Take risks: if you win, you will be happy; if you lose you will be wise.
Having mastered some essential mathematical tools needed for this course, we are now
prepared to study the basic concepts of EM. We shall begin with those fundamental con-
cepts that are applicable to static (or time-invariant) electric fields in free space (or
vacuum). An electrostatic field is produced by a static charge distribution. A typical
example of such a field is found in a cathode-ray tube.
Before we commence our study of electrostatics, it might be helpful to examine briefly
the importance of such a study. Electrostatics is a fascinating subject that has grown up in
diverse areas of application. Electric power transmission, X-ray machines, and lightning
protection are associated with strong electric fields and will require a knowledge of elec-
trostatics to understand and design suitable equipment. The devices used in solid-state
electronics are based on electrostatics. These include resistors, capacitors, and active
devices such as bipolar and field effect transistors, which are based on control of electron
motion by electrostatic fields. Almost all computer peripheral devices, with the exception
of magnetic memory, are based on electrostatic fields. Touch pads, capacitance keyboards,
cathode-ray tubes, liquid crystal displays, and electrostatic printers are typical examples.
In medical work, diagnosis is often carried out with the aid of electrostatics, as incorpo-
rated in electrocardiograms, electroencephalograms, and other recordings of organs with
electrical activity including eyes, ears, and stomachs. In industry, electrostatics is applied
in a variety of forms such as paint spraying, electrodeposition, electrochemical machining,
and separation of fine particles. Electrostatics is used in agriculture to sort seeds, direct
sprays to plants, measure the moisture content of crops, spin cotton, and speed baking of
bread and smoking of meat.
'For various applications of electrostatics, see J. M. Crowley,
Fundamentals of Applied Electrostat-
New York: John Wiley & Sons, 1986; A. D. Moore, ed.,
Electrostatics and Its Applications.
York: John Wiley & Sons, 1973; and C. E. Jowett,
Electrostatics in the Electronics Environment.
New York: John Wiley & Sons, 1976.
An interesting story on the magic of electrostatics is found in B. Bolton,
Electromagnetism and Its
London: Van Nostrand, 1980, p. 2.