Electrostatics

313 Pages·19.482 MB·English

by  Hilary D. Brewster

ELECTROSTATICS

ELECTROSTATICS
Hilary. D. Brewster
Oxford
Book Company
Jaipur India
I
ISBN: 978-93-80179-00-1
First Edition 2009
Oxford Book Company
267, JO-B-Scheme, Opp. Narayan Niwas,
Gopalpura By Pass Road, Jaipur-302018
Phone: [phone], Fax: [phone]
e-mail: [email protected]
website: www.oxfordbookcompany.com
© Reserved
Typeset by:
Shivangi Computers
267, 10-B-Scheme, Opp. Narayan Niwas,
Gopalpura By Pass Road, Jaipur-302018
Printed at:
Rajdhani Printers, Delhi
All Rights are Reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording, scanning or otherwise, without the prior written permission of the copyright owner.
Responsibility for the facts state,; opinions expressed, conclusions reached and plagiarism, ifany,
in this volume is entirely that of the Author, according to whom the matter encompassed in this
book has been originally created/edited and resemblance with any such publication may be
incidental. The Publisher bears no responsibility forthem, whatsoever.
· Preface
This book 'Electrostatics' on the physics of electricity, magnetism,
and electromagnetic fields and waves. It is written mainly with the physics
student in mind, although it will also be of use to students of electrical
and electronic engineering. The major aspects of the electrical field
including atomic structure and basic electricity, direct and alternating
current, basic circuit theory, three-phase circuits, single phase,
transformers, generators, and motors.
All studerlts of physics need to understand the basic concepts of
electricity and magnetism. E&M is central to the study of physics, and
central tc understanding the developments of the last two hundred years
of not just science, but technology. But the core of electricity and
magnetism can be difficult to understand - many of the ideas are
counterintui.tive and difficult to appreciate.
This as a basis, it is possible to develop all of electromagnetic theory
from a single experimental postulate founded on Coulomb's law. An
enriched understanding of magnetism results, and the Biot-Savart law is
a consequence rather than a postulate. The Lorentz force law is seen to
be a transformation of Coulomb's law occasioned by the relativistic
interpretation of force.
Upon accepting the Lorentz force law as fundamental, one is able to
derive Faraday's emf law and Maxwell's equations as additional
consequences. This procedure provides the further satisfaction of
demonstrating that the fields contained in the Lorentz force law and in
Maxwell's equations are one and the same, a conclusion not possible in
the conventional development of the subject.
Hilary. D. Brewster
I
I
I
I
I
I
I
I
I
I
Contents
Preface v
l. Matter and Electricity 1
2. Ohm's and Kirchhoff's Laws 46
3. Series Circuits and Parallel Circuits 86
4. Magnetism and Electromagnetism 133
5. Transistors 155
6. Resonance 190
7. Alternating Current 200
8. Generators and Motors 238
Index 301

Chapter 1
Matter and Electricity
ELECTRIC CHARGE: A PROPERTY OF MATTER
As with all other physical phenomena associated with motion, the
"explanation" of electrical phenomena starts only with observations. The
experiments are more difficult to replicate and harder to explain than those
relevant for motion.
Still, if you compare enough observations involving static electrical
phenomena (e.g. dragging your feet across a carpet and touching a door
handle, rubbing plastic piping with cotten, etc.) you can, as Benjamin
Franklin did, arrive at the following conclusion: Matter can have a physical
property which we call electrical charge
Electrical charge, like mass, is an intrinsic property of matter. It shares
many of the properties of mass in fact. The most important ones that we
have discovered over the ages are that
• Charges create and are subject to electrical forces.
• Charges can neither be created nor destroyed, i.e. they are intrinsic
to matter.
In addition, there are some things that charges do not share in common
with mass:
• Charges come in two types: designated as positive and negative.
• Charge is conserved as stated above, but it can readily be
transferred from one object to another as long as the object is
not a fundamental particle (e.g. an electron).
That last caveat is important. It turns out that, ultimately, charge and
mass do share the property of being intrinsic to matter, i.e. elementary
particles have a definite mass and a it fixed charge. Thus, the fact that we
can transfer electrical charges between objects is explained by stating that
this takes place by the actual exchange of charged particles.
Thus, the charges involved ar~ not created or destroyed anywhere,
just transferred from one object to another by the exchange of small
(essentially invisible) charged particles (which we no\y know are usually,
but not always, electrons).