1. This document lists formulas related to electrostatics including: 2. Quantization of electric charge, Coulomb's law, electric field due to point charges, dipoles, and conductors. 3. It also includes formulas for electric potential, capacitance, work and energy related to electrostatic systems, and forces between charged plates.

1. Shahjahan-electrostatics-formula…
Shahjahan-electrostatics-formula
SL.
NO.
quantities FORMULA (RELATIONS ) Electrostatics
1 Quantisationof Elect.Charges(Q)
on a body
Q = n.e
n isIntegral Number,e ischarge on electron
1.6 X 10-19
C
2 Electrostaticforce constant 1/(4πϵ₀) value : 9 x 109
Nm2
C-2
3 Permittivity ϵ₀ 8.85 x 10-12
C2
N-1
m-2
4
Coulumb'sLaw F = q1q2/4πε₀r²
q1 and q2 are two chargesplacedat distance
r.
5 Forceson twocharges F12 = - F21 Directionof F isalongr.
6
DielectricConstant K = ε/ε₀ = εr
ε is absolute permittivityof medium, ε₀ is permittivity
of free space, εr is relative permittivity.
7
ElectricFieldata point E = F/q
F isforce experiencedbythe testcharge q at
a point.E is called fieldintensityatthat point
Force withrespectto field F = q.E
8 Electricfielddue tosource charge
Q at distance r
E = Q/(4πε₀r²) Directionof E is alongr.
9 ElectricFielddue todipole ona
pointon axial line
E = 2P/(4πε₀r³)
P isdipole moment,risdistance from centre
of dipole onaxial line.
10 ElectricFielddue todipole ona
pointon equitorialline
E = P/(4πε₀r³)
P isdipole moment,risdistance from centre
of dipole onequitorial line.
11 Electric Field due to dipoleatany
general point, atdistancer making
angleθ with P ⃗
E =
P√I(3cos²θ+1)/4πε₀r³
r is distanceof pointfrom midpointof dipole, θ is
anglebetween direction of r and dipolemoment P
E makesangle α withr then tan α =
1
2
tanθ
α isangle betweenresultantfieldand
directionof r, θ isangle betweenrandP
12 E atany pointon the axis of a
uniformly charged ringat distancer
qr/4πε₀(r²+a²)³⁄²
13 Torque on a dipole keptin
ElectricField
τ = PESinθ
or τ = Px E
P is dipolemoment, E is electric field,Direction of
Torque is normal to plain containingP and E
14 Work done forrotatingdipole by
angle θ
W = PE(1- Cosθ) P isdipole moment.Eiselectricfield
15 Potential Energy of dipolein
equilibriumcondition when P is
alongE.
U = - PE P isdipole moment.Eiselectricfield
16 Potential energyof dipole at90
degree toE
Zero
17 Potential energy of dipoleat 180 0 U = + PE P isdipole moment.Eiselectricfield
18 ElectricFlux φE φE= E.S = ∫E.ds
19
gausstheorem φE= ∮〖E.ds〗 = q/ε₀
Flux linkedtoaclosedsurface isq/ε₀times
the charge enclosedinit.
20 Fielddue toinfinite longstraight
chargedconductor
λ/2πϵ₀r
λ is linearcharge densityinthe conductor,ris
the perpendiculardistance.
21 Electricfielddue toinfinite plane
sheetof charge
σ /2ϵ₀
σ is areal charge density.Independentof
distance
22 Withintwoparallal sheetsof σ /ϵ₀ Outside,fieldiszero

2. Shahjahan-electrostatics-formula…
opposite charges
23 Withintwoparallal sheetsof
similarcharges
zero Outside,fieldisσ/ϵ₀
24 Electricfielddue tospherical
shell, outside shell
E = q/(4πε₀r²) q ischarge on shell,rdistance fromcentre.
25 Electricfieldonthe surface of
spherical shell.
E = q/(4πε₀R²) R is radiusof shell
26 Electric field inside spherical shell. Zero
27 Electric field insidethe sphere of
charge distributed uniformly all over
the volume .
E = rρ/3Є
r is radiusof sphere, ρ is volumetric charge
density, is permittivity of medium
28 Potential due tocharge Q at
distance r
V = Q/(4πε₀r) Potential ischaracteristicof thatlocation
29 Potential Energywithcharge q
keptat a pointwithpotentialV
U = qV = Qq/(4πε₀r)
Potential Energyisthatof the system
containingQand q.
30 Work done for in moving a chargeq
through a potential difference of V
W = q(V2-V1) V = (v2 -v1)
Energyof systemof twocharges U = q1q2/(4πε₀r)
31
Relationof E andV E = - dv/dr dv is potential difference between two points at
distancer where r and E are in the same direction.
32 Relationof E andV and θ E Cosθ = - dv/dr where θis angle betweendrandE
33 Potential atinfinity /inearth Zero
34 Electric Potential due to dipoleon a
point on axial line
V = P/(4πε₀r²)
P isdipole momentum,risdistance from
centre of dipole
35 Electric Potential due to dipoleon a
point on equitorial line
Zero
36
ElectricPotential due todipole at
any general point,
V = P cosθ / 4πε₀ (r2- a2
cos²θ)
P isdipole momentum,risdistance from
centre of dipole,aishalf lengthof dipole, is
angle betweenrandP
37 Work done in moving a charge
between two points of an
equipotential surface
Zero
38 Capacitance of a spherical
conductor
4πε₀R R is radiusof the sphere
39
Capacitance of a parallal plate
capacitor
ε₀kA/d
A is area of each plate, d is distancebetween
them, k is dilectric constantof the medium
between plates.
40
DielectricConstant k = C / C₀
Cis capacitancewith medium within plates,and C₀
is capacitancein free space.
41 Capacitance of a spherical
capacitor.
C = 4πε₀rarb/(ra-rb) ra and rb are radius of internal and external
spherical shells
42 Equivalentcapacitance for
Capacitorsinparallal
C = c1 + c2 +c3….
Cisequivalentcapacitance,c1,c2 are
capacitnce of the capacitorsjointtogether.
43 Equivalentcapacitance for
Capacitorsin series
1/C = 1/c1 + 1/c2 + 1/c3
. . .
44 Charge,capacitance,Potential
Difference
C = q/V
q ischarge onthe plate of capacitor andV is
Potential Difference betweenthe plates.
45
Energystoredincapacitor ½cv2
, ½qv, ½q2
/c
q ischarge, c is capacitance,vis Pot.
Difference

3. Shahjahan-electrostatics-formula…
46 CommonPotential V=C1V1+C2V2)/C1+C2
47 Energylossinconnecting
1
2
C₁C₂
C1+C₂
(V1-V2)2
c1 at v1 is connectedtoc2 at v2
48 C withdielectricslab inserted ε₀kA/d-t(1-1/k) t is thicknessof dielectricslabof constantk,
49 C withmetal plate inserted ε₀kA/(d-t) t is thicknessof metal plate inserted,
50 Force of attraction between plates ½q2
/ε₀A, ½ε₀E2
A q ischarge on plate,A isarea, E Elect.Field.