JEE Main & Advanced Sample Paper JEE Main - Mock Test - 7

  • question_answer
    A circular coil of radius 8.0 cm and of 20 turns is rotated about its vertical diameter with an angular speed of 50 rad \[{{s}^{-1}}\]in a uniform horizontal magnetic field of magnitude \[3.0\times {{10}^{-2}}T\]. If the coil forms a closed loop of resistance \[10\Omega \], calculate the average power loss due to Joule heating.

    A)  9 mW              

    B)  18 Mw

    C)  27 mW         

    D)  36 mW

    Correct Answer: B

    Solution :

    [b]: The maximum value of the induced current, \[{{I}_{\max }}=\frac{\varepsilon \max }{R}=\frac{ABM\omega }{R}\]. Given, \[A=\pi {{r}^{2}}=3.14{{(8\times {{10}^{-2}}m)}^{2}},B=3\times {{10}^{-2}}T\], \[N=20,\omega =50\,\text{rad}\,{{s}^{-1}}\,\text{and}\,R=10\Omega \] \[\therefore \]\[{{I}_{\max }}=\frac{3.14{{\left( 8\times {{10}^{-2}}m \right)}^{2}}\left( 3\times {{10}^{-2}}T \right)\times 20\,(50\,\text{rad}\,{{\text{s}}^{\text{-l}}})}{10\Omega }\]\[=0.0603A\] The average power loss in the form of heat, \[{{P}_{av}}=\frac{1}{2}I_{\max }^{2}R=\frac{1}{2}{{(0.0603A)}^{2}}(10\Omega )\] \[=0.018\text{ }W=18\text{ }mW.\]


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