The magnetic fields of isolated moving charges

THE AIM of electromagnetic theory is to investigate the properties of electromagnetic fields and relations to their sources. One problem in the latter category which is of some interest is that of determining the magnetic field due to a moving electric point charge. It is observed that the field is “proportional to the magnitude of the charge, its velocity, and the sine of the angle its velocity makes with the line joining it to the point of observation, and inversely proportional to the square of the distance from the charge to the point of observation.”