1. The problem statement, all variables and given/known data In the simple mass spectrometer shown in the figure below, positive ions are generated in the ion source. They are released, traveling at very low speed, into the region between two accelerating plates between which there is a potential difference ΔV. In the shaded region there is a uniform magnetic field B ; outside this region there is negligible magnetic field. The semicircle traces the path of one singly charged positive ion of mass M, which travels through the accelerating plates into the magnetic field region, and hits the ion detector as shown. Determine the appropriate magnitude and direction of the magnetic field B , in terms of the known quantities shown in the figure below (in addition to M and q, where q is the charge on an ion). Magnitude B = ? direction = ? 2. Relevant equations Fmag = dp/dtmag = qvB dp/dtmag = p(v/R) = p(omega), p = ymv omega = q_mag * b / (ym) 3. The attempt at a solution deltaV (I don't know what to do with electrical potential) M (mass) q (charge) d/2 = R (radius) v << c, y = 1, p = mv (approximation) Fmag = dp/dtmag qvB = p(v/R) qvB = p(v/(d/2)) qB = p/(d/2)) B = p/(d/2))/q B = 2p/dq, p = mv (approx.) B = 2Mv/dq This is wrong, probably because I'm not given velocity. However, I don't know how to get magnetic field without velocity? I think the problem is I don't know what to do with electric potential.