Accelerated electron through a circular path

[odyssey4001]

Homework Statement

An Electron is accelerated through a potential difference of 5.0KV
(i) Find it's velocity.
(ii) It is then passed through a region of transverse magnetic field where it moves in a circular path of radius 0.20m. Find the magnititude of the field.
(iii) Find the time taken to for the electron to complete one rotation.

Homework Equations

For (iii)
Rotational KE = ½ Iw2
max velocity = 3x10^(7)
Magnitude of the field = 8.52x10^(-4)
potential difference = 5.0kV
radius = 0.20m
t = ?

The Attempt at a Solution

(i) I got 3x10^(7)
(ii) I got 8.52x10^(-4)
(iii) I'm really not sure how to approach this question any hints in the right direction would be great.

 

[graphene]

the magnetic field does not change the speed of the electron.
so its velocity would be what u calculated in (i).

then t = 2*pi*r/v.
as simple as that.