JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    A circular coil of diameter \[d\] is rotated in electric field such that electric flux is changed from zero to maximum value \[\phi \] then, electric field is:

    A) \[\frac{\phi }{\pi {{d}^{2}}}\]                                      

    B) \[\frac{2\phi }{\pi {{d}^{2}}}\]

    C)  \[\frac{4{{d}^{2}}}{\pi {{\phi }^{2}}}\]                                   

    D)  \[\frac{4\phi }{\pi {{d}^{2}}}\]

    Correct Answer: D

    Solution :

    From Gauss's theorem                 \[\int{E\cdot ds}=\phi \] where \[E\] is electric field intensity, \[s\] the surface area, \[\phi \] the flux. Given,   \[s=\pi {{r}^{2}}=\pi {{\left( \frac{d}{2} \right)}^{2}}=\frac{\pi {{d}^{2}}}{2}\] where \[r\] is radius and \[d\] the diameter.                 \[\phi =E\times \frac{\pi {{d}^{2}}}{4}\] \[\Rightarrow \]               \[E=\frac{4\phi }{\pi {{d}^{2}}}\]


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