The Physics Factbook
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
|Young, D. Hugh. University Physics, Eighth Edition. Addison-Wesley, 1992: 702.||"The dielectric strength of dry air is about 3 × 106 V [sic]. The values of dielectric strength of common insulating materials are given. Note that the values are all substantially greater than that for air."||> 3 × 106 V/m|
|Constricting a Capacitor. DeAnza College Website, Physical Sciences, Math., & Engineering Division||"If the dielectric strength of the wax paper is 40 × 106, to what maximum voltage could your capacitor be charged?"||4 × 107 V/m|
|Shelton, Christopher. Electrical Installations. Nelson Thornes, 2004.||"Listed (below) is a selection of examples that you will find in general use. Values are in kilovolts (thousands of volts) per millimeter thickness … Waxed Paper (used in low frequencies): 40 - 60"||4.0 × 107–6.0 × 107 V/m|
|Gray, Thomas. Smithsonian Physical Tables. City of Washington: Smithsonian Institute, 1903: 245.||"Dielectric strength of Different Substances, in Kilovolts...paraffined paper: 360"||3.6 × 107 V/m|
|Electrostatics Notes. Roy Mech Website for Engineers.||"Typical dielectric strength values are provided below:
Paraffin -Waxed Paper: 40 - 60 (MV/m)"
|4.0 × 107–6.0 × 107 V/m|
A charged object’s behavior depends on whether the object is made up of conducting or insulating materials. Conducting materials (like water) are ones that permit a free flow of electrons, while insulating, or dielectric, materials (the chief focus of this article) try to oppose that same flow.
While dielectric materials are made of atoms with tightly-bound electrons that resist the passage of current, they cannot withstand infinite amounts of voltage. Thus, once a specific potential difference is applied, their electrons will be ripped loose from their orbits and will crash into more molecules, liberating even more electrons. A current will be forced through the insulating material, causing it to breakdown. As a result, most solid dielectrics will be gravely damaged (or even destroyed), while liquid and gas dielectrics may still retain their previous insulating properties.
The voltage at which dielectric breakdown occurs determines a material’s dielectric strength (the maximum electric field strength that a material could withstand without loosing its insulating properties). This essential property also depends on the insulator’s shape and dimensions, the temperature of the medium surrounding the insulator, the electrodes used to apply the voltage and the duration of that applied voltage.
The dielectric strength of waxed paper is (on average) somewhere between 30 MV/m (mega or million volts per meter) and 60 MV/m. However, it can stray from that range, depending on the factors mentioned above.
Dasha Mulyukova -- 2007
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