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Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
John David Jackson
Dai-Sik Kim
Nano Optics Lab.
School of Physics and Astronomy
Seoul National University
Classical Electrodynamics I
전기역학 1(김대식)
2012-20368
안대건010-8601-2444
2013-30117
이덕형 010-3684-0624 [email protected]
2012-23101
주상현 010-9086-3368 [email protected]
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
From Wikipedia, the free encyclopedia
Charles-
Augustin de
Coulomb
Michael
Faraday
André-
Marie
Ampère
James
Clerk
Maxwell
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
Concept of field: Maxwell on Faraday’s death: Faraday was a mathematician in his own way!
• The high place which we assign to Faraday in electromagnetic science may
appear to some inconsistent with the fact that electromagnetic science is an
exact science, and that in some of its branches it had already assumed a
mathematical form before the time of Faraday, whereas Faraday was not a
professed mathematician, and in his writings we find none of these
integrations of differential equations which are supposed to be of the very
essence of exact science. Open Poisson and Ampere, who went before him,
and you will find their pages full of symbols, not one of which Faraday
would have understood. It is admitted that Faraday made some great
discoveries, but if we put these aside, how can we rank his scientific method
so high without disparaging the mathematics of these eminent men?
• For instance, Faraday, in his mind’s eye, saw lines of forces traversing all
space where mathematicians saw centers of force attracting at a distance.
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
Faraday’s life
Michael Faraday was born in Newington Butts, near present-day Elephant and Castle in South
London, England. His family was extremely poor; his father, James Faraday, was a Yorkshire
blacksmith who suffered ill-health throughout his life.[2] After the most basic of school educations,
Faraday had to educate himself. At fourteen he became apprenticed to a local bookbinder and
bookseller George Riebau and, during his seven-year apprenticeship, he read many books, including
Isaac Watts' The Improvement of the Mind, the principles and suggestions contained therein he
enthusiastically implemented. He developed an interest in science and specifically electricity. In
particular, he was inspired by the book Conversations in Chemistry by Jane Marcet. [7]
At the age of twenty, in 1812, at the end of his apprenticeship, Faraday attended lectures by the
eminent English chemist and physicist Humphry Davy of the Royal Institution and Royal Society, and
John Tatum, founder of the City Philosophical Society. Many tickets for these lectures were given to
Faraday by William Dance (one of the founders of the Royal Philharmonic Society). Afterwards,
Faraday sent Davy a three hundred page book based on notes taken during the lectures. Davy's
reply was immediate, kind and favorable. When Davy damaged his eyesight in an accident with
nitrogen trichloride, he decided to employ Faraday as a secretary. When John Payne, one of the
Royal Institution's assistants, was sacked, the now Sir Humphry Davy was asked to find a
replacement. He appointed Faraday as Chemical Assistant at the Royal Institution on March 1 1813.
[2]
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
In the class-based English society of the time, Faraday was not considered a gentleman. When Davy
went on a long tour to the continent in 1813-5, his valet did not wish to go. Faraday was going as
Davy's scientific assistant, and was asked to act as Davy's valet until a replacement could be found in
Paris. Davy failed to find a replacement, and Faraday was forced to fill the role of valet as well as
assistant throughout the trip. Davy's wife, Jane Apreece, refused to treat Faraday as an equal (making
him travel outside the coach, eat with the servants, etc.) and generally made Faraday so miserable
that he contemplated returning to England alone and giving up science altogether. The trip did,
however, give him access to the European scientific elite and a host of stimulating ideas. [2]
His sponsor and mentor was John 'Mad Jack' Fuller, who created the Fullerian Professorship of
Chemistry at the Royal Institution.
Faraday was a devout Christian and a member of the small Sandemanian denomination, an offshoot
of the Church of Scotland. He later served two terms as an elder in the group's church.
Faraday married Sarah Barnard (1800-1879) on June 2, 1821, although they would never have
children. They met through attending the Sandemanian church.
He was elected a member of the Royal Society in 1824, appointed director of the laboratory in 1825;
and in 1833 he was appointed Fullerian professor of chemistry in the institution for life, without the
obligation to deliver lectures.
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
The concept of field: try to understand this without field concept
http://www.physics.uiowa.edu/~umallik/adventure/nov_06-04/inductance.gif
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 2Introduction and Survey
Concept of field
physics.bu.edu www.windows.ucar.edu
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
1. Introduction to ElectrostaticsDay 2
3
12
12
0
1
4 xx
xxqE
i i
ii
xx
xxqE
3
04
In general,
xdxdq 3
3
3
04
1
xx
xdxxxE
1.2 Electric Field
21 qq
3
12
12
0
21
2
12
21
0
21
4
ˆ
4 xx
xxqq
xx
xqqF
Coulomb’s Law
q2
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
? sdE
0 sdE
0
2
2
04
q
r
drqsdE
0insideq
sdE
1.3 Gauss’s Law
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
xdxx
xx
3
0
1
4
xdzxxz
yxxy
xxxx
xx
3
0
ˆ1
ˆ1
ˆ1
4
For now, before Faraday induction
,0
E
23
222222
1
zzyyxx
xx
zzyyxxx
23
222222
1
zzyyxx
yy
zzyyxxy
23
222222
1
zzyyxx
zz
zzyyxxz
0
t
BE
3
3
04
1
xx
xdxxx
E
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
0
3
insideq
xdE
xdxxdE 3
0
3 1
)(00
spacefreeinE
3
3
04
1
xx
xdxxxE
)(0
22
3
22
3
22
3
4
1
2
5222
2222
2
5222
2222
2
5222
2222
3
0
xxat
zzyyxx
zzzzyyxx
zzyyxx
yyzzyyxx
zzyyxx
xxzzyyxx
xxdz
E
y
E
x
EE zyx
Prove it.
pf)
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
33
xx
xx
xx
xx
Day 21. Introduction to Electrostatics
3
3
04
1
xx
xdxxxE
004
xd
x
da
a
x
sphere
2
2
0
1
4
xd
xx
xxx
3
3
04
xd
xx
xxx
sphere
3
3
04
a
'x
x
By divergence theorem
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
3
3
04
1
xx
xdxxxE
xxxx
412 The definition of δ-function
xxqx
xxatxx
xxatxx
xdxx
0
1
xd
xx
x
3
0
1
4
0
32
0
1
4
xxd
xx
x
due to the above result!!
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
* Dipole!
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
* Electric Dipole!
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
* Magnetic Dipole!
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
z
dx
q
zd
x
qx
ˆ2
4ˆ2
4 00
q
-q
x
qdp
2
d
2
d
Seoul National University Classical Electrodynamics I
Department of Physics & Astronomy Dai-Sik Kim
Day 21. Introduction to Electrostatics
?xf
...!3
1
2
1 3
3
32
2
2
dx
fd
dx
fd
dx
xdfxfxf
In one dimension,
In three dimension,
fxf
z
f
y
f
x
fxfxf zyx
...
zyxwhere ,,