Transcript Dynamics

Welcome to Physics 321
My Name is Brett Fadem
What is Electrodynamics
and How Does it Fit
Into The General Scheme
of Physics?
First, what is the distinction between
kinematics and dynamics?
The Distinction between Kinematics and Dynamics.
Kinematics
Kinematics is the study of motion without regard to the
cause. Kinesis is the Greek word for motion.
Dynamics
Dynamics is the study of the causes of motion.
Dunamis is the Greek word for power. We call the
Causes of motion, “forces.”
Source: The Dr. Physics Homepage. Please include
attributions in your work.
So, “electrodynamics” is the study of the
electric and magnetic causes of motion
(or, electric and magnetic forces).
But what part of physics studies the
resulting motion of objects
When acted upon by a force?
Mechanics!
Describe the force and mechanics will
tell you how things move.
What do you remember from classical mechanics?
1st Law
2nd Law
Newton’s Laws
Objects in motion, remain in motion. Objects
at rest remain at rest.


F  ma 

dp
m
dt
3rd Law


F12   F 21

d r
2
1
Relativistic Corrections?
dt
2
2
Special Relativity
Galilean Transformations
Lorentz Transformations
x   x  vt
x    ( x  vt )
y  y
y  y
z  z
z  z
t  t
t    ( t  vx


p  m v


p  mv
KE 
1
2
mv
2
KE  (  1) mc
 
2
c
2
)
1
1  (v c )
2
Classical Mechanics
(Newton: 1642-1727)
Special Relativity
(Einstein. 1905 was a big
year.)
Quantum Mechanics
(Bohr, Heisenberg,
Schrodinger, et al.)
Quantum Field Theory
(Dirac, Pauli, Feynman,
Schwinger, et al.)
The Four Forces to Which Mechanics is Applied:
1. Strong
2. Electromagnetic: complete theory in all 4 realms!
3. Weak
4. Gravitational
So, electrodynamics is the study of
the electromagnetic force, and
mechanics tells us how a system
will behave when subjected to that
force.
Unification?
Electricity
Magnetism
Electromagnetism
“QED”
Electroweak
Weak Force
Strong Force?
Gravity ??
Quantum Chromodynamics “QCD”
General Relativity
“In this Course, we are going to focus on classical
electromagnetism, that is, electromagnetism in the
context of classical physics.”
Comparison of Strength of Electromagnetic vs. Gravitational
Force
1
F EM 
q1 q 2
4  0 r
FG  G
mp=1.67x10-27 Kg
e =1.6x10-19 C
εo=8.85x10-12 C2/(Nm2)
G=6.67x10-11 (Nm2)/Kg2
2
m1m 2
r
2
1
e
2
4  o r
2
1
F EM

FG
G
mp
r
F EM
FG
2
1

e
4  o
Gm
2
 1 . 2  10
36
2
p
2
4  ( 8 . 85  10

( 6 . 67  10
 11
 12
C
(1 . 6  10
2
2
 19
C)
2
)
Nm

2
Nm
 27
2
)(
1
.
67

10
Kg
)
2
Kg
Electromagnetism is much stronger!
Maxwell’s Equations

 Q enc
 E  da 
 

E 


B  da  0
 
B 0
o
S

S



d
E  dl  
dt


B

d
l


I
o
enc

Gauss’s Law
o
 
E  

B
t
Faraday’s Law
 

  B   o J   o o
Ampere’s Law

E
t
For Each of Maxwell’s Equations,
you should have a simple picture
in your mind.
Gauss’s Law

 Q enc
 E  da 
S
o
Ampere’s Law


B

d
l


I
o
enc

Faraday’s Law



d
E  dl  
dt


   B  da
(i)
(ii)
Maxwell’s Equations in Vacuum

 
 
B
(iii)
E 0
E  
t
 
B 0
(iv)
 
  B   o o
Take the curl of the curl, etc.

B

 
  


2
  (  E )   (  E )   E    ( 
)
 t
  
E

(  B )    o o 2
t
t

 E 
2

1  E
2
c
2
t
2
And, you know who said,
“Let There Be Light!”

E
t
Introduction to Electrodynamics
Chapter 1
Vector Analysis
Chapter 2
Electrostatics
Chapter 3
Special Techniques
Vector Analysis
Differential Calculus
Integral Calculus
Curvilinear Coordinates
The Dirac Delta Function
The Theory of Vector Fields
The Electric Field
Divergence and Curl of
Electrostatic Fields
Electric Potential
Work and Energy in
Electrostatics
Conductors
Laplace’s Equation
The Method of Images
Separation of Variables
Multipole Expansions
Chapter 4
Electric Fields in Matter
Polarization
The Field of a Polarized Object
The Electric Displacement
Linear Dielectrics
Chapter 5
Magnetostatics
The Lorentz Force
Law
The Biot Savart Law
The Divergence and
Curl of B
Magnetic Vector
Potential
Chapter 6
Magnetic Fields in Matter
Magnetization
Field of a Magnetized Object
Auxiliary Field H
Linear and Nonlinear Media
Chapter 7
Electrodynamics
Electromotive Force
Electromagnetic Induction
Maxwell’s Equations