The magnitude of electric force on $2 \mathrm{\mu C}$ charge placed at the centre $O$ of two equilateral triangles each of side $10 \mathrm{cm}$ as shown in figure is $P$. If charge $A, B, C, D, E$ and $F$ are $2 \mathrm{\mu C}, 2 \mathrm{\mu C}, 2 \mathrm{\mu C}, -2 \mathrm{\mu C}, -2 \mathrm{\mu C} \text{and} -2 \mathrm{\mu C}$ respectively, then $P$ is,

Two charges $+q$ and $-q$ are placed at a distance $b$ apart as shown in the figure below.

The electric field at a point $P$ on the perpendicular bisector as shown as :

$5$ charges each of magnitude ${10}^{-5} \mathrm{C}$ and mass $1 \mathrm{kg}$ are placed (fixed) symmetrically about a movable central charges of magnitude $5\times {10}^{-5} \mathrm{C}$ and mass $0.5 \mathrm{kg}$ as shown. The charges at $P_1$ is removed. The acceleration of the central charge is:

$\left[\mathrm{Given} O{P}_1=O{P}_2=O{P}_3=O{P}_4=O{P}_5=1 \mathrm{m}; \frac{1}{4\mathrm{\pi }{\epsilon }_0}=9\times {10}^9 \mathrm{in} \mathrm{Sl} \mathrm{units}\right]$