A direct current motor includes an armature coil having at least three phase coils, a commutator having multiple commutator segments connected to the armature coil, a pair of brushes in slidable contact with the commutator to supply power to the phase coils through the commutator, a rotation shaft, and a ring varistor coaxially fixed to the rotation shaft and having a ring-shaped varistor body and multiple electrodes that are circumferentially arranged on a surface of the varistor body. Each commutator segment is connected to a corresponding electrode of the ring varistor. The electrodes of the ring varistor are paired to form electrode pairs. Each electrode pair includes any two of the electrodes. A capacitance of one electrode pair is different from a capacitance of another electrode pair.