Two point charges $$\mathrm{M}$$ and $$\mathrm{N}$$ having charges $$+q$$ and $$-q$$ respectively are placed at a distance apart. Force acting between them is $$\mathrm{F}$$. If $$30 \%$$ of charge of $$\mathrm{N}$$ is transferred to $$\mathrm{M}$$, then the force between the charges becomes:

If 216 drops of the same size are charged at $$200 \mathrm{~V}$$ each and they combine to form a bigger drop, the potential of the bigger drop will be

Three point charges are located on a circular arc at $$\mathrm{A}, \mathrm{B}$$ and $$\mathrm{C}$$ as shown in the figure below. The total electric field at the centre of the $$\operatorname{arc}(\mathrm{C})$$ is

A tiny ball of mass $$\mathrm{m}$$ and charge $$\mathrm{q}$$ is suspended from the fixed support using an insulating string of length $$1 \mathrm{~m}$$. The horizontal uniform electric field $$\mathrm{E}$$ is switched on. The angle made by the string with vertical when the ball is in equilibrium is $$45^{\circ}$$. The magnitude of uniform electric field is