# The DC (direct current) motor:

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The DC (direct current) motor:
Motors The DC (direct current) motor: Motors are all about magnetism. They use the attractive and repellant forces of opposite magnetic poles to produce motion. There are two types of motors that we use today, DC (direct current) and AC (alternating current). In this diagram there is a DC motor similar to the ones we built in class and is mainly made up of six parts: a field magnet, an armature, an axle, a commutator, two brushes, and most importantly a DC power supply (e.g. a battery).

The DC (direct current) motor:
Motors The DC (direct current) motor: How does a DC motor work? First we must discuss its parts. Field Magnet - basically just a permanent magnet Armature - an electromagnet If you were to take a horseshoe magnet and place a simple electromagnet (i.e. a nail inside of a closed coil hooked up to a battery) between it’s poles so that the like poles of the permanent magnet and electromagnet are aligned , and make it possible for that nail to pivot, what do you think would happen? The nail will turn until it aligns its south pole with the field magnet’s north pole and its north pole with the field magnet’s south pole, but will go no further than that. We can only continue the rotational movement if we change the direction of the flow of electrons by reversing the battery connections. This “flips” the electric field of the electromagnet causing another repulsion and attraction between the poles of the two magnets, pushing the nail around again to complete the circle.

The DC (direct current) motor:
Motors The DC (direct current) motor: Now, how can we flip the magnetic field without disconnecting then reconnecting the battery between half turns? In this image is the armature, commutator, and axle. The armature takes the place of the nail in the previous example. It consists of two metal plates joined together by a coil wrapped around them. Between the two plates is the metal axle, just a metal rod that will be placed on supports to allow movement of the armature. The metal commutator (in this diagram it is the broken green cuff around the axle) is connected to the ends of the wire wrapping the armature. All of these pieces form an open circuit containing only the electromagnet. The brushes are the parts used to close that circuit.

Motors The DC (direct current) motor:
In the diagram on the right the brushes are indicated in red. Each brush is hooked up to opposite battery ends. As the brushes come into contact with the commutator they form a closed circuit and generate a magnetic field in the armature causing it to turn. After it makes a half turn, the commutator comes into contact with the brushes again, only in the opposite connection, which reverses the magnetic field. The result of this repeated process is rotational motion and thus the motor works!

Motors The DC (direct current) motor:
Another explanation…

DC Motor Right hand rule:
The Index finger points in the direction of the current; Middle finger points in the direction of the magnetic field (N to S); Thumb direction indicates the direction of force.

Motors The AC (alternating current) motor:
“An important change came in the later 1880s and 1890s, when electric power companies began considering the switch to alternating current. Alternating current was perfect for the distribution of electric power over long distances, and it worked well with the Edison electric lamp, but no practical AC motor existed until the works of Galileo Ferraris in Italy and Nikola Tesla in the United States. Tesla’s contributions are remembered today more than Ferraris’ in part because Tesla was subsequently hired by the Westinghouse corporation, which used his patents along with many others to become one of the major producers of electric equipment. With a suitable AC motor available, AC power took off. It is still in use today.”

Motors The AC (alternating current) motor:
An alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. City lights viewed in a motion blurred exposure. The AC ‘blinking’ wave causes the lines to be dotted rather than constant.

AC Motor

AC Generator

AC Induction Motor (more efficient)

Here are some fun websites to go to!
Motors Here are some fun websites to go to! To see animation and explanation of basic motors go to: To see animation and information on how transistors (require an AC current to increase or decrease voltage within circuits) work go to: