E×B drift · crossed fields simulation

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?

▶ Run the simulationSee the measured result

Units: m/s — E×B drift speed v_d = |E×B|/B² = E/B at E = 10 kV/m, B = 10 mT: Thomson's velocity-selector speed

How the lab tests it

Cross 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.

What it checks

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