classical electrodynamics i - dept. of physics &...

Seoul National University Classical Electrodynamics I

Department of Physics & Astronomy Dai-Sik Kim

교제: John David Jackson

Dai-Sik Kim

Nano Optics Lab.

School of Physics and Astronomy

Seoul National University

Classical Electrodynamics I



Day 1

강의 Layout

• 시험 3번

• 숙제 2주마다 한번

• 시험/숙제/출석기타=50: 40: 10; 지정 좌석제

• 숙제 베끼면 0점 처리

Introduction and Survey

• Active participation in the lecture, such as asking many

questions, will be taken into consideration.

필기 안 하는 디카-핸카 족은 0점 처리



‘Jackson’은 살아있다



metal

Doped semiconductor

Oxide insulator

The most fundamentalMemory ‘device’; what happens when the insulator becomes less than1 nm thick?

epsilon=∞

epsilon=∞

epsilon=3

epsilon=∞

epsilon=∞

epsilon=3 ?



epsilo

n=∞

epsilo

n=∞

epsilo

n=3 ?

김태윤 + 박철환

We! need Maxwell-Schrodinger!!



Day 1

• My tardy adoption of the universally accepted SI system is a recognition that almost

all undergraduate physics texts, as well as engineering books at all levels, employ SI

units throughout. For many years, Ed Purcell and I had a pact to support each other

in the use of Gaussian units. Now I have betrayed him! Although this book is formally

dedicated to the memory of my father, I dedicate this third edition informally to the

memory of Edward Mills Purcell (1912-1997), a marvelous physicist with deep

understanding, a great teacher, and a wonderful man.

Jackson says:

t

BE

t

DJH

B

D

0

t

B

cE

t

D

cJ

cH

B

D

1

14

0

4


Yes1952년Nobel PrizeIn physicsFor NMR



P=cE (cgs)

P=e0cE (SI)EPED ee 0

EPED e 4



Day 1

It does not end here…

ee

BM

BHEPED

0

0 ; BqvqEF

e

BMBHEPED 4;4 B

c

vqqEF

0

J

t




In vacuum,

t

BE

t

EJB

B

E

000

0

0

e

e

t

B

cE

t

E

cJ

cB

B

E

1

14

0

4

1;][

][][;

][

][][

410;

4

110

22224

3

1

07

2

0

27

1

e

IT

MLk

IT

MLk

kck

cc

kk ;1

;1221



Day 1

There are an infinite number of possibilities for the choice of units. We

start with the Coulomb’s law and the Ampere’s law. Everything else

then follows.

Newtonr

qqkF ;

'21

??:

;/;'

2

2

1

2

k

kquestion

meterNewtond

IIkf

From observation of existing data, Maxwell when he derived his

famous equation, ‘realized’ that k1/k2=c2 in the year 1864.

2

2

1 ck

k




Day 1

][

][][;

][

][][

410;109

4

110

22224

3

1

072

9

0

271

IT

MLk

IT

MLk

kck

e

or cgs

221

1;1

ckk

1 m 떨어져 있는 1 C짜리 전하 사이의 힘 = 9x109 N

100 cm 떨어져 있는 ? statC짜리 전하 사이의 힘 = 9x109 N=9x1014 dyne

∴1 C=3x109 statC!!

Introduction and SurveyMKS



1. Let us measure the force between the two charges

2. Let us then discharge the charges.3. Let us measure the maximum force per length

between the two wires--- magnetic force due to the Ampere’s law applied to the currents carrying the discharge.

4. Now let us divide the electric force by the magnetic force--- this is the length dimension=L.

5. Now, multiply this quantity L by . What do we get?

6. Weber found that he gets something like

7. Hm…8. Can you tell what’s going on?9. How come it is not ??

2

r

2216 /105.4 sm

22216 /109 csm



Day 1

Magnetic field로 가보자

d

IIkf

'2 2

arbitraryd

IkB ;2 2

gausscgsforcαSI;forα

B;α

vqqEFworry.Don't;

d

IαkB

1

2 2




Day 1

t

E

k

kJkB

1

224

일반적인 단위에서의 막스웰 방정식

0;

10

441

221

Jt

Bvq

qEF

t

BEB

t

E

k

kJkBkE

Copyright ⓒ 2004 Pearson Education, Inc., publishing as Addison Wesley


dt

dE

kJ

kEdt

dJ

1

1

4

1

4;



Day 1

Quiz #1

1

)(2 AAA : Derive!

문제 2

0 A : Derive!




Day 1

][

][][;

][

][][

410;

4

110

22224

3

1

07

2

0

27

1

IT

MLk

IT

MLk

kck

e

or

221

1;1

ckk

3.

MKS

CGS

Examine MKS vs cgs; using 1 meter=100 centimeter,

Show that 1 C=3,000,000,000 statCoulomb




Day 1

t

E

k

kJ

c

kB

1

224

4. We are all hopefully familiar with how Maxwell derived his famous displacement

current equation as shown in the picture below. Please derive the generalized

Maxwell-Ampere equation:

Copyright ⓒ 2004 Pearson Education, Inc., publishing as Addison Wesley




1. Let us invent an inverse SI-MKS unit, whereby =1; 1 2

1;k c k

c

. Now, let us define a

unit charge invCoulomb and unit current invAmpere. A) Show that 1 invCoulomb=1/ 30

Coulomb; 1 invAmpere=1/ 30 Amp. B) What would be invV in V? C) Apply Ohm’s law to

show that 301 inv . D) Apply generalized Ampere’s law JkB

24 to an

infinitely long wire to show that 1 invTesla= 30 Tesla.

5



Day 1

t

BEB

t

E

k

kJkBkE

10

441

221

2

2

1

22

t

B

k

kB

6.

: Derive!


classical electrodynamics i - dept. of physics &...

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