Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 55

An early model of the atomic structure of a chemical element was that the atom was a spherical cloud of uniformly distributed positive charge Ne, where N is the atomic number and e is the magnitude of electronic charge. Electrons, each carrying a negative charge -e, were considered to be imbedded in the cloud. Assuming the spherical charge cloud to have a radius R0 and neglecting collision effects,
a) find the force experienced by an imbedded electron at a distance r from the center;
b) describe the motion of the electron;
c) explain why this atomic model is unsatisfactory.