Lumped Circuit Theory It is now appropriate to review the principles of that circuit theory, designated herein as lumped circuit theory as it has been studied at Levels 1 and 2, to recognise that the assumptions underlying that theory are rarely...
Magnetic e ff ects The magnetic effects are caused mainly by the spin of the electrons of which the matter is composed, sometimes by the orbital motion of the electrons in the atoms, and sometimes by the spin or motion of the other particles. Th...
Maxwells Equations in Conducting Media We quote first the constituent relations to see whether it is appropriate to use E and H or whether we need D and B as well. These are D = ²E B = μH J = σE (9.1) It is appropriate to continue to use E and H so Maxwell's equations are ∇ × E = −jω (μH) ∇...
Medium of large loss We say the medium has large loss (for transmission of waves through that medium) when σ À ω², i.e. conduction current À displacement current. Then the equations at the end of Section 9.2 can be put in the different approximate form γ ≈ (1 + j) r ωμσ 2 (9.10) and η ≈ (1...
Medium of small loss We say the medium has small loss when σ ¿ ω² i.e. conduction current ¿ displacement current. Then the above two equations can be put into the approximate forms α ≈ σ 2 r μ ² (9.7) i.e. half the product of the conductivity and wave impedance for a lossless medium, β ≈ ...
Method of Analysis Because of the discontinuities in the material parameters, and the discontinuities in at least some components of the electromagnetic field which result therefrom, Maxwell's equations in differential form fail, in the sense that the derivatives do not exist, at the boundary. M...
Method of matching When matching is performed in a transmission line context it is done in the way illustrated in Figure 3.1. In this figure two matching systems are illustrated. The matching system on the right is intended to transform the load impedance ZL so that it becomes equal to the chara...
Methods of energy input In a general electromagnetic system we can identify the following methods of exchanging energy between that system and its environment. • Moving charged bodies in an electric field. The forces on the charged bodies re...
Non linear but lossless dielectric A more general form of behaviour, which admits of some non-linearity in the material, but still does not involve energy loss, is described by the equation P = χe(E) ²0 E (5.5) where χe(E) is now a dimensionless dielectric susceptibility which depends on the ma...
Non linear but lossless ferromagnet For larger field strengths, the behaviour of a ferromagnet is better described by the hysteresis curve shown in Figure 5.1. In relation to that curve we take the opportunity to define in the figure the important concepts of saturation magnetisation M0 and coerc...
