1. The problem statement, all variables and given/known data A singly charged positive ion has a mass of 2.50 x 10^-26kg. After being accelerated through a potential difference of 250 V, the ion enters a magnetic field of 0.500 T, in a direction perpendicular to the field. 2. Relevant equations Calculate the radius of the path of the ion in the field. 3. The attempt at a solution Firstly, I drew this picture to try to help me with the problem: http://img411.imageshack.us/img411/4197/picxc7.jpg [Broken] I've tried to set Fm = Fe, therefore coming up with the derived equation of V=E/B, but I don't know E. I then tried to find the electric field by using the voltage, but I don't know the distance. (V=ED) I also tried setting Fm = Fc, getting Bqv = mv^2/r, and finally resulting in Bqr/v=m. I had B, q, and m, but I didn't have r and v. Thanks for reading.