The electromagnet in a motor must rotate consistently in just one direction to transform electrical energy into mechanical energy. What causes this
rotation?
A. The terminals of the battery frequently switch from positive to
negative.
B. The commutator frequently reverses the direction of the current in
the loop of wire.
C. The poles of the permanent magnets keep switching between
north and south.
D. The commutator causes the loop of wire to keep turning in one
direction