For a charge thrown perpendicular to the field lines, the magnetic force acts like the centripetal force.
Remember that when the charge enters the magnetic field forming an angle of 0º or 180º, it does not suffer the action of the magnetic force, therefore it describes a uniform rectilinear motion. However, when the charge penetrates the magnetic field perpendicularly, that is, forming an angle of 90º in relation to the magnetic field lines, the particle is subjected to a centripetal force, therefore, the charge starts to describe a uniform circular motion inside the magnetic field. magnetic field.
F mag = Fc
F ma g = F c