Application of Gauss's Law: Electric field of charges of spherical symmetry The sphere's radius is R,the charge density of it is p E= PR (r≥R) E pr (r<R) 38。Application of Gauss’s Law: Electric field of charges of spherical symmetry :  R r The sphere’s radius is R, the charge density of it is  . 2 0 3 3 r R E    ( r ≥ R ) o r E   3  （r < R）