Dielectric

Dielectric is a material that is poor conductor of electricity, but an efficient supporter of electrostatic fields. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are allowed to fully develop an electric field, the material is a dielectric. The term is used to describe the electric insulation capability of a material.

Properties of Dielectrics

Dielectrics are defined by their behavior in an electric field, which can be influenced by the type of molecular structure they possess. The main properties of dielectrics are:

• Permittivity: This is the measure of a material's ability to store electrical energy in an electric field. The permittivity of a dielectric is often compared to the permittivity of a vacuum.

• Dielectric strength: This is the maximum electric field that a pure material can withstand under ideal conditions without breaking down (i.e., without experiencing failure of its insulating properties).

• Dielectric constant: This is the ratio of the permittivity of a substance to the permittivity of free space. It is a dimensionless quantity that is in general complex-valued; its real part is currently being discussed.

• Dielectric loss: This quantifies a dielectric material's inherent dissipation of electromagnetic energy (e.g. heat). It can be parameterized in terms of either the loss angle δ or the corresponding loss tangent tan δ.

Applications of Dielectrics

Dielectrics are used in a wide range of applications, including:

• Capacitors: Dielectrics are used in capacitors where they are sandwiched between the conducting plates. The dielectric increases the capacitor's charge capacity.

• Insulators: Dielectrics are used as insulators to stop the flow of current and prevent electrical shock.

• Transistors: In transistors, dielectrics are used to help control the amount of electricity that flows through the transistor.

See Also

• Electric field
• Electrostatics
• Permittivity
• Dielectric strength
• Dielectric constant
• Dielectric loss
• Capacitor
• Insulator
• Transistor

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  Capacitor schematic with dielectric
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  Dielectric model
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  Capacitor schematic with dielectric