Capacitor with a Dielectric

Michael Faraday

In 1837 found that capacitance increase by numerical factor 'k' with this instrument.

DIELECTRIC CONSTANT

Polarization in InsulatorsPositively charged species in insulators shift/rotate/align toward the negative electrode and negatively charged species shift/rotate/align towards the positive electrode; creating dipoles.

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Ionic polarization occurs in all ionic

solids: NaCl, MgO…

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Molecular polarization, occurs in all insulat ing

molecules; oils, polymers, H2O…

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Electron CloudElectron Cloud

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Electronic polarization, occurs in insulators

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Dielectric & Capacitors

What is Capacitor?

A device used to store charge.

OR

Two electrodes separated by a gap define a capacitor.

What is Capacitance?

The amount of charge that the capacitor can store (Q) is proportional to the

bias (V) times how good the capacitor is, the ‘capacitance’ (C).

The capacitance is related to the area of the plates (A), their separation (d), and

the Dielectric Constant (εεo) of the dielectric between the plates

Breakdown Voltage

Definition: The breakdown voltage

of an insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive.

Summary of Capacitor with a Dielectric

An insulating material which has the effect of increasing the capacitance of a vacuum-filled parallel plate capacitor, when it is inserted between its plates, is called a dielectric material, and the factor by which the capacitance is increased is called the dielectric constant of that material.