1. The problem statement, all variables and given/known data A Mass-spectrometer consists of cylindrical capacitor with inner radius R1=4.5 cm and outer radius R2=5.1cm. Ions enter the mass-spectrometer through a narrow slit which is situated in between the capacitor plates as shown on the picture. Uniform magnetic field B=0.4 T is applied parallel to the capacitor’s axis, direction out of the plane. Find potential difference that should be applied between capacitance’s plates in order for the lithium ion Li+7 (such ions have charge +e, mass 7m, m=1.67*10-27 kg) to go around the middle section of the capacitor, i.e. on the circle of R= 4.8 cm. Energy of incoming ions is 1200 eV. By how much the potential should be changed in order for lithium ions Li+6 to go around the same trajectory? 2. Relevant equations Looking through my text I found this info R= mv/qB 1/2mv^2=eV (V is the accelerating potential) 3. The attempt at a solution I am pretty sure this is wrong, but I found v using the first equation and then subbed in each velocity to find the accelerating potential for Li+7 and Li+6. I subtracted the accelerating potential of Li+7 from Li+6's to get my final answer. I completely ignored the 1200 eV so I am kind of worried. My final answer was 2946.9V-2525.92V=421V. Thanks.