A charge q 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. Then potential difference required to move it in a circle of radius 2 r is

Options

A. 2V
B. 4V
C. 1V
D. 3V

Answer

B

Explanation

Radius of circular path : r = `sqrt(2mqV)/(qB)`
`rpropsqrtV` where B is constant
or `Vpropr^(2)`
`V_(2)/V_(1)=(r_(2)/r_(1))^(2)`
`V_(2)/V=((2r)/r)^(2)4rArrV_(2)=4V`