Capacitance (Physics)

Recall cards on capacitors and capacitance. Capacitors and capacitance: what a capacitor is and stores, its two-conductor construction, the definition C = Q/V, the farad and its name, the practical range, geometry dependence, the constant Q/V ratio, the parallel-plate result C = eps0*A/d, the permittivity of free space, the field E = sigma/eps0, and the spherical, isolated-sphere, and cylindrical capacitance formulas. Capacitors in series and parallel: the reciprocal-sum series rule, equal series charge, the smaller-than-smallest result, series voltage adding, the parallel sum rule, equal parallel voltage, the larger-than-largest result, parallel charge adding, and network reduction. Energy stored: field storage, the three energy forms U = 1/2 C V^2, U = Q^2/2C, U = 1/2 Q V, energy persisting after disconnection, the energy density u = 1/2 eps0 E^2, and the defibrillator. Capacitor with a dielectric: what a dielectric is, the dielectric constant kappa, kappa = 1 for vacuum and kappa > 1 otherwise, C = kappa*C_0, the constant-charge and voltage/energy drops on a disconnected capacitor, dielectric strength, and the stud finder. Molecular model of a dielectric: polar versus nonpolar molecules, alignment and induced dipoles, surface induced charge, the opposing induced field, E = E_0/kappa, and breakdown.