Start with two parallel plates connected to a battery. A potential is set up between them. If a conductor is placed between them, charge will flow.
If there is no conductor, static charge will be stored. If an insulating material called a dielectric (such as paper or paraffin) is placed between
them, a higher level of charge will be built up.
We call this a parallel plate capacitor.
When two plates are placed in this configuration, there is a proportional relationship between potential difference and total charge. We call this relationship Capacitance (C). The units for capacitance are Farads (F). C = Q/V. Typical capacitors in use in circuits today have capacitance in the microfarad (10 -6 F) to picofarad ( 10 - 12 F) range.
Recall that V = Ed. For two parallel plate capacitors, the electric field is uniform. If A is the area of the
is the distance between the plates, and e0is the permittivity of free space, then V
= Qd/e0A and C = e 0A/d.
Capacitance is directly proportional to the area of the plates and inversely proportional to the distance between the plates. In a graph of charge vs. potential, the slope of the line represents our capacitance and the area under the curve represents the energy stored.
In a graph of charge vs. potential, the slope of the line represents our capacitance and the area under the curve represents the energy stored.
The energy stored = 1/2 CV2. Units are Joules.
For more information on parallel plate capacitors and capacitance, click on the below links:
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