JEE Main & Advanced Physics Electrostatics & Capacitance JEE PYQ-Electrostatics and Capacitance

  • question_answer
    An electric field \[\overset{\to }{\mathop{E}}\,=\left( 25\,\hat{i}+30\hat{j} \right)N{{C}^{-1}}\] exists in a region of space. If the potential at the origin is taken to be zero then the potential at x = 2 m, y = 2 m is:             [JEE MAIN 11-04-2015]

    A) - 130J

    B) - 12.0J

    C) - 140J

    D) - 110J

    Correct Answer: D

    Solution :

    [d] \[\therefore \] \[\int_{{}}^{{}}{dV}=-\int_{{}}^{{}}{{\vec{E}}}.d\vec{r}\]
    \[d\vec{r}=dx\hat{i}+dy\hat{j}\]
    \[\int_{{}}^{{}}{dV=-}\int_{{}}^{{}}{\left( 25\hat{i}+30\hat{j} \right).\left( dx\hat{i}+dy\hat{j} \right)}\]
    \[\int_{0}^{v}{dV=-}\int\limits_{0}^{2}{25dx}+\int\limits_{0}^{2}{30dy}\]
    \[V-0=-\left[ 25\left( x \right)_{0}^{2}+30\left( y \right)_{0}^{2} \right]\]
    \[V=-\left[ 25\times 2+30\times 2 \right]\]
    \[V=-110\]volt \[=-110J/C\]


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