The DC motor is made in two parts; the "rotating armature" and the "fixed field windings". The field windings, also called the "stator", surrounds the armature. The field windings are made of tightly wound coils of wire inside the motor case. The armature, also called the "rotor", is another set of coils of wire wound round the central shaft. The armature is connected to the field windings through "brushes". The brushes are spring loaded contacts pressing against the "commutator". The commutator sends the electricity in a circular pattern to armature windings. A "series-wound" motor has the armature and the field windings connected in series. A series-wound DC motor has a low electrical resistance. When voltage is applied to the motor, it makes a strong magnetic field inside the motor. This produces a high amount of torque, so it is good for starting a train. If more current than needed is sent to the motor, there would be too much torque and the wheels would spin. If too much current is sent to the motor, it could damage the motor. Resistors are used to limit the current when the motor starts.