give \[1G={{10}^{-4}}\text{ }T\])

    A)  \[2.46\times {{10}^{-4}}V\]     

    B)  \[6.28\times {{10}^{-4}}V\]

    C)  \[5.76\times {{10}^{-5}}V\]     

    D)  \[4.92\times {{10}^{-4}}V\]

    Correct Answer: A

    Solution :

    In the case of rotating wheel in a normal magnetic field induced emf \[=\frac{1}{2}\omega B{{R}^{2}}\] \[e=\frac{1}{2}\times 2\pi \left( \frac{120}{60} \right)\times 0.8\times {{10}^{-4}}\times {{(0.7)}^{2}}\] \[=2\pi \times 0.8\times {{10}^{-4}}\times 0.49=2.46\times {{10}^{-4}}V\]


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