P2 - Ch23 - Capacitors

Capacitance

The charge stored per unit potential difference of a capacitor.

Time constant

For discharge of a capacitor C through a fixed resistor R, the time constant is RC. This is the time taken for the voltage/current/charge to reduce to 1/e of its initial value.

Dielectric

An electrically insulating material that can be inserted between the parallel plates of a capacitor, that increases the ability of the capacitor to store charge.

Relative permittivity

For a fixed p.d. across a parallel plate capacitor, the ratio of the charge stored with a dielectric to the charge stored without the dielectric.

Dielectric constant

The dielectric constant of a medium is: permittivity of the medium / permittivity of free space.