10.8: Capacitors

Describe the physical properties of a parallel plate capacitor.

A parallel-plate capacitor consists of two separated parallel conducting surfaces that can hold equal amounts of charge with opposite signs when placed in a circuit

Capacitance relates the magnitude of the charge stored on each plate to the electric potential difference created by the separation of those charges.

The capacitance of a capacitor depends only on the physical properties of the capacitor, such as the capacitor’s shape and the material used to separate the plates.

The capacitance of a parallel plate capacitor is proportional to the area of one of its plates and inversely proportional to the separation between its plates. The constant of proportionality is the product of the dielectric constant of the material between the plates and the electric permittivity of free space .

The electric field between two charged parallel plates with uniformly distributed electric charge, such as in a parallel plate capacitor, is constant in both magnitude and direction, except near the edges of the plates.

• The magnitude of the electric field between two charged parallel plates can be described with the equation

• A charged particle between two oppositely charged plates undergoes constant acceleration and therefore shares characteristics with the projectile motion of an object with mass in the gravitational field near Earth’s surface

The electric potential energy stored in a capacitor is equal to the work done by an external force to separate that amount of charge on the capacitor.

The electric potential energy stored in a capacitor is described by the equation