ABSTRACT
This chapter talks about the force experienced by current-carrying conductors when in magnetic fields, the basic principle behind direct current (DC). Magnetic lines of force can be thought of as lines along which something flows, this being termed flux. When any material is placed in a magnetic field, the extent to which the magnetic field permeates the medium when compared with what would happen in a vacuum is known as the relative permeability. Lines of magnetic flux form closed paths and the complete closed path followed by magnetic flux is called a magnetic circuit. In an electric circuit an electric current is due to the existence of an electromotive force (e.m.f.) and thus, by analogy, people say that in a magnetic circuit the magnetic flux is due to the existence of a magnetomotive force (m.m.f.). A magnetomotive force is produced by a current flowing through one or more turns of wire.
