
Gaussian CGS 
SI 
Units and 


Charge 
2.997 92 ´ 10^{9} esu 
= 1 C = 1 A s 
Potential 
(1/299.792) statvolt 
= 1 V = 1 J C^{–1} 
Magnetic field 
10^{4} gauss = 10^{4} dyne/esu 
= 1 T = 1 N A^{–1 }m^{–1} 
Electron charge 
e = 4.803 204 ´ 10^{–10} esu 
= 1.602 176 ´ 10^{–19} C 
Lorentz force 
_{} 
_{} 
Maxwell equations 
_{} _{} _{} _{} 
_{} _{} _{} _{} 
Linear media 
_{} 
_{} 
Permittivity of free space 
_{} 
_{} 
Permeability of free space 
_{} 
_{} 
Fields from potentials 
_{} _{} 
_{} _{} 
Static
potentials 
_{} _{} 
_{} _{} 
Relativistic 
_{} _{} _{} _{} 
_{} _{} _{} _{} 
_{}_{} _{} 
Impedances (SI units)
r = resistivity at room temperature in 10^{–8} W m:
~ 1.7 for Cu ~ 5.5 for W
~ 2.4 for Au ~ 73 for SS 304
~ 2.8 for Al ~ 100 for Nichrome
(Al alloys may have
double this value.)
For alternating currents, instantaneous current I, voltage V, angular frequency w:
_{} .
Impedance of selfinductance L: Z = jwL .
Impedance of capacitance C: Z = 1/jwC .
Impedance of free space: _{} .
Highfrequency surface impedance of a good conductor:
_{} , where d = effective skin depth ;
_{} for Cu .
Capacitance _{} and inductance _{} per unit length (SI units)
Flat rectangular plates of width w, separated by d << w with linear medium (e, m) between:
_{} ;
_{} = 2 to 6 for plastics; 4 to 8 for porcelain, glasses;
_{}
Coaxial cable of inner radius r_{1}, outer radius r_{2}:
_{} .
Transmission lines (no loss):
Impedance: _{} .
Velocity: _{} .
Motion of charged particles in a uniform, static magnetic field
The path of motion of a charged particle of momentum p is a helix of constant radius R and constant pitch angle l, with the axis of the helix along B:
_{} ,
where the charge q is in units of the electronic charge. The angular velocity about the axis of the helix is
_{} ,
where E is the energy of the particle.
This section was adapted, with permission, from the 1999 web edition of the Review of Particle Physics (http://pdg. lbl.gov). See J. D. Jackson, Classical Electrodynamics, 2d ed. (John Wiley & Sons, New York, 1975) for more formulas and details. A PDF version of this table is also available.