Ten charges are placed on the circumference of a circle of radius $10\mathrm{s}$ $$ with constant angular separation between successive charges. Alternate charges 1, 3, 5, 7, 9 have charge (+q)$$ each, while $\mathrm{2,4},\mathrm{6,8},10$ $$ have charge $$ (-q)each. The potential v$$ and the electric field $$ E at the centre of the circle are respectively: (Take V = 0 $$ at infinity)

Four metallic plates, each with a surface area A, are placed at a distance d from each other as shown in the figure. If points A and B is connected with a battery of emf V, then the charge on the plate a will be   

If q₁ + q₂ = 3q, then the value of the q₁/q₂, for which the force of repulsion between q₁ and q₂ is maximum is

A capacitor of 20 μF is charged to 500 volt and a capacitor 10μF is charged to 200 volt and connected. Then after connecting both of them, the common potential for each will be :–

Three charges Q,(+q) and (+q) are placed at the vertices of an equilateral triangle of side ℓ as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal to :-

 

A positive charge is moved from low potential point A to a high potential point B. Then the electric potential energy