Lorentz Force: motion of a charged particle in a uniform magnetic field
The magnetic field is perpendicular to the screen. Positive B means the field points out of the screen,
negative B means it points into the screen. The particle moves in the plane, while
the Lorentz force keeps turning the velocity vector.
particle
velocity vector
magnetic force
trajectory
Particle and field
Initial velocity
Display
Show velocity vector
Show force vector
Show trajectory trail
In this model the magnetic force is always perpendicular to the instantaneous velocity,
so it changes the direction of motion but not the speed.
That is why a pure magnetic field does no work on the particle.