An unchanged conducting sphere of radius R is placed near a uniformly charge ring of radius R. Total charge on ring is Q. The centre of sphere lies on axis of ring and distance of centre of sphere from centre of ring is R

Potential on the axis of ring of radius 3R and at distance 4R from centre of ring is (charge on the ring is Q )

Charge q is uniformly distributed over a thin half ring of radius R . The electric field at the centre of the ring is

A ring of radius R is charged uniformly with a charge +Q . The potential at a point on its axis at a distance 'r' from any point on ring will be-

A hollow metal sphere of radius R is uniformly charged. The electric field due to the sphere at a distance r from the centre

A uniform ring of mass M and radius R is placed directly above a uniform sphere of mass 8M and of same radius R. The centre of the ring is at a distance of d = sqrt(3)R from the centre of the sphere. The gravitational attraction between the sphere and the ring is

Charges q is uniformly distributed over a thin half ring of radius R . The electric field at the centre of the ring is