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Capacitance and Capacitors

Capacitance: Any volume (material) that has net charge in it produces electric potential aroun

d it (Gauss’ Law). The ratio of net charge in the volume to the potential of the volume (define poten

tial at infinitely far away is zero) is defined to be its capacitance (of holding charges in it):

The unit of capacitance is farad (F). 1 F = 1C/1V. The more charges the volume can hold at a given potential, the higher the capa

citance. Normal material has very small capacitance, pF to nF range.

Capacitor: The parallel plate capacitor.

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V

qc

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Capacitors

Cylindrical capacitor

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Capacitors

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Electric field energy stores in capacitors

Capacitors stores: Charges. Electric field. Electric field energy:

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Electric field energy

Electric field energy density uE

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Dielectrics

An Insulator (dielectric) in an electric field

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Dielectric constant k (kappa)

The dielectric constant k (kappa)

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Dielectric constant k (kappa)

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Electric field energy with dielectric materials

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Gauss’ Law with dielectric material

Gauss’ Law with a dielectric:

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Example problems

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Example problems

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Example problems