Electromagnetic Purification (EMP), which is a new technique of purification, has become one of research focuses because of its non-pollution, high-efficiency and less effect of the different density between the melt and nonmetallic inclusions. So AC magnetic field purification, which is one of the electromagnetic purification, has also become one of the main study hots because of its convenient application.In this paper, electromagnetic body force has been deduced on the base of the Maxwell equations and t...