Question

The distance between the two charges $25\, \mu C$ and $36\, \mu C$ is $11 \,cm$. At what point on the line joining the two, the intensity will be zero?

• A. At a distance of $5\, cm$ from $25\, \mu C$
• B. At a distance of $5 \,cm$ from $36 \,\mu C$
• C. At a distance of $10 \,cm$ from $25\, \mu C$
• D. At a distance of $11 \,cm$ from $36 \,\mu C$

Answer 1

Answer: (A)

Suppose electric field is zero at point $N$ in the figure. Then at $N$,

$\left|E_{1}\right|=\left|E_{2}\right|$
which gives $x_{1}=\frac{x}{\sqrt{\frac{Q_{2}}{Q_{1}}}+1}$
$=\frac{11}{\sqrt{\frac{36}{25}+1}}=5\,cm$