Linear lossy ferromagnet If we are prepared to consider small signals, and the sinusoidal steady state, we canmodel the behaviour of a material in which the magnetisation lags somewhat behind a sinusoidal magnetic field excitation by the equations M = (χ0 m − jχ00 m) H (5.15) B = (μ0 − jμ00) ...
Linear magnetostatic case A not entirely parallel examination of the work done, perhaps by mechanical or perhaps by electrical means, to create a magnetic field leads to the result Um = 1 2 μ Z vH·Hdv (7.4) for the total energy stored. Of course in the case of a linear medium this result ha...
Linear soft ferromagnet In polycrystalline ferromagnets and for small values of internal field strength we may write to a reasonable level of approximation M= χm H (5.10) where χm is a dimensionless parameter called the magnetic susceptibility. The same relation may be expressed in the alternat...
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...
