Definitions Glossary — Electrostatics — Notes | NoteTube

Term	Definition	Context / Key Value
Electric charge	Fundamental property of matter causing electromagnetic force	Unit: coulomb (C); e = $1.6 \times 10^{-19}$ C
Quantization of charge	Charge exists only in integer multiples of e	q = ne, n ∈ ℤ
Conservation of charge	Total charge of an isolated system remains constant	Holds in all physical processes
Coulomb's law	F = kq_{1}q_{2}/ $r^{2}$ between two point charges	k = $9 \times 10^{9}$ N $m^{2}$ $C^{-2}$
Permittivity of free space	ε_{0} = $8.85 \times 10^{-12}$ $C^{2}$ $N^{-1}$ $m^{-2}$ ; relates E field to charge	[ε_{0}] = [ $M^{-1}$$L^{-3}$$T^{4}$$A^{2}$ ]
Electric field	Force per unit positive test charge at a point	E = F/q_{0}; unit: N/C
Electric field lines	Imaginary lines showing direction of E; density ∝ field strength	Start on +q, end on −q; never cross
Superposition principle	Net force/field = vector sum of individual contributions	Applies to both force and field
Electric dipole	System of two equal, opposite charges ±q separated by 2l	p = q·2l; direction: −q to +q
Dipole moment	p = q·2l; vector from −q to +q	[p] = [ATL]; unit: C·m
Electric flux	Φ = ∮E·dA; total field lines through a surface	Unit: V·m or N $m^{2}$ $C^{-1}$
Gauss's law	Total flux through closed surface = q_enc/ε_{0}	Powerful tool for symmetric charge distributions
Electric potential	Work done per unit positive charge to bring it from ∞ to a point	V = kQ/r; unit: volt (V)
Equipotential surface	Surface on which potential is constant everywhere	E ⊥ equipotential surface; no work to move charge on it
Capacitance	Charge stored per unit voltage: C = Q/V	Unit: farad (F); depends only on geometry
Dielectric constant	K = C_dielectric/C_vacuum; dimensionless ratio	K ≥ 1; for vacuum K = 1
Energy stored in capacitor	U = ½ $CV^{2}$ = $Q^{2}$ /2C	Unit: joule (J)
Linear charge density (λ)	Charge per unit length	[λ] = [ $AL^{-1}$ T]; unit: C/m
Surface charge density (σ)	Charge per unit area	[σ] = [ $AL^{-2}$ T]; unit: C/ $m^{2}$
Volume charge density (ρ)	Charge per unit volume	[ρ] = [A $L^{-3}$ T]; unit: C/ $m^{3}$