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Electrictiy
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SI unit for Current
Ampere (A); 1 ampere=1 coulomb per sec=1 c/s
Current Density
(J)=I/A=n
l
lv
d
=(A/m
2
)
Conductivity (rho)
rho=n
l
l
2
r/m
Electron current
i
e
=N
e
/(delta) t where N
e
=#electons
Electron Current in Wire
ie=n
e
Av
d
with SI unit s
-1
Electron Drift Speed
v
d
= (e (gamma) /m) E
Energy Density
u
E
=u
c
/A
d
=(Epsilon not)/2 x E
2
units (J/m
3
)
Dielectric- insulator inside a capacitor
Kappa==(Epsilon not)/E
Potential Difference w/in Dielectric
(delta) V
c
=((delta) Vc)
0
/Kappa
Capacitance
C=Q/(delta) Vc = (epsilon not x A) / d
Charge on Capacitor
Q=C delta V
o
Parallel Capacitor
C
eq
=C
1
+C
2
+C
3
=...
Greate than single
Series Capacitor
C
eq
=(1/C
1
+1/C
2
+1/C
3
+...)
-1
Less than single
Energy stored in capacitor
U
c
=Q
2
/2C = 1/2 C(deltaV
c
)
2
= epsilon not/2 (A
d
) E
2
Capacitance
Farad=F
Potential Difference
delta V = V
f
-V
i
= - (from i to f) E X ds
Potential (electric field comp in s dir)
E
s
=- dV/ds
Kirchhoff's Loop-sum of all potential differences in a loop/closed path
delta V
loop
=sigma ( delta V)= 0
Capacitance
C= Q/detla V
c
=Epsilon not x A / d
SI unit= farad
Author
Anonymous
ID
92480
Card Set
Electrictiy
Description
electricity physics formula
Updated
2011-06-30T03:35:45Z
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