Question

Two point charges $q_1\left(\sqrt{10}\mu C\right)$ and $q_2(-25\mu C)$ are placed on the x-axis at x=1 m and x=4 m respectively. The electric field (in v/m) at a point y=3 m on y-axis is,

• A. $(-63\hat{i}+27\hat{j})\times {10}^2$
• B. $(81\hat{i}-81\hat{j})\times {10}^2$
• C. $(-81\hat{i}+81\hat{j})\times {10}^2$
• D. $(63\hat{i}+27\hat{j})\times {10}^2$

Answer 1

The correct option is A $(-63\hat{i}+27\hat{j})\times {10}^2$

Two points charges

$q_1\left(\sqrt{10}\mu C\right)$

$q_2(-25\mu C)$

$x=1m$ and $x=4m$

The electric field (in $V/m$)

$y=3m$ on axis

$E=\frac{1}{4\pi {ϵ}_0}\frac{q_1{q}_2}{r^2}$

$=9\times {10}^9\times \frac{\sqrt{10}\times 25\times {10}^{-12}}{{\left(3\right)}^2}$ $=0.079$

hence $x=1m$ to

$x=2m$

$(-63\hat{i}+27\hat{j})\times {10}^2$