English: Diagram showing the forces on an
electron in a metal sheet moving to the right under a magnet
, explaining
eddy currents, and where the drag force on the sheet comes from. The red dot
shows an electron in the metal under the magnet right after it has undergone a collision, and
shows the same electron after it has been accelerated by the magnetic field. On average at
the electron has the same velocity as the sheet
(black arrow). in the
direction. The magnetic field (
,
green arrow) of the magnet's North pole N is directed down in the
direction. The magnetic field exerts a
Lorentz force on the electron
(pink arrow) of
, where
e is the electron's charge. Since the electron has a negative charge, from the
right hand rule this is directed in the
direction. At
this force gives the electron a component of velocity in the sideways direction (
.
black arrow) The magnetic field acting on this sideways velocity, then exerts a Lorentz force on the particle of
. From the right hand rule, this is directed in the
, opposite to the velocity
of the metal sheet. This force accelerates the electron giving it a component of velocity opposite to the sheet. Collisions of these electrons with the atoms of the sheet exert a drag force on the sheet.