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# A point charge q=12.5 $\mu$C is placed at origin . Find the electric field vector at the point $\;(4 , 3)$ .

$(a)\;3.6 \hat{i}+1.8 \hat{j}\qquad(b)\;3.6 \hat{i}-2.7 \hat{j}\qquad(c)\;-3.6 \hat{i}+2.7 \hat{j}\qquad(d)\;3.6 \hat{i}+2.7\hat{j}$

Answer : (d) $\;3.6 \hat{i}+2.7 \hat{j}$
Explanation :
$\overrightarrow{E}=\large\frac{k\;q (\overrightarrow{r})}{|\overrightarrow{r}|^3}$
$\overrightarrow{r}=4\hat{i}+3\hat{j} \quad\;|\overrightarrow{r}=5|$
$\overrightarrow{E}=\large\frac{k\;q (4\hat{i}+3\hat{j})}{125}$
$\overrightarrow{E}=\large\frac{9\times10^{9}\times12.5\times10^{-9}(4\hat{i}+3\hat{j})}{125}$
$\overrightarrow{E}=3.6\hat{i}+2.7\hat{j}\;.$
edited Jan 30, 2014 by yamini.v