Capacitance and Dielectrics - Vocabulary flashcards

Vocabulary flashcards covering key concepts from capacitance, dielectric materials, and energy storage in capacitors.

Capacitance

The ability of a system to store electric charge per unit voltage; for a capacitor, C = Q/ΔV; unit: farad (F).

Farad (F)

The SI unit of capacitance; 1 F = 1 C/V.

Dielectric

An insulating material between capacitor plates that increases capacitance by reducing the electric field; characterized by its dielectric constant κ.

Dielectric constant (κ)

A dimensionless factor that scales a medium's permittivity relative to vacuum; κ = ε/ε0; used to compute C = κ ε0 A / d.

Permittivity (ε)

ε = ε0 κ; ε0 is the vacuum permittivity, ε is the medium's absolute permittivity (F/m).

Parallel-plate capacitor

A capacitor with two large, flat plates separated by a dielectric; C = ε A / d; E = ΔV/d.

Electric field (E) in a capacitor

The field between plates given by E = ΔV/d or E = σ/ε = Q/(ε A).

Potential difference (ΔV)

The voltage difference between the plates; ΔV = E d.

Charge (Q)

Electric charge stored on a capacitor plate; Q = C ΔV.

Energy stored in a capacitor

Electric potential energy due to charge separation; U_C = 1/2 Q ΔV = 1/2 C ΔV^2.

Energy density of the electric field

Energy per unit volume stored in the field; u_E = (1/2) ε E^2.

Dielectric insertion effect

Inserting a dielectric reduces the field for a given Q and increases capacitance by κ: C = κ C0; ΔV decreases while Q stays the same.

Vacuum permittivity (ε0)

Permittivity of free space, approx. 8.85 × 10^-12 F/m.

Capacitance without dielectric (C0)

Capacitance of a setup with no dielectric present; becomes C = κ C0 when a dielectric with κ is inserted.

Equipotential surface

A surface where the electric potential is constant; the electric field is perpendicular to equipotential surfaces.