Motional emf
(E9.2.1) E9.2 · Motional EMF →The emf across a rod of length L moving at speed v perpendicular to a field B.
| induced emf | V | |
| field strength | T | |
| rod length | m | |
| rod speed | m/s |
A straight conductor moving at constant velocity perpendicular to a uniform field.
Assumes a straight conductor moving at constant velocity strictly perpendicular to a uniform field — a rotating or non-perpendicular geometry needs the flux-rule derivation instead.
The magnetic force on the rod's free charges, qv×B, pushes them along its length until the resulting electric field balances the magnetic force — the same result also follows from computing dΦ/dt for the circuit's expanding area, a useful consistency check.
Two different-looking derivations — force on moving charges, or changing flux — must agree, since they describe the same physical situation from two directions.