Abstract: An error of judgment in some papers is discussed. By the conservation law of charge it is proved that, the divergence of the electric field E = ±v × B caused by a rotating magnetic field is not a nature cognate with true volume density of charge, but only a relativistic effect. And by the transformation of electromagnetic fields, a solution method of surface density of charge and electromagnetic field of an axially symmetric conductor rotating in a uniform steady magnetic field is given. The surface density of charge and electromagnetic field of a conducting sphere rotating in a uniform steady magnetic field are also obtained.

Key words: magnetic field and rotating conductor, relativistic effect and transformation, conservation of charge