The Lorentz force  

This animation is a cartoon showing the cross-product Lorentz force induced by a charged particle travelling through a magnetic field B with a velocity v. The electron motion is indicated by the blue arrow pointing left, conventional current by the blue arrow to the right; the magnetic field is indicated by the golden arrow, which cycles through one full circle in the vertical plan containing the electron current. The resulting Lorentz force is shown by the red arrow. 

Note that in addition to the main matlab code, there is the function mArrow3.m used to generate fancy 3D arrows, which I downloaded from MathWorks File Exchange, and for which I credit Georg Stillfried. I use this function in several of the matlab codes available here. 

Matlab code