Particle orbits.
A magnetic force changes direction.
Does it change speed?
This browser could not start WebGL. Try a browser with hardware acceleration enabled. The analytical model and measurements below still work.
The sideways force turns the velocity; its component parallel to B carries the particle along a helix.
Magnetic force ·Work by B 0 J
Equations & model limits
F = q(v × B)
The force is perpendicular to velocity, so it does no work: kinetic energy stays constant.
v⊥ = v sin θ · v∥ = v cos θ
r = mv⊥ / (|q|B) · T = 2πm / (|q|B)
Model particle: mass 1.673 × 10⁻²⁷ kg (proton mass), charge ±1.602 × 10⁻¹⁹ C. Choosing −e reverses charge only; it does not turn the model particle into an electron.
Uniform, static B only; no electric field, collisions, gravity or radiation. Nonrelativistic motion is solved analytically. The luminous trail is a particle path; faint straight guides show B. Vector lengths are normalized for visibility. The scene auto-fits each launch; playback is greatly slowed.
For zero field or a parallel launch, there is no orbit; radius and orbital period are shown as “—”. Changing parameters represents a new experiment, not a changing field acting on the existing particle.