An ionization chamber with parallel conducting plates as anode and cathode has $5 imes 10^{7}$ electrons and the same number of singly-charged positive ions per $cm^{3}$. The electrons are moving at $0.4\ m/s$. The current density from anode to cathode is $4\mu A/m^{2}$. The velocity of positive ions moving towards cathode is

Question

An ionization chamber with parallel conducting plates as anode and cathode has $5 	imes 10^{7}$ electrons and the same number of singly-charged positive ions per $cm^{3}$. The electrons are moving at $0.4\ m/s$. The current density from anode to cathode is $4\mu A/m^{2}$. The velocity of positive ions moving towards cathode is

Dr. Abubacker · Accepted Answer

(d) Current density of drinking electrons $j = nev$
$n = 5 	imes 10^{7}\ cm^{- 3} = 5 	imes 10^{7} 	imes 10^{6}m^{- 3}$
$v = 0.4\ ms^{- 1},\ e = 1.6 	imes 10^{- 19}C \Rightarrow j = 3.2 	imes 10^{- 6}\ Am^{- 2}$
Current density of ions $= (4 - 3.2) 	imes 10^{- 6} = 0.8 	imes 10^{- 6}\frac{A}{m^{2}}$
This gives $v$ for ions $= 0.1\ ms^{- 1}$

Explanation

Reviewed by Dr. Abubacker

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