什么是 Lorentz force？

A particle of charge $q$ moving at velocity $\vect v$ in an electric field $\vect E$ and a magnetic field $\vect B$ receives the force

The electric part is along $\vect E$ (or opposite, for $q < 0$) and independent of the motion; the magnetic part is perpendicular both to $\vect v$ and to $\vect B$, proportional to the speed, and vanishes for a particle at rest. Units: $\vect E$ in $\mathrm{V}/\mathrm{m}$ (or $\mathrm{N}/\mathrm{C}$), $\vect B$ in teslas ($\mathrm{T}$): $1\,\mathrm{T} = 1\,\mathrm{N}/(\mathrm{A}\,\mathrm{m})$.