Question

What distance must an electron move in a uniform potential gradient 200 v/cm in order to gain Kinetic energy 3.2×10^-18 J?(e=-1.6×10^-19C , Me=9×10^-31kg)

Answer 1

We know that energy of `1\ eV =1.6xx10^-19\ J`
`=>3.2×10^-18\ J =(3.2×10^-18)/(1.6×10^-19)=20\ eV`

Given uniform potential gradient `V=200/(1/100)=2.0xx10^4\ Vm^-1`

KE gained is `2.0xx10^4\ eV` when it moves distance `= 1\ m`,
KE gained is `20\ eV` when it moves a distance `= 1/(2.0xx10^4)xx20`

`=>`Required distance `=10^-3\ m`