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Dielectric

Dielectric. Materials affect the electric field. Conductors block it Insulators become polarized Polarized insulators decrease the field for the charge on the plates. Fields in Material. +. -. -. +. +. -. Insulators have higher permittivity than the vacuum.

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Dielectric

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  1. Dielectric

  2. Materials affect the electric field. Conductors block it Insulators become polarized Polarized insulators decrease the field for the charge on the plates. Fields in Material + - - + + -

  3. Insulators have higher permittivity than the vacuum. Relative permittivity is the ratio of the permittivity compared to the free permittivity of the vacuum. Materials used for their permittivity are dielectrics. Relative permittivity = dielectric constant Some dielectric constants (K): Vacuum 1.00000 Air 1.00054 Polyethylene 2.3 Paper 2-4 Mica 3-6 Glass 5-10 Body tissue 8 Ethanol 24 Water 80 Permittivity

  4. A point charge of 10 mC is surrounded by water with a dielectric constant of 80. Find the electric field at a distance of 20 cm. The formula for a point source charge is Using the values in the problem E = 28 kN/C. Factor of 80 times smaller than in vacuum Field Check

  5. A dielectric reduces the field for a give charge. A dielectric also increases the charge for a given field. The field is determined by the voltage and gap. Dielectrics increase capacitance. Capacitor Strength + - - + + -

  6. - - - - - + + + + + Cell Regulation • Water has a very high dielectric constant: 80. • Molecule naturally polarized • Fluid allows rearrangement • This allows very high charge storage across cell membranes.

  7. Shown below are capacitors Multilayer ceramic Ceramic disk Multilayer polyester Tubular ceramic Polystyrene Metalized polyester Aluminum electrolytic Capacitors generally use dielectrics to increase the capacitance. Capacitor Types next

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