Electronic Devices Question 181
Question: Thermionic emission from a heated filament varies with its temperature T as
[CBSE PMT 1990; RPMT 2000; CPMT 2002]
Options:
A) $ {{T}^{-1}} $
B) $ T $
C) $ T^{2} $
D) $ {{T}^{3/2}} $
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Answer:
Correct Answer: C
Solution:
According to Richardson-Dushman equation, number of thermions emitted per sec per unit area
$ J=AT^{2}{{e}^{-W _{0}/kT}} $
Therefore $ J\propto T^{2} $
