In a velocity selector, the uniform magnetic field of 1.5 T is produced by a large magnet.

Question:

In a velocity selector, the uniform magnetic field of 1.5 T is produced by a large magnet. Two parallel plates with a separation of 1.5 cm produce the perpendicular electric field. What voltage should be applied across the plates so that
(a) A singly charged ion traveling at 8.0 x 104 m/s will pass through undeflected and
(b) A doubly charged ion traveling at the same speed will pass through undeflected?