Electrostatic and Capacitance

mass of electron

9.1 x 10^-31 kg

charge of electron

1.6 x 10^-19 C

Force

k q1q2 / r’2

k

9 x 10'9 nm'2/c'2

Êo value

8.85 x 10' -12 c'2/nm'2

Êr or k

Êm/Êo

f

qE

dimension of voltage

M'1 L'2 T'-3 A'-1

E

k q /r’2

p

2qa

E axial

k 2p / r’3

E equatorial

k p / r’3

torque

PE sintheta

stable torque

PE sin0 -0

max torque

PE sin90 -PE

unstable torque

PE sin180 -0

flux

E ds costheta

E ds costheta (gauss law)

q / Ê

E infinite wire

lamda / 2π Êo r

E infinite plane

sigma / 2π Êo

E for 2 planes

sigma / Êo

E outside shell

k q / r’2

E surface of shell

k q / R’2

E inside shell

0

Vb - Va

Wab / q

W

vq

V

k q / r

V axial

k p / r’2

V equatorial

0

V any point

k pcostheta /r’2

V outside shell

k q /r

V on the surface of shell

k q /R

V inside shell

k q / R

E (relation with V)

-dv /dr

U

k q1q2 / r

U (dipole)

— PE costheta

minimum and stable energy

— PE

minimum and stable U

-PE cos0 - -PE

maximum and unstable U

-PE cos180 - PE

polarisation

p = X E , dipole / vol

C

Q/V

C of sphere

4πÊor

C of parallel plate

ÊoA / d

C of parallel plate with dielectric slab

ÊoA / d-t + (t/k)

C of parallel plate with dielectric

k ÊoA / d

Energy

½ cv’2

Energy Density

½ Êo E’2