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 by
.
A. `sqrt((2 m d^2)/(e V))`
B. `sqrt(( m d^2)/(e V))`
C. `sqrt(( m d^2)/(2 e V))`
D. `(2 m d^2)/( e V)`

Answer 1

Correct Answer - a
`E = V/d, F = eE = e V// d`
`a = (F)/(m) = (e V)/(m d)`
`d = (1)/(2) at^2` or `t = sqrt((2d)/A)`
or `t = sqrt((2 d m d)/(e V)) = sqrt((2 md^2)/(e V))`.