Electrostatics Question 780
Question: An electron having charge e and mass m starts from the lower plate of two metallic plates separated by a distance d. If the potential difference between the plates is V, the time taken by the electron to reach the upper plate is given charge on C is
Options:
A) $ \sqrt{\frac{2md^{2}}{eV}} $
B) $ \sqrt{\frac{md^{2}}{eV}} $
C) $ \sqrt{\frac{md^{2}}{2eV}} $
D) $ \frac{2md^{2}}{eV} $
Show Answer
Answer:
Correct Answer: A
Solution:
[a] $ E=\frac{V}{d},F=eE=eV/d $
$ a=\frac{F}{m}=\frac{eV}{md} $
$ d=\frac{1}{2}at^{2}\text{ or }t=\sqrt{\frac{2d}{a}} $
$ \text{or }t=\sqrt{\frac{2dmd}{eV}}=\sqrt{\frac{2md^{2}}{eV}} $
