JEE Main & Advanced JEE Main Paper (Held On 11 April 2015)

  • 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 Online Paper (Held On 11 April 2015)]  

    A)  -130J

    B)  -12.0J

    C)  -140J

    D)  -110J

    Correct Answer: D

    Solution :

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


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