Question

Two point charges $+3\mu C$ and $-3\mu C$ are kept $20cm$ apart in air. Find the electric field midway between the charges on the line joining them. What will be the force experienced by a charge $+1.5\times {10}^{-9}C$ placed at this point ?

Answer 1

$E_{net}$ at midway $=\frac{K.\theta }{r^2}+\frac{K.\theta }{r^2}=\frac{2K.\theta }{r^2}$

$\begin{array}{c}=\frac{9\times 10\times 9\times 3\times {10}^{-6}\times 2}{{\left(.10\right)}^2}\\ =\frac{54\times {10}^3}{01}\times 100\\ =54\times {10}^{5}N/C\end{array}$

$\begin{array}{c}F=9E=1.5\times {10}^{-9}\times 54\times {10}^5\\ =81\times {10}^{-4}N\end{array}$