Two small equal point charges of magnitude q are suspended from a common point on the ceiling by insulating massless strings of equal lengths. They come to equilibrium with each string making angle θ from the vertical. If the mass of each charge is m, then the electrostatic potential at the centre of line joining them will be

Two identical conducting spheres A and B, carry equal charge. They are separated by a distance much larger than their diameters, and the force between them is F. A third identical conducting sphere, C, is uncharged. Sphere C is first touched to A, then to B, and then removed. As a result, the force between A and B would be equal to :

Two charges + and -2 are located at points A and B on a horizontal line as shown below

The electric field is zero at a point which is located at a finite distance

Two spheres carrying charges +6μC and +9μC, separated by a distance d, experiences a force of repulsion F. When a charge of -3μC is given to both the sphere and kept at the same distance as before, the new force of repulsion is

Three charges, each +q, are placed at the corners of an isosceles triangles ABC of sides BC and AC, 2a. D and E are the mid-points of BC and CA. The work done in taking a charge Q from D to E is

A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each of the other two corners. If the net electrical force on q is zero, then q/Q equals:

 

Two spherical conductor B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor having same radius as that of B but uncharged brought in contact with B, then brought in contact with C and finally removed away from both. The new force of repulsion, between B and C is

Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 30 º with each other. When suspended in a liquid of density 0.8 g cm^–3, the angle remains the same. If density of the material of the sphere is 1.6 g cm^–3, the dielectric constant of the liquid is