Streamer Theory or Kanal Theory

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Streamer Theory or Kanal Theory

Q. Explain the streamer theory of breakdown in air at atmospheric pressure.

A narrow river of conducting particles.

  1. Stage when secondary avalanche (due to positive ions) has crossed.
  2. Streamer has crossed 1/2 the gap length.
  3. Gap has been bridged by a conducting channel i.e. Streamer.

Streamer Mechanism
Figure A

Streamer Theory or Kanal Theory
Figure B

  • The electric field produced (Ef) due to positive space charges at radius is given by 

Ef  = 5.27 x 107 [eαd /
(d/p)1/2] V /cm

Where d – Gap distance (cm) 

p – Gas pressure (torr)
a – Townsends primary ionisation coefficient
But still there are controversies between two theories and hence.

  • For pd value less than 1000 tort.cm uniform field use Townsend’s theory.
  • For pd values > 1000 torr. cm, non-uniform field, Streamer theory is used.

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