Cross an electric field with a magnetic one and charges march sideways. Does that drift speed depend on the charge or the mass — do heavy and light, plus and minus, drift apart?
▶ Launch the interactive simulationCross a uniform E (pointing up) with B (out of the plane) and launch four charges from rest in separate lanes: three of the same +q with masses m = 1, 2, 3, plus one with q = −1. Each is pushed by the Boris algorithm (half electric kick · exact magnetic rotation · half kick), tracing a cycloid; the lab time-averages each particle's drift velocity ⟨v⟩ from its trajectory and plots it against q and m.
the E×B drift velocity v_d = (E×B)/B² — speed E/B, perpendicular to BOTH fields and containing NO charge and NO mass: heavy charges trace fat slow loops (radius r = mE/qB² ∝ m), light ones tiny fast loops, the negative charge loops the other way — yet all four guiding centres drift in the same direction at the same rate, the measured ⟨v⟩(q,m) a flat line at E/B