JEE Main & Advanced Sample Paper JEE Main Sample Paper-6

  • question_answer
    If electric potential due to some charge distribution is given by V = 3/r2 when r is radial distance, then find electric field at (1, 1, 1).

    A)  \[\frac{2}{\sqrt{3}}\]                                    

    B)  \[\frac{2(\hat{i}+\hat{j}+\hat{k})}{3}\]

    C)  \[\frac{2}{8(\hat{i}+\hat{j}+\hat{k})}\]                

    D)  \[\frac{3}{2(\hat{i}+\hat{j}+\hat{k})}\]

    Correct Answer: B

    Solution :

    \[V=\frac{3}{{{r}^{2}}}\] \[\overrightarrow{E}=-\left( \frac{dV}{dr} \right)\hat{r}=-\frac{\partial }{\partial r}\left[ \frac{3}{{{r}^{2}}} \right]\hat{r}=\frac{6}{{{r}^{4}}}\overrightarrow{r}\] \[E=6\frac{(\hat{i}+\hat{j}+\hat{k})}{{{(\sqrt{3})}^{4}}}=\left( \frac{2}{3} \right)(\hat{i}+\hat{j}+\hat{k})\]


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