Parallel Plate Capacitor

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The capacitance of flat, parallel metallic plates of area A and separation d is given by the expression above where:

 = permittivity of space and
k = relative permittivity of the dielectric material between the plates.

k=1 for free space, k>1 for all media, approximately =1 for air.

The Farad, F, is the SI unit for capacitance, and from the definition of capacitance is seen to be equal to a Coulomb/Volt.

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 Capacitance = k x ε0 x area / separation

For parallel plates of area A = m2 and separation d = m,
with relative permittivity k= , the capacitance is

 C = μF = x10^ F = pF
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Capacitor Concepts

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Capacitance of Parallel Plates

The electric field between two large parallel plates is given by

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The voltage difference between the two plates can be expressed in terms of the work done on a positive test charge q when it moves from the positive to the negative plate.

It then follows from the definition of capacitance that

 Calculation Effect of dielectric What is the dielectric constant?
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Capacitor Concepts

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