With both the spacing between the winding and the core and the nonuniform distribution of magnetic field in the crosssection of the core being taken into account, a formula for the core volume of a toroid magnetic switch is deduced.

A mathematical model of electromagnetic body force (EMF) in electromagnetic purification at magnetic field of high frequency was established, based on the influences of EMF distribution inside melt on purification effects in different experiment conditions.

The electromagnetic body forces, which is caused by the electromagnetic field and is localized on the circular cylinder surface, have been used to modify the boundary layer of flow and control the flow field of the circular-cylinder flow in electrolyte solution.