Page 24 - Maxwell House

4 Chapter 1

approximately 4 Joules are required to raise the temperature of 1 gram water by 1°C. Thereby,
the macroscopic electrodynamics considers electric and magnetic fields and all values
connected to them might be averaged and continuous. There is similar approach is in the
handling of electrical charges, the main source of electromagnetic waves. Experiments show
that an electrical charge is quantized and the smallest charge portion is only =
1.60217657x10 −19 Coulombs which corresponds to the charge of an electron (- e), proton (+
e), muon (- e), and several other elementary particles. Note that such elementary particles as
quarks and antiquarks carry fractional charges ± 2 3 or ± 1 3, i.e. less than that of an
⁄
⁄
electron. Consequently, in macroscopic electrodynamics charge quantization is disregarded,
and the averaged charge distribution is considered continuous. In other words, this book about
the continuum electrodynamics that lets us define physical objects of infinitesimal physical sizes
and introduce the limits like lim (∆ ∆), where the charge ∆ is spread continuously
⁄
∆→0
throughout a volume ∆ . As long as possible we will stay inside the borders of classical
electrodynamics and just go beyond to some extent analyzing the interaction of electromagnetic
waves with matter. Electromagnetic waves of different frequencies are an integral part of our
life. We cannot escape them, our body itself generates them, we used them extensively for
communication, broadcasting, energy generation and transportation, visualization, etc. The
range of electromagnetic waves ordered by frequency in cycles per second either wavelength
in meters, or energy of single photon in electron volts is called the electromagnetic spectrum
1
and shown in Figure 1.1.1 . The portion of the spectrum that is generally out of the reach of
classical electrodynamics is marked in rose. Note that outside Maxwell’s classical equations
there remains such phenomena as the radiation and absorption of electromagnetic waves of
ultra-high frequencies (e.g., light), photoelectric effect, single-photon light detector, and
many other effects involving quantum phenomena.
1.1.2 Vector and Scalar Fields

Classical electrodynamics describes a broad range of electromagnetic phenomena through
four vectors of electromagnetic fields (see Table 1.1) depending on time and three Cartesian
coordinates (x, y, z) or one vector = + + , where , , are the basis vectors
0
0
0
0
0
0
of unit length (see Figure A1 of the Appendix).
Table 1.1
Field Vector Denotation
E(, ) Electric field strength, defined by force interaction
B(, ) Magnetic induction strength, determined by force interaction
D(, ) Electric displacement strength
H(, ) Magnetic field strength

Four scalar primary sources of these fields are listed in Table 1.2.
Table 1.2
Source Denotation
(, ) Electric charge

1 Public Domain Image, source: www.flickr.com/photos/advancedphotonsource/5940581568