A particle of charge q and mass m is accelerated from rest
through a potential difference V, after which it encounters a
uniform magnetic field B perpendicular to its velocity v. If the
particle moves in a plane perpendicular to B,
(a) Find an expression for the radius of its circular path in
terms of q, V and B.
(b) If the particle is an electron, what must the potential
difference be so it describes a circular path of radius...