Comparison between Townsend’s Theory and Streamer’s Theory

Sr.
No.

Townsend’s
Theory

Streamer’s
Theory

1.

Theory states, current growth occurs as a result of ionization
processes only.

Theory states, breakdown voltages were bound to depend on gas
pressure and geometry of the gap.

2.

This mechanism predicts a very diffused form of discharge.

This mechanism predicts discharges were found to be filamentary
irregular.

3.

Theory gives equation to prove Townsend’s criterion

Y [exp (αd) – 1] = 1

Theory gives equation

αd + ln (α/p) 14.5 ln
(E/p) + 1/2 ln(d/p)

this tells streamer’s criterion.

4.

Primary and secondary ionization causes avalanche breakdown.

The space charges fields play an important role in growth of avalanche
in corona a spark discharges in non-uniform field gaps.

5.

The mechanism predicts time lags of order of 10^-5 sec.

Breakdown occurs at very short times of the order of 10^-8 sec.

6.

Townsend’s mechanism operates for pd values below 1000 torr-cm and
gas pressures varying from 0.01 to 350 torr.

Streamer’s  mechanism operates
for higher values of pressure and higher value of pd.