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Electrostatics formulas
Electrostatic force
Coulomb's Law
F = kq1q2/r2
where k=1/4πεo=9x109Nm2C-2
εo = 8.85x10-12C2m-2N-1
See a solved example at Buzztutor.comVector notation
Electrostatic field
Electric field due to a point charge
E = F/qo = kq/r2 N/C
See a solved example at Buzztutor.comE due to circular loop of charge (radius r) at a distance x from the center
Electric dipole
Dipole moment
Cm
Electric field at an axial point of a dipole
Electric field at an equatorial point of a dipole
Torque acting on a dipole in a uniform electric field
Potential energy of a dipole in a uniform electric field
Electrostatic potential
Electrostatic potential difference
Potential due to a point charge
Potential at an axial point of a dipole
if 
then 
Potential at an equatorial point of a dipole
Relation between electrostatic field and potential gradient
Electric field = negative of the potential gradient
Electrostatic potential energy
Electrostatic potential energy of two point charges
Gauss' theorem
Electric flux
Gauss' theorem
Definition: Electric flux ϕ through any closed surface is 1/εo times the net charge Q enclosed by the surface.
Electric field E due to infinitely long straight wire (a line charge)
Electric field E due to thin infinite plane sheet of charge
Electric field between two thin infinite plane parallel sheets of charge
Electric field due to uniformly charged spherical shell
for r > R
for r < R
for r = R
Capacitance
Farad 1F = 1 C/V
Isolated spherical conductor
Parallel plate capacitor
or 
where
and k is dielectric constant
Capacitors in series
Capacitors in parallel
Energy stored in a capacitor
Energy density 
Common potential
C with conducting slab between the two plates
where t is thickness of slab [t < d]
C with dielectric slab between the two plates
where k is the dielectric constant