Appendix C. Units

http://optics.hanyang.ac.kr/~shsong

Introduction to Electrodynamics, 4^rd Edition, David J. Griffiths 1. Vector analysis

2. Electrostatics

3. Special techniques 4. Electric fields in mater 5. Magnetostatics

6. Magnetic fields in matter 7. Electrodynamics

8. Conservation laws

9. Electromagnetic waves 10. Potentials and fields 11. Radiation

12. Electrodynamics and relativity

Introduction to Electrodynamics, 4^rd Edition, David J. Griffiths

Introduction

Review on Electromagnetics in the General Physics

Introduction to Electrodynamics, 4^rd Edition, David J. Griffiths

Appendix C. Units

SI unit (the Systeme International):

 meters (m), kilograms (kg), seconds (s), and charge in coulombs (C) Gaussian unit (the Gaussian system):

 centimeters (cm), grams (g), seconds (s), and charge in electrostatic units (esu)

Converting electrostatic equations from SI to Gaussian units is not difficult: just set

0

1 ( )

( )

4 q Gaussian C SI

 

 

9 9

1 C = 3 10  dyne cm   3 10 esu

esu =  dyne cm 

Units

One major virtue of the Gaussian system is that electric and magnetic fields have

the same dimensions.

In effect,

the magnetic field is "scaled up" by a factor of c.

This reveals more starkly the parallel structure of electricity and magnetism.

The Gaussian units eliminates the ₀and ₀ that spoil the symmetry in the SI formula.

Maxwell's Equations

D and H

Lorentz force law

Energy and Power

BASIC EQUATIONS OF ELECTRODYNAMICS in SI units

Auxiliary Fields

Potentials

Lorentz force law