Electricity and Magnetism

504 Pages·2011·171.78 MB·English

by  Edward M. Purcell

Electricity and Magnetism, Second Edition
For 40 years, Edward M. Purcell's classic textbook has introduced
students to the wonders of electricity and magnetism.
With profound physical insight, Purcell covers all the standard introductory
topics, such as electrostatics, magnetism, circuits, electromagnetic
waves, and electric and magnetic fields in matter.Taking a non-traditional
approach, the textbook focuses on fundamental questions from different
frames of reference. Mathematical concepts are introduced in parallel with
the physics topics at hand, making the motivations clear. Macroscopic
phenomena are derived rigorously from microscopic phenomena.
With hundreds of illustrations and over 300 end-of-chapter problems, this
textbook is widely considered the best undergraduate textbook on
electricity and magnetism ever written.
EDWARD M. PU RC ELL (1 91 2-1 997) was the recipient of many awards for
his scientific, educational, and civic work. In 1952 he shared the Nobel
Prize for Physics for his independent discovery of nuclear magnetic reso-
nance in liquids and in solids, an elegant and precise way of determining
chemical structure and properties of materials which is widely used today.
During his career he served as science advisor to Presidents Dwight D.
Eisenhower, John F. Kennedy, and Lyndon B. Johnson.

SECOND EDITION
ELECTRICITY
AND MAGNETISM
CAMBRIDGE
UNIIYERSITT PRESS
CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town,
Singapore, S5o Paulo, Delhi, Dubai, Tokyo, Mexico City
Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
Published in the United States of America by Cambridge University Press, NewYork
www.cambridge.org
Information on this title: www.cambridge.org/9781107013605
O Dennis and Frank Purcell2011
This edition is not for sale in India
Previously published by McGraw-Hill, Inc 1985
First edition published by Education Development Center, Inc 1963, 1964, 1965
First published by Cambridge University Press 201 1
Printed in the United Kingdom at the University Press, Cambridge
A catalog record for this publication is available from the British Library
ISBN 978-1- 1 07-013 60-5 Hardback
Cambridge University Press has no responsibility for the persistence or
accuracy of URLs for external or third-party internet websites referred to in
this publication, and does not guarantee that any content on such websites is,
or will remain, accurate or appropriate.
Preface to the Second Edition of Volume 2 CONTENTS
xi
Preface to the First Edition of Volume 2 xv
Preface to the Berkeley Physics Course xvi~
CHAPTER 1
ELECTROSTATICS: CHARGES AND FIELDS
1.1 Electric Charge
1.2 Conservation of Charge
1.3 Quantization of Charge
1.4 Coulomb's Law
1.5 Energy of a System of Charges
1.6 Electrical Energy in a Crystal Lattice
1.7 The Electric Field
1.8 Charge Distributions
1.9 Flux
1.10 Gauss's Law
1.1 1 Field of a Spherical Charge Distribution
1.12 Field of a Line Charge
1.13 Field of an Infinite Flat Sheet of Charge
1.14 The Force on a Layer of Charge
1.15 Energy Associated with the Electric Field
Problems
CONTENTS
CHAPTER 2
THE ELECTRIC POTENTIAL
2.1 Line Integral of the Electric Field
2.2 Potential Difference and the Potential Function
2.5 Gradient of a Scalar Function
2.4 Derivation of the Field from the Potential
2.5 Potential of a Charge Distribution
Potential of Two Point Charges
Potential of a Long Charged Wire
2.6 Uniformly Charged Disk
2.7 Divergence of a Vector Function
2.8 Gauss's Theorem and the Differential Form
of Gauss's Law
2.8 The Divergence in Cartesian Coordinates
2.10 The Laplacian
2.1 1 Laplace's Equation
2.12 Distinguishing the Physics from the Mathematics
2.15 The Curl of a Vector Function
2.1 4 Stokes' Theorem
2.15 The Curl in Cartesian Coordinates
2.16 The Physical Meaning of the Curl
Problems
CHAPTER 5
ELECTRIC FIELDS AROUND CONDUCTORS
Conductors and Insulators
Conductors in the Electrostatic Field
The General Electrostatic Problem;
Uniqueness Theorem
Some Simple Systems of Conductors
Capacitance and Capacitors
Potentials and Charges on Several Conductors
Energy Stored in a Capacitor
Other Views of the Boundary-Value Problem
Problems
CHAPTER 4
ELECTRIC CURRENTS
4.1 Electric Current and Current Density 124
4.2 Steady Currents and Charge Conservation 126
4.5 Electrical Conductivity and Ohm's Law 128
4.4 The Physics of Electrical Conduction 133
4.5 Conduction in Metals 142
CONTENTS vii
4.6 Semiconductors
4.7 Circuits and Circuit Elements
4.8 Energy Dissipation in Current Flow
4.8 Electromotive Force and the Voltaic Cell
4.10 Networks with Voltage Sources
4.1 1 Variable Currents in Capacitors and Resistors
Problems
CHAPTER 5
THE FIELDS OF MOVING CHARGES
5.1 From Oersted to Einstein
5.2 Magnetic Forces
5.5 Measurement of Charge in Motion
5.4 lnvariance of Charge
5.5 Electric Field Measured in Different Frames
of Reference
5.6 Field of a Point Charge Moving with
Constant Velocity
5.7 Field of a Charge That Starts or Stops
5.8 Force on a Moving Charge
5.8 Interaction between a Moving Charge and
Other Moving Charges
Problems
CHAPTER 6
THE MAGNETIC FIELD
Definition of the Magnetic Field
Some Properties of the Magnetic Field
Vector Potential
Field of Any Current-Carrying Wire
Fields of Rings and Coils
Change in B at a Current Sheet
How the Fields Transform
Rowland's Experiment
Electric Conduction in a Magnetic Field:
The Hall Effect
Problems
CHAPTER 7
ELECTROMAGNETIC INDUCTION
7.1 Faraday's Discovery
7.2 A Conducting Rod Moving through a Uniform
Magnetic Field
viii CONTENTS
A Loop Moving through a Nonuniform
Magnetic Field
A Stationary Loop with the Field Sources Moving
A Universal Law of Induction
Mutual Inductance
A Reciprocity Theorem
Self-inductance
A Circuit Containing Self-inductance
Energy Stored in the Magnetic Field
Problems
CHAPTER 8
ALTERNATING-CURRENT CIRCUITS
8.1 A Resonant Circuit
8.2 Alternating Current
8.5 Alternating-Current Networks
8.4 Admittance and Impedance
8.5 Power and Energy in Alternating-Current
Circuits
Problems
CHAPTER 8
MAXWELL'S EQUATIONS
AND ELECTROMAGNETIC WAVES
8.1 "Something Is Missing"
8.2 The Displacement Current
8.5 Maxwell's Equations
8.4 An Electromagnetic Wave
8.5 Other Waveforms; Superposition of Waves
8.6 Energy Transport by Electromagnetic Waves
8.7 How a Wave Looks in a Different Frame
Problems
CHAPTER 10
ELECTRIC FIELDS IN MATTER
101 Dielectrics
10.2 The Moments of a Charge Distribution
10.5 The Potential and Field of a Dipole
10.4 The Torque and the Force
on a Dipole in an External Field
10.5 Atomic and Molecular Dipoles; Induced Dipole
Moments
10.6 Permanent Dipole Moments
CONTENTS ix
The Electric Field Caused by Polarized Matter
Another Look at the Capacitor
The Field of a Polarized Sphere
A Dielectric Sphere in a Uniform Field
The Field of a Charge in a Dielectric Medium,
and Gauss's Law
A Microscopic View of the Dielectric
Polarization in Changing Fields
The Bound-Charge Current
An Electromagnetic Wave in a Dielectric
Problems
CHAPTER 11
MAGNETIC FIELDS IN MATTER
How Various Substances Respond to a
Magnetic Field
The Absence of Magnetic "Charge"
The Field of a Current Loop
The Force on a Dipole in an External Field
Electric Currents in Atoms
Electron Spin and Magnetic Moment
Magnetic Susceptibility
The Magnetic Field Caused by
Magnetized Matter
The Field of a Permanent Magnet
Free Currents, and the Field H
Ferromagnetism
Problems
Appendix A:
A Short Review of Special Relativity
Appendix B:
Radiation by an Accelerated Charge
Appendix C:
Superconductivity
Appendix D:
Magnetic Resonance
Appendix E:
Exact Relations among SI and CGS Units
index