Capacitance:

Capacitance is the ability to store an electrical charge.  A Capacitance is equal to the amount of charge which could be stored divided through the applied voltage, as display in Equation (3-7).

C   =    Q/ V                                                                          (3-7)

where

C   =    capacitance (F)

Q   =   amount of charge (C)

V   =    voltage (V)

The unit of capacitance is the F (farad).  A farad is the capacitance which will store one coulomb of charge whenever one volt is applied across the plates of the capacitor.

The dielectric constant (K) declares the ability of the dielectric to store electrical energy.  Air is used as a reference and is provided a dielectric constant of 1.  Thus, the dielectric constant is unitless.  A few other dielectric materials are paper, teflon, mica, bakelite, and ceramic.

A capacitance of a capacitor depends on three things.

1. Area of conductor plates

2. Separation between the plates

3. Dielectric constant of insulation material

In the Equation (3-8) describe the formula to search the capacitance of a capacitor along with two parallel plates.

C = K (A/d)  (8.85 x 10^-12)                                            (3-8)

where

C  = capacitance

K = dielectric constant

A = area

d = distance among the plates

8.85 x 10^-12 = constant of proportionality

Example:   Find the capacitance of a capacitor that stores 8 C of charge at 4 V.

C =Q/ V

C = 8/4

C =2F