chapt02 - CHAPTER 2 COULOMB'S LAW AND ELECTRIC FIELD...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER 2 COULOMB'S LAW AND ELECTRIC FIELD INTENSITY Now that we have formulated a new language in the first chapter, we shall establish a few basic principles of electricity and attempt to describe them in terms of it. If we had used vector calculus for several years and already had a few correct ideas about electricity and magnetism, we might jump in now with both feet and present a handful of equations, including Maxwell's equations and a few other auxiliary equations, and proceed to describe them physically by virtue of our knowledge of vector analysis. This is perhaps the ideal way, starting with the most general results and then showing that Ohm's, Gauss's, Coulomb's, Faraday's, Ampe Á re's, Biot-Savart's, Kirchhoff's, and a few less familiar laws are all special cases of these equations. It is philosophically satisfying to have the most general result and to feel that we are able to obtain the results for any special case at will. However, such a jump would lead to many frantic cries of ``Help'' and not a few drowned students. Instead we shall present at decent intervals the experimental laws men- tioned above, expressing each in vector notation, and use these laws to solve a 27
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
number of simple problems. In this way our familiarity with both vector analysis and electric and magnetic fields will gradually increase, and by the time we have finally reached our handful of general equations, little additional explanation will be required. The entire field of electromagnetic theory is then open to us, and we may use Maxwell's equations to describe wave propagation, radiation from antennas, skin effect, waveguides and transmission lines, and travelling-wave tubes, and even to obtain a new insight into the ordinary power transformer. In this chapter we shall restrict our attention to static electric fields in vacuum or free space . Such fields, for example, are found in the focusing and deflection systems of electrostatic cathode-ray tubes. For all practical purposes, our results will also be applicable to air and other gases. Other materials will be introduced in Chap. 5, and time-varying fields will be introduced in Chap. 10. We shall begin by describing a quantitative experiment performed in the seventeenth century. 2.1 THE EXPERIMENTAL LAW OF COULOMB Records from at least 600 B.C. show evidence of the knowledge of static electri- city. The Greeks were responsible for the term ``electricity,'' derived from their word for amber, and they spent many leisure hours rubbing a small piece of amber on their sleeves and observing how it would then attract pieces of fluff and stuff. However, their main interest lay in philosophy and logic, not in experi- mental science, and it was many centuries before the attracting effect was con- sidered to be anything other than magic or a ``life force.'' Dr. Gilbert, physician to Her Majesty the Queen of England, was the first to do any true experimental work with this effect and in 1600 stated that glass, sulfur, amber, and other materials which he named would ``not only draw to
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/30/2010 for the course EE 2317 taught by Professor Wilton during the Spring '10 term at University of Houston.

Page1 / 26

chapt02 - CHAPTER 2 COULOMB'S LAW AND ELECTRIC FIELD...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online