Two concentric rings are placed in a gravity-free region in the -plane
PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two concentric rings are placed in a gravity-free region in the YZ-plane. One ring, of radius r, carries charge +q, and the other, of radius 4r, carries charge −8q, uniformly distributed over it. Find the minimum velocity with which a point charge of mass m and charge +q should be projected from a point on their axis at a distance 3r from their centre, so that it reaches the centre of the rings.