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...
Non resistive terminations The situation becomes much more complex but still tractable when we consider non resistive terminations at the load end. As an example we will consider as shown in Figure 2.14 a transmission line terminated at the load end by a capacitance C. The structure is again exc...
Perfect conductor concept We take a practical view of the term perfect conductor to mean a material with very high conductivity, such as a metal, within which any electric field must be negligibly small, but we can still establish a steady value of magnetic field H and magnetic flux density B, i...
Phasor Notation We remind ourelves that the relation between time domain and frequency domain (phasor) variables is expressed by v(z, t) = ...
Plane wave terminology In the above equation the first factor changes amplitude, the second changes phase. The directions of maximum rates of change of amplitude and phase are α and β respectively. The plane perpendicular to β is a plane of constant phase; that such planes exist is why solutions...
Possibility of a surface charge We note in particular that a surface charge density ρs can exist, in many situations, even though not all. It can, for example, exist as a d.c. value on the surface of any material, i.e. a perfect insulator, (after it has been rubbed with the cat), on a non-insula...
Possible interior fi elds We are going for definiteness to make medium 1 the perfect conductor. In this medium there can be no electric field, either time-varying or static, and thus no electric flux density, either time-varying or static. Bec...
Power dissipation per unit area If we calculate the time average power dissipated per unit area of the interface, this is Wa = Z ∞ 0 Wvdz = Z ∞ 0 2|H0|2e−2z/δ 2σδ2 dz = |H0|2 2σδ = |Kx|2 2σδ (9.20) This is the same result as we would have obtained if the current had been assumed t...
