JEE Main & Advanced Sample Paper JEE Main - Mock Test - 38

  • question_answer
    A tower used for power transmission leaks a current I into the ground. The tower is assumed to be a rod having lower end to be hemispherical with radius b. Resistivity of ground is \[\rho \]. The potential difference between the lower end of the rod and a point inside the ground at a distance r is

    A) \[\frac{I\rho }{2\pi r}\]               

    B)        \[\frac{I\rho }{2\pi }\left[ \frac{1}{b}-\frac{1}{r} \right]\]

    C) \[\frac{I\rho }{2\pi b}\,In\,\frac{r}{b}\]                

    D) \[\frac{I\rho }{4\pi b}\,In\,\frac{r}{b}\]

    Correct Answer: B

    Solution :

    [b] \[J=\frac{I}{2\pi {{r}^{2}}}=\frac{E}{\rho }\] \[E=\frac{I\rho }{2\pi {{r}^{2}}}\] \[\Delta V=\frac{I\rho }{2\pi }\int\limits_{b}^{r}{\frac{1}{{{r}^{2}}}}dr=\frac{I\rho }{2\pi }\left( \frac{1}{b}-\frac{1}{r} \right)\]


You need to login to perform this action.
You will be redirected in 3 sec spinner