Lake Shore Model 647 Magnet Power Supply User’s Manual
Magnetic Units
A-1
APPENDIX A
UNITS FOR MAGNETIC PROPERTIES
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•cm2
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
x 10
-4
T,
Wb/m
2i
(Mass) magnetization
σ
, M
emu/g
1
4
π
x 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
x 10
-10
Wb•m
i
(Volume) susceptibility
χ
,
κ
dimensionless
emu/cm
3
-
(4
π
)
2
x 10
-7
Henry per meter
(H/m), Wb/(A•m)
(Mass) susceptibility
χ
ρ
,
κ
ρ
cm
3
/g, emu/g
4
π
x 10
-3
(4
π
)2 x 10
-10
m
3
/kg
H•m
2
/kg
(Molar) susceptibility
χ
mol
,
κ
mol
cm
3
/mol, emu/mol
4
π
x 10
-6
(4
π
)
2
x 10
-13
m
3
/mol
H•m
2
/mol
Permeability
µ dimensionless
4
π
x 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 x 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
x 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 uder SI, even thoug 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.
