A beam of electrons is accelerated through a potential difference `V`. It is then passed normally through a uniform magnetic field where it moves in a circle of radius `r`. It would have moved in a circle of radius `2r` if it were initially accelarated through a potential difference

Options

A. `sqrt(2) V`
B. `2 V`
C. `2sqrt(2) V`
D. `4 V`

Answer

D

Explanation

`r = (sqrt(2m q V))/(Bq) rArr r prop sqrt(V)`
` (2r)/(r ) = sqrt((V')/(V)) rArr V' = 4 V`