Question

In the question number $18$, the potential at a point $20\, cm$ from the mid-point of the line joining the two charges in a plane normal to the line and passing through the mid-point is

• A. $1.4 \times 10^{5} \, V$
• B. $4.2 \times 10^{3} \, V$
• C. $2.9 \times 10^{4} \, V$
• D. $3.7 \times 10^{5} \, V$

Answer 1

Answer: (A)

$1.4 \times 10^{5} \, V$

Answer 2

From the figure, potential at $P$, $V=\frac{q_{1}}{4\pi\varepsilon_{0}\left(PA\right)}+\frac{q_{2}}{4\pi\varepsilon_{0}\left(PB\right)}$ $=\frac{1}{4\pi\varepsilon_{0}\left(PA\right)}\left(q_{1}+q_{2}\right)$ $\left(\because PA=PB=\sqrt{\left(0.2\right)^{2}+\left(0.2\right)^{2}}=0.28\,m\right)$ $=\frac{9\times10^{9}\left(1.8+2.8\right)\times10^{-6}}{0.28}$ $=1.4\times10^{5}\,V$