A particle having a charge $1.6\times {10}^{-19}\mathrm{C}$ enters midway between the plates of a parallel plate condenser. The initial velocity of the particle is parallel to the plate. A potential difference of $300 \mathrm{V}$ is applied to the capacitor plate. If the length of the plate is $10 \mathrm{cm}$ and separation $2 \mathrm{cm}$, calculate the greatest initial velocity for which the particles will not be able to come out of the plates. [The mass of the particle is $12\times {10}^{-24} \mathrm{kg}$

Three charges, each of value q, are placed at the corners of an equilateral triangle. A fourth charge Q is placed at the centre of the triangle. 

If $Q=-q$, will the charges at the corners move towards the centre or fly away from it towards the centre or fly away from it ?

Three charges, each of value q, are placed at the corners of an equilateral triangle. A fourth charge Q is placed at the centre of the triangle.

(ii) For what value of Q will the charges remain stationary? In  this situation, how much work is done in removing the charges to infinity ?

Charge $+q$ and $-q$ are located at the corners of a cube of side a as shown in the figure, Fig. $2.106$. Find the work done to separate the charges to infinite distance.