A square surface of side L meter in the plane of the paper is placed in a uniform electric field $$E$$(volt/m) acting along the same plane at an angle $$\theta $$ with the horizontal side of the square as shown in figurre.


The electric flux linked to the surface, in units of volt m is

Two positives ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge on an electron)

Three concentric spherical shells have radii a, b and c (a < b < c) anf have surface charge densities $$\sigma $$, $$-$$$$\sigma $$ and $$\sigma $$ respectively. If V_A, V_B and V_C denote the potentials of the three shells, then, for c = a + b, we have

The electric potential at a point (x, y, z) is given by V = $$-$$x²y $$-$$ xz³ + 4

The electric field at that point is