C26 - Capacitance & Dielectrics

capacitance

• The charge that a capacitor can have at a fixed voltage

• Farads (F = 1 C/V)

*Q ∝ C∆V

capacitance (isolated charged sphere)

capacitance (parallel plates)

capacitors in parallel

C_eq = C₁ + C₂ + C₃ + ^{. . .}

capacitors in series

C_eq = (1/C₁ + 1/C₂ + 1/C₃ + ^{. . .})^-1

potential energy in a charged capacitor

energy density in an E-field

capacitance (w/ dielectric)

C = κC₀

κ = ∆V₀/∆V

dielectric strength

maximum field magnitude a dielectric can take w/o discharge

capacitor types

• IC chip

• curled metal foil + paper

• parallel plates & silicone oil

  • high voltage

• electrolytic capacitor

  • high capacitance

  • non-reversible

• variable capacitor

dipole moment

p ≡ 2aq

• 2a = distance

• q = charge of one dipole side

• vector: - → +

torque (dipole in an E-field)

potential energy (dipole in an E-field)

induced charge density on dielectric