Three point charges of $+2\mu C,-3\mu C$ and $-3\mu C$ are kept at the vertices A, B and C respectively of an equilateral triangle of side $20 \mathrm{cm}$ as shown in the Fig. $2.104$. What should be the sign and magnitude of the charge to be placed at the mid point (M) of side BC so that the charge at A remains in equilibrium?

A uniform electric field $\overrightarrow{E}$ of $300{\mathrm{NC}}^{-1}$ is directed along P Q A, B and C are three points in the field having x and y coordinates (in metres) as shown in the figure, Fig $2.105$. Calculate potential difference between points A and B.

A uniform electric field $\overrightarrow{E}$ of $300{\mathrm{NC}}^{-1}$ is directed along PQ  A, B and C are three points in the field having x and y coordinates (in metres) as shown in the figure, Fig $2.105$. Calculate potential difference between points B and C.

Two point charges $+10\mu \mathrm{C}$ and $-10\mu \mathrm{C}$ are separated by a distance of $40 \mathrm{cm}$ in air.

$\left(i\right)$ Calculate the electrostatic potential energy of the system, assuming the zero of the potential energy to be at infinity.

Two point charges $+10\mu \mathrm{C}$ and $-10\mu \mathrm{C}$ are separated by a distance of $40 \mathrm{cm}$ in air. Draw an equipotential surface of the system.