1.3.3 Electricity and magnetism
Name
Symbol
quantity of electricity,
electric charge
charge density
surface charge density
electric potential
electric potential
difference
electromotive force
electric field strength
electric flux
electric displacement
capacitance
permittivity
permittivity of vacuum
relative permittivity
dielectric polarization
(dipole moment per
volume)
electric susceptibility
electric dipole moment
electric current
Q
Definition
SI unit
Notes
C
-3
ρ
σ
V, φ
U, ∆V, ∆φ
ρ = Q/V
σ = Q/A
V = dW/dQ
U = V2 - V1
Cm
-2
Cm
-1
V, J C
V
E
E
Ψ
D
C
ε
ε0
εr
P
E = ∫(F/Q)⋅ ds
E = F/Q = -∇V
Ψ = ∫D⋅ dA
D = εE
C = Q/U
D = εE
1 2
ε0 = µ c
εr = ε/ε0
P = D - ε0E
V
-1
Vm
C
-2
Cm
-1
F, C V
-1
Fm
-1
Fm
1
-2
Cm
χe
p, µ
I, i
χe = εr - 1
p = ΣQiri
I = dQ/dt
1
Cm
A
(1)
(2)
(3)
(1)
dA is a vector element of area.
(2)
This quantity was formerly called dielectric constant.
(3)
When a dipole is composed of two point charages Q and -Q separated by a distance r,
the direction of the dipole vector is taken to be from the negative to the positive charge.
The opposite convention is sometimes used, but is to be discouraged. The dipole
moment of an ion depends on the choice of the origin.
Chapter 1 - 1
Name
Symbol
Definition
SI unit
Notes
electric current density
magnetic flux density,
magnetic induction
magnetic flux
magnetic field strength
permeability
permeability of vacuum
relative permeability
magnetization
(magnetic dipole
moment per volume)
magnetic susceptibility
molar magnetic
susceptibility
magnetic dipole
moment
electric resistance
conductance
loss angle
reactance
impedance,
(complex impedance)
admittance,
(complex admittance)
susceptance
resistivity
conductivity
self-inductance
mutual inductance
j, J
B
I = ∫j⋅ dA
F = Q v×B
Am
T
(1)
(4)
Φ
H
µ
µ0
µr
M
Φ = ∫B⋅ dA
B = µH
B = µH
-7
-1
µ0=4π×10 H m
µr = µ/µ0
M = B/µ0 - H A m-1
Wb
-1
Am
-2
-1
NA ,Hm
-1
Hm
1
(1)
χ, κ, (χm)
χm
χ = µr - 1
χm = Vmχ
1
3
-1
m mol
(5)
m, µ
Ep = -m⋅B
Am ,JT
R
G
δ
X
Z
R = U/I
G = 1/R
δ = φI - φU
X = (U/I) sinδ
Z = R + iX
Ω
S
1, rad
Ω
Ω
Y
Y = 1/Z
S
B
ρ
κ, γ, σ
L
M, L1 2
Y = G + iB
ρ = E/j
Ωm
-1
κ = 1/ρ
Sm
E = -L(dI/dt)
E1 = L1 2 (dI2/dt)
S
-2
2
-1
(6)
(6)
(7)
H
H
(4)
This quantity is sometimes loosely called magnetic field.
(5)
The symbol χm is sometimes used for magnetic susceptibility, but it should be reserved
for molar magnetic susceptibility.
(6)
In a material with reactance R = (U/I) cosδ, and G = R/(R + X ).
(7)
φI and φU are the phases of current and potential difference.
2
Chapter 1 - 2
2