Chapter 9. Electromagnetic Interference (EMI)
Current is the flow of electrons. When electrons move down a trace or a wire, current flows. Electrons are negatively charged particles. Therefore, we can envision that there is an electrical (negative) charge around a wire as current flows, and the magnitude of this charge depends on the number of electrons (magnitude of the current). We call this charge an electric field. Furthermore, as the current flow changes in magnitude, this electric field changes in intensity.
Also, as electrons flow, a magnetic field is generated around the wire or trace. Andre Marie Ampere, for whom the measure of current is named, is credited as the first person to state this law. This is the basic relationship ...