Q. A cathode emits $1.8 \times 10^{14}$ electrons per second, when heated. When $400\ V$ is applied to anode all the emitted electrons reach the anode. The charge on electron is $1.6 \times 10^{- 19}C.$ The maximum anode current is
A) $2.7\ \mu A$
B) $29\ \mu A$
C) $72\mu A$
D) $29\ mA$
Explanation
(b) $i = \frac{Q}{t} = \frac{ne}{t} = 1.8 \times 10^{14} \times 1.6 \times 10^{- 19} = 28.8 \times 10^{- 6}A$
$= 29\ \mu A$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.