Electrostatics — One-Page Revision Card — Summary

Charge: q = ne; e = $1.6 \times 10^{-19}$ C; conserved + quantized + additive
Coulomb: F = kq_{1}q_{2}/ $r^{2}$ ; k = $9 \times 10^{9}$ ; ε_{0} = $8.85 \times 10^{-12}$ ; [F] = [M $LT^{-2}$ ]
Field: E = kQ/ $r^{2}$ ; conductor inside = 0; insulator inside = kQr/ $R^{3}$ ; [E] = [M $LT^{-3}$$A^{-1}$ ]
Dipole: p = q·2l; E_axial = 2kp/ $r^{3}$ ; E_eq = kp/ $r^{3}$ ; ratio 2:1; V_eq = 0
Gauss: Φ = q_enc/ε_{0}; wire: λ/2πε_{0}r; plane: σ/2ε_{0}; sphere outside: kQ/ $r^{2}$
Potential: V = kQ/r; E = −dV/dr; equipotential W = 0; [V] = [ $ML^{2}$$T^{-3}$$A^{-1}$ ]
Capacitor: C = ε_{0}A/d; dielectric: KC; series: 1/C_eq = Σ1/Cᵢ; parallel: C_eq = ΣCᵢ
Energy: U = ½ $CV^{2}$ = $Q^{2}$ /2C; connected battery → U×K; disconnected → U÷K