Field Quantities
E
Electrical field intensity (V/m).
Defined as the electric force on a unit charge. Only vector needed in
discussing electrostatics (effects of stationary electric charge) in
free space.
D
Electric flux density or electric displacement (C/m2).
Useful in the study of electric field in material media.
B
Magnetic flux density (T, Tesla, V-sec/m2).
Magnetic force acting on a charge moving with a given velocity. Only
vector is needed in discussing magneto statics (effects of steady
electric currents) in free space.
H
Magnetic field intensity (A/m).
Useful in the study of magnetic field in material media.
Universal Constants in Free Space
c =
1
ε
0
μ
0
m/s
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaiaayk
W7cqGH9aqpcaaMc8+aaSaaaeaacaaIXaaabaWaaOaaaeaacqaH1oqz
daWgaaWcbaGaaGimaaqabaGccqaH8oqBdaWgaaWcbaGaaGimaaqaba
aabeaaaaGccaaMe8UaaeyBaiaab+cacaqGZbaaaa@4534@
Or,
ε
0
=
1
/
c
2
μ
0
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqyTdu2aaS
baaSqaaiaaicdaaeqaaOGaaGPaVlabg2da9iaaykW7caaIXaGaaGPa
Vlaac+cacaaMc8+aaeWaaeaacaWGJbWaaWbaaSqabeaacaaIYaaaaO
GaeqiVd02aaSbaaSqaaiaaicdaaeqaaaGccaGLOaGaayzkaaaaaa@4734@
≈
1
/
36
π
′
10
−
9
F/m
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyisISRaaG
PaVpaabmaabaGaaGymaiaaykW7caGGVaGaaGPaVlaaiodacaaI2aGa
eqiWdahacaGLOaGaayzkaaWaaWbaaSqabeaakiadacUHYaIOaaGaaG
PaVlaaigdacaaIWaWaaWbaaSqabeaacqGHsislcaaI5aaaaOGaaGjb
VlaabAeacaqGVaGaaeyBaaaa@4E74@
Where,
c
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaaaa@36DB@
Velocity of electromagnetic wave (including light).
c ≈
3
′
10
8
m/s
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaiaayk
W7cqGHijYUcaaMc8UabG4mayaafaGaaGymaiaaicdadaahaaWcbeqa
aiaaiIdaaaGccaaMe8UaaeyBaiaab+cacaqGZbaaaa@42FE@
ε
0
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqyTdu2aaS
baaSqaaiaaicdaaeqaaaaa@3880@
Permittivity of free space.
D =
ε
0
E
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiraiaayk
W7cqGH9aqpcaaMc8UaeqyTdu2aaSbaaSqaaiaaicdaaeqaaOGaamyr
aaaa@3E39@
μ
0
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiVd02aaS
baaSqaaiaaicdaaeqaaaaa@388F@
Permeability of free space.
H =
1 /
μ
0
B ,
μ
0
= 4
π
′
10
− 7
H/m
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamisaiaayk
W7cqGH9aqpcaaMc8+aaeWaaeaacaaIXaGaaGPaVlaac+cacaaMc8Ua
eqiVd02aaSbaaSqaaiaaicdaaeqaaaGccaGLOaGaayzkaaGaaGPaVl
aadkeacaGGSaGaaGzbVlabeY7aTnaaBaaaleaacaaIWaaabeaakiaa
ykW7cqGH9aqpcaaMc8UaaGinaiqbec8aWzaafaGaaGymaiaaicdada
ahaaWcbeqaaiabgkHiTiaaiEdaaaGccaaMe8Uaaeisaiaab+cacaqG
Tbaaaa@58BC@
ε
0
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqyTdu2aaS
baaSqaaiaaicdaaeqaaaaa@3880@
and
μ
0
MathType@MTEF@5@5@+=
feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr
4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9
vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x
fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiVd02aaS
baaSqaaiaaicdaaeqaaaaa@388F@
are not independent.