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1. Electric Charges and Fields
medium
Two charges $e$ and $3 e$ are placed at a distance $r$. The distance of the point where the electric field intensity will be zero is .........
A
$\frac{r}{(1+\sqrt{3})}$ from $3 e$ charge
B
$\frac{r}{(1+\sqrt{3})}$ from $e$ charge
C
$\frac{r}{(1-\sqrt{3})}$ from $3 e$ charge
D
$\frac{r}{1+\sqrt{\frac{1}{3}}}$ from $e$ charge
Solution

(b)
Net electric field at $P$ is zero then
$O=E_1-E_2$
$E_1=E_2$
$\frac{k e}{x^2}=\frac{k 3 e}{(r-x)^2}$
so, $\frac{1}{x}=\frac{\sqrt{3}}{r-x}$
$r-x=\sqrt{3} x$
$r=x[1+\sqrt{3}]$
$x=\frac{r}{(1+\sqrt{3})}$
Standard 12
Physics