A Second Look at a Fundamental Concept in Electromagnetics
Keywords: electric current, spinning charges, coulomb charge
It is worthwhile to examine more closely the concept that an electric current is defined by the product of charge times its velocity, or simply by the quantity of coulomb charge that passes a given point per unit time. It is suggested that this definition is sometimes inadequate to define the fields due to such a current, even if it is a d-c current, when the charge velocity is even a significant fraction of the speed of light. The fact will be demonstrated by analyzing the fields of a spinning charged ring on a time retarded basis. In the process, some interesting characteristics of spinning charges will be present.