11-13-2014 motors and magnetic fields

• The Hall Voltage is the potential created across a current-carrying metal-strip when the strip is placed in a magnetic field perpendicular to the current flow in the strip. (Actually, the magnetic field does not have to be totally perpendicular to the strip, the magnetic field only needs to have a component that is perpendicular.)
• When the majority of charge carriers are positive, they are deflected to the top of the strip so that the top of the strip attains a higher positive potential. If the majority of the charge carriers are negative then the top of the strip will become negative and the polarity of the Hall voltage will reverse. 

this is a saint louis style motor. it consists of a wire wrapped iron core on an axis spindle. the wire ends are connected to a split ring commutator. the split ring rotates between the fixed contacts as as shown.