Higher dielectric constant : better insulator

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Discussion Overview

The discussion revolves around the relationship between dielectric constant and electrical conductivity, particularly in the context of water as a dielectric material. Participants explore whether a higher dielectric constant correlates with better insulating properties, examining the properties of pure and impure water.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant asserts that a higher dielectric constant indicates better insulating properties, using water as an example.
  • Another participant corrects the dielectric constant of water, stating it is 80, not 8, and notes that impure water, such as seawater, is a good conductor.
  • A third participant emphasizes that dielectric constant does not determine insulating ability, arguing that electrical conductivity is the key factor, citing air as an example of a good insulator with a dielectric constant of unity.
  • This participant also explains the effects of high dielectric constants on light propagation and polarization, discussing how these properties contribute to the effectiveness of dielectrics in capacitors.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between dielectric constant and insulating properties, with no consensus reached on the implications of these properties for materials like water.

Contextual Notes

Participants highlight the distinction between dielectric constant and electrical conductivity, indicating that assumptions about these properties may vary based on the context of the materials discussed.

dharm0us
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Higher dielectric constant means better insulator.
Water has a dielectric constant of 8, which is enormous(according to Walter Lewin),
but it still is a very good conductor of electricity, why?
 
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1) The dielectric constant of pure water is 80, not 8.
2) impure water, especially seawater, is a good conductor (think electrolysis of hydrogen and oxygen).
 
Dielectric constant is not an indicator of being a good insulator. The electrical conductivity is what gives a material it's properties relating to being an insulator or conductor. Take a look at air, it has a dielectric constant of unity, yet it is a very good insulator.

A high dielectric constant will result in a slower propagation of light through the medium and it allows for polarization of the medium. The polarization is the ability for the molecules or atoms in the medium to slightly separate to become dipole moments in the presence of an applied electric field. This has the effect of lowering the apparent magnitude of the electric field, but the energy lost in the field is stored in the polarization of the material. This helps make a dielectric effective in improving capacitors since you can store energy in the polarizing of the dielectric as well as in the voltage induced by the stored charges.
 

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