Electric Charges and Fields

 

Key Equations

Coulomb’s law	F⃗ 12(r)=14πε0q1q2r212rˆ12
Superposition of electric forces	F⃗ (r)=14πε0Q∑i=1Nqir2irˆi
Electric force due to an electric field	F⃗ =QE⃗
Electric field at point P	E⃗ (P)≡14πε0∑i=1Nqir2irˆi
Field of an infinite wire	E⃗ (z)=14πε02λzkˆ
Field of an infinite plane	E⃗ =σ2ε0kˆ
Dipole moment	p⃗ ≡qd⃗
Torque on dipole in external E-field	τ⃗ =p⃗ ×E⃗