Digital-pulse approach to electromagnetism

The advantages of a change in approach to electromagnetism are explored. In place of the historical method, which bases magnetism on empirical observations and deduces propagation effects, the sequence is reversed by assuming a finite velocity of propagation and deriving the magnetic interactions. The starting point is the pulse, and the key relationship is the change in charge density which it causes. Attention is concentrated on the charges within the wires, rather than on the fields around them, by using the retarded potentials to express the electromagnetic interactions. Maxwell´s definition of the vector A in terms of electrokinetic momentum is adopted in place of the customary magnetic vector potential interpretation, and this is equivalent to a choice of energy density which attributes the electrostatic and magnetic energies to the charges, not the fields. It is shown that these changes have considerable advantages in simplicity, both of the concepts and the mathematical treatment, and that they provide a more direct insight into the relationship between the magnetic and electrostatic interactions. The magnetic field description can be derived at any point by differentiating A, but it is shown that this is unnecessary, and that students can gain a detailed understanding of electromagnetism unencumbered by the mathematical apparatus of vector field theory.