Electrical breakdown: Difference between revisions
From Glossary of Meteorology
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<div class="definition"><div class="short_definition">The sudden decrease of [[resistivity]] of a substance when the applied [[electric field strength]] rises above a certain threshold value (the substance's [[dielectric strength]]).</div><br/> <div class="paragraph">For air at normal [[pressures]] and [[temperatures]], experiment has shown that the [[breakdown]] process occurs at a [[field strength]] of about 3 × 10<sup>6</sup> V m<sup> | <div class="definition"><div class="short_definition">The sudden decrease of [[resistivity]] of a substance when the applied [[electric field strength]] rises above a certain threshold value (the substance's [[dielectric strength]]).</div><br/> <div class="paragraph">For air at normal [[pressures]] and [[temperatures]], experiment has shown that the [[breakdown]] process occurs at a [[field strength]] of about 3 × 10<sup>6</sup> V m<sup>-1</sup>. This value decreases approximately linearly with pressure, and is dependent upon [[humidity]] and traces of foreign gases. In the region of high field strength just ahead of an actively growing [[leader]] in a [[lightning stroke]], breakdown occurs in the form of a rapidly moving [[wave]] of sudden [[ionization]] ([[electron avalanche]]). The [[dielectric strength]] in a [[cloud]] of water drops is less than that in cloud-free humid air.</div><br/> </div> | ||
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Revision as of 15:08, 20 February 2012
electrical breakdown
The sudden decrease of resistivity of a substance when the applied electric field strength rises above a certain threshold value (the substance's dielectric strength).
For air at normal pressures and temperatures, experiment has shown that the breakdown process occurs at a field strength of about 3 × 106 V m-1. This value decreases approximately linearly with pressure, and is dependent upon humidity and traces of foreign gases. In the region of high field strength just ahead of an actively growing leader in a lightning stroke, breakdown occurs in the form of a rapidly moving wave of sudden ionization (electron avalanche). The dielectric strength in a cloud of water drops is less than that in cloud-free humid air.
