Current Electricity Charging Discharging Of Capacitors Question 152
Question: An ionization chamber with parallel conducting plates as anode and cathode has $ 5\times 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
[CBSE PMT 1992]
Options:
A) 0.4 m/s
B) 16 m/s
C) Zero
D) 0.1 m/s
Show Answer
Answer:
Correct Answer: D
Solution:
Current density of drifting electrons j = nev $ n=5\times 10^{7}c{{m}^{-3}}=5\times 10^{7}\times 10^{6}{{m}^{-3}} $ . $ v=0.4m{{s}^{-1}},,e=1.6\times {{10}^{-19}}C $
Therefore $ j=3.2\times {{10}^{-6}}A{{m}^{-2}} $ Current density of ions = (4 ? 3.2) ´ 10?6 = $ 0.8\times {{10}^{-6}}\frac{A}{m^{2}} $ This gives v for ions = 0.1 ms?1.
BETA
