Two concentric rings, one of radius a and the other of radius b, have the charges +q, and `-(2//5)^(-3//2)q`, respectively as shown in fig.

Find the rario `b//a` if a charge particle palaced on the axis at z =a is i equilibrium.

Two concentric coplanar rings one of radius a and the other of radius 2a, have charges qa and qb respectively. A charged particle is in equilibrium on their common axis at a distance a from the common centre. Then the ratio qa/qb is

Two concentric conducting shells of radius a and (gt a) carry charges Q and -2Q respectively. The correct variation of electric intensity E as a function of r is given by

Two identical coaxial rings each of radius R are separated by a distance of sqrt3R . They are uniformly charged with charges +Q and -Q respectively. The minimum kinetic energy with which a charged particle (charge +q ) should be projected from the centre of the negatively charged ring along the axis of the rings such that it reaches the centre of the positively charged ring is

Two concentric rings, one of radius R and total charge +Q and second of radius 2R and total charge -sqrt(8)Q , lie in x-y plane (i.e., z=0 plane). The common centre of rings lies at origin and the common axis coincides with z -axis. The charge is uniformly distributed on both rings. At what distance from origin is the net electric field on z -axis zero?

Two concentric spherical shells of radius R_(1) and R_(2) (R_(2) gt R_(1)) are having uniformly distributed charges Q_(1) and Q_(2) respectively. Find out total energy of the system.

Charges Q, 2Q , and -Q are given to three concentric conducting sphereical shells A, B and C respectively as shown in figure. The ratio of charge on the inner and outer surface of shell C will be

Two uniformly charged concentric spherical shells of radius R and r, are given charges Q_1 and Q_2 respectively. If their potential difference is V, then it will not depends upon:

Charges are placed at the corners of a square of side a as shown in the following figure. The charged particle placed at A is in equilibrium. The ratio (q_1)/(q_2) is

Two positive charges q_1 and q_2 are moving with velocities v_1 and v_2 when they are at points A and B, respectively, as shown in Fig. The magnetic force experienced by charge q_1 due to the other charge q_2 is

Three concentric spherical shells A, B and C having uniformly distributed total charges +Q, -2Q and +Q respectively are placed as shown. The potential at the centre will be -