Engineering 101

To explain how a motor functions

Figure 1

Figure 1 shows a motor with its basic components. Two armatures are attached to a fulcrum and are wrapped in in #22 wire. Above the armature are two copper commutator plates. One end of the wires that are wrapped around the armatures are soldered too the commutator plates. The other end of the wires that are wrapped around the armatures are also connected to each other in order for a current to flow from one armature to the other. Electricity is supplied to the commutator plates by means of two brushes that rub against the commutator plates. The electricity that is supplied to the commutator plates is also supplied to the armatures (through the wires that are soldered onto the commutator plates) making them electromagnets, one being a north pole (labeled A) and the other being a south pole (labeled B). Away from the motor are two field magnets (electromagnets) connected to another battery.
When the brushes and the field magnets are connected to their respective batteries, the opposite polarities of the armatures and the field magnets causes repulsion between the two, and forces the motor to spin. This is shown in figure 2

Figure 2
Figure 2 shows the movement of the motor counter-clockwise. As the motor moves the commutator plates rub against the brushes. The brushes have been supplying electricity to the same plate from figure 1 to figure 2

Figure 3

Figure 3 shows what happens when the motor moves into the positon where the brushes touch both commutator plates. At this moment the battery shorts causing the voltage to become zero. There is no magnetism in the armatures but the motor continues to move due to its own momentum.

Figure 4

Figure 4 shows the moment when the motor moves so that the brushes now touch the other commutator plate. At this moment the polarity of the armatures switches. Now armature A which originally was the north pole, now become the south pole and armature B which was originally the south pole, is now the north pole. This reversal of polarity now continues the repulsion between the armatures and the field magnets and keeps the motor spinning.