The rotational kinetic energy and translational kinetic energy of a rolling body are same, the body is

Two concentric circular coils A and B have radii $$20 \mathrm{~cm}$$ and $$10 \mathrm{~cm}$$ respectively lie in the same plane. The current in coil A is $$0.5 \mathrm{~A}$$ in anticlockwise direction. The current in coil B so that net field at the common centre is zero, is

A charged spherical conductor of radius '$$R$$' is connected momentarily to another uncharged spherical conductor of radius '$$r$$' by means of a thin conducting wire, then the ratio of the surface charge density of the first to the second conductor is

The magnet is moved towards the coil with speed '$$\mathrm{V}$$'. The induced e.m.f. in the coil is '$$\mathrm{e}$$'. The magnet and the coil move away from one another each moving with speed '$$\mathrm{V}$$'. The induced e.m.f. in the coil is