I have the following exercise: I have a charge (q) accelerated by a potential difference ($ \Delta V$) which enters a region in which a magnetic uniform field is present (the field is not know). I have the distance FO and I have to determinate the distance OS, where 'S' is the point of impact on the "Schermo". The magnetic field B and the particle speed v forms an angle of 90°
That's my idea: The electrostatic field is conservative so I can write this: $$ \Delta K = W_T = - \Delta U_e = q\Delta V $$ so: $ 1/2 m v^2 = q\Delta V => v^2 = 2q\Delta V / m $
Now when the charge reaches the "magnetic region" moves in circular motion because of the Lorentz Force with this radius: $ qvB = mv^2 / R => R = mv/qB $
I can't go on with the exercise because I haven't got the magnetic field B. Can you please help me completing this? Thank you so much :(