Lakeshore Learning Materials 642 - Manual (Page 121)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual
Units for Magnetic Properties B-1
APPENDIX B
UNITS FOR MAGNETIC PROPERTIES
Table B-1. Conversion from CGS to SI Units
Quantity Symbol
Gaussian
& CGS emu
a
Conversion
Factor, C
b
SI &
Rationalized mks
c
Magnetic flux density,
Magnetic induction
B gauss (G) d 10 -4 tesla (T), Wb/m 2
Magnetic Flux φ maxwell (Mx), G•cm 2 10 -8
weber (Wb), volt
second (V•s)
Magnetic potential difference,
magnetomotive force
U, F gilbert (Gb) 10/4 π ampere (A)
Magnetic field strength,
magnetizing force
H oersted (Oe), e Gb/cm 10 3 /4 π A/m f
(Volume) magnetization g M emu/cm 3h 10 3 A/m
(Volume) magnetization 4 π M G 10 3 /4 π A/m
Magnetic polarization,
intensity of magnetization
J, I emu/cm 3 4 π × 10 -4 T, Wb/m 2i
(Mass) magnetization
σ , M emu/g
1
4 π × 10 -7
A•m 2 /kg
Wb•m/kg
Magnetic moment m emu, erg/G 10 -3
A•m 2 , joule per tesla
(J/T)
Magnetic dipole moment j emu, erg/G 4 π × 10 -10 Wb•m i
(Volume) susceptibility
χ , κ
dimensionless
emu/cm 3
—
(4 π ) 2 × 10 -7
Henry per meter
(H/m), Wb/(A•m)
(Mass) susceptibility χ
ρ
, κ
ρ
cm 3 /g, emu/g
4 π × 10 -3
(4 π )2 × 10 -10
m 3 /kg
H•m 2 /kg
(Molar) susceptibility
χ
mol
, κ
mol
cm 3 /mol, emu/mol
4 π × 10 -6
(4 π ) 2 × 10 -13
m 3 /mol
H•m 2 /mol
Permeability µ dimensionless 4 π × 10 -7 H/m, Wb/(A•m)
Relative permeability j µ
r
not defined — dimensionless
(Volume) energy density,
energy product k
W erg/cm 3 10 -1 J/m 3
Demagnetization factor D, N dimensionless 1/4 π dimensionless
NOTES:
a. Gaussian units and cgs emu are the same for magnetic properties. The defining relation is B = H + 4 π M.
b. Multiply a number in Gaussian units by C to convert it to SI (e.g. 1 G × 10 -4 T/G = 10 -4 T).
c. SI (Système International d'Unités) has been adopted by the National Bureau of Standards. Where two conversion factors are given, the upper one is
recognized under, or consistent with, SI and is based on the definition B = µ
0
(H + M), where to µ
0
= 4 π × 10 -7 H/m. The lower one is not recognized under SI
and is based on the definition B = µ
0
H + J, where the symbol I is often used in place of J.
d. 1 gauss = 10 5 gamma ( γ ).
e. Both oersted and gauss are expressed as cm -½ •g ½ •s -1 in terms of base units.
f. A/m was often expressed as "ampere-turn per meter" when used for magnetic field strength.
g. Magnetic moment per unit volume.
h. The designation "emu" is not a unit.
i.
Recognized under SI, even though based on the definition B = µ
0
H + J. See footnote c.
j. µ
r
= µ/µ
0
= 1 + χ , all in SI. µ
r
is equal to Gaussian µ.
k. B • H and µ
0
M • H have SI units J/m 3 , M • H and B • H/4 π have Gaussian units erg/cm 3 .
R.B. Goldfarb and F.R. Fickett, U.S. Department of Commerce, National Bureau of Standards, Bolder, Colorado 80303, March 1985, NBS Special Publication
696. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.