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George Yousif
Jared Grogan
ENG 3060
10 June 2009
Mechanism Description: The Electric Motor
Civilization as we know it would seize to exist without a simple yet very important
invention; that being the electric motor. This description paper is to help people understand more
about the electric motor and its operation. Throughout this description process it will start to
become evident on how and why the electric motor is so important to the culture we live in
today. The electric motor transforms electrical energy into mechanical energy, which in turn
makes motion possible (Electric Motor). To better understand electric motors, one should first
understand the basics of an electric motor’s operation. This operation involves understanding the
magnetic field and how magnets are used while also learning how the seven parts of the motor
incorporate the principle of electromagnetism.
You can create an electromagnet by running an electric current through a wire which in
turn will create a magnetic field. An electromagnet may only be a temporary magnet but it has
the same magnetic properties as a permanent magnet. Any type of magnet will create a magnetic
field and this magnetic field will contain two ends or polls, one North and one South. The
fundamental law of magnets states that Opposites attract and likes repels and the same holds true
with an electromagnet (Brain, Marshall). A simple electromagnet can be created by the use of a
power or voltage source and a piece of wire. The magnetic field created will be stronger than the
magnetic field of the earth; this can be seen by placing a compass near the newly created
magnetic field and noticing the direction change.
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As current flows through the wire, a magnetic field is created around the wire. The
magnetic field itself is invisible, but the magnetic field strength can be measured through the use
of special equipment. The magnetic field weakens the further you move away from the wire and
the fields direction depends on the direction the current if flowing. Since the magnetic field is
always circular and perpendicular to the wire, the magnetic field can be increased simply by
creating a coil of wire (Electric Motor and Generators).
An electric motor depends upon magnetism to function, to be more specific,
electromagnetism. By continuously changing the direction of the electromagnetic field in a
motor, we take advantage of the basic magnet principle that, “opposites attract and likes repel”
(Brain, Marshall). This allows an electric motor to rotate. In order to continuously change the
direction of the electromagnetic field in a motor, we will need to continuously change the
direction of the electrical current to the electromagnet. This can easily be done just by
constructing the motor in a certain way.
Now moving on to the parts of a very simple DC electric motor (see figure 1). The motor
is made up of seven main parts which include the armature or rotor, commutator, brushes, coil,
axle, field magnet and a DC power source (Brain, Marshall). An electric motor operates in the
following manner. Electric current is supplied from the power source and it travels through wire
to the brushes which are flexible pieces of metal that allow for rotary contact with the
commutators. The commutators are metal contacts that connect to the electromagnet coil which
is wrapped around the armature all riding on the motors axel.
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Figure 1: Computer generated image of an electric motor.
The armature will rotate in the clockwise direction because it is being pulled and pushed
by the field magnet (opposites attract & likes repel). This is when the direction of the electric
current is changing due to the switching of the commutators. Now the magnetic field is quickly
flipped in the opposite direction. The armature will continue to rotate in the clockwise direction
because it is being pulled and pushed by the field magnet. In order to change the speed of the
motor, the strength of the magnetic field will need to change. This can be accomplished by
changing the current or voltage being supplied by the power source to the coil. The motor will
continue to rotate as long as electricity is flowing.
The operational principle of an electric motor is simple to understand as it all revolves
around magnetism. They are an integral part of modern civilization and are often taken for
granted. They surround us in our homes, running our wash machine, cool our houses and let us
watch our favorite DVDs. They allow the average person to ride the elevator to the top floor,
pump water for you to drink and are used to start you gas powered car. In the near future you
will be driving around town in an electric powered vehicle that would reduce our dependencies
on fossil fuels, which would help keep from polluting the environment as we all need to be good
stewards of the earth.
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Works Citied
Brain, Marshall. "How Electromagnets Work." 01 April 2000. HowStuffWorks.com. 10 June
2009. <http://science.howstuffworks.com/electromagnet.htm>
“Electric Motor.” 10 June 2009. Wikipedia.org 10 June 2009
<http://en.wikipedia.org/wiki/Electric_motor>
“Electric Motor and Generators.” 18 February 2009. University of South Wales 10 June 2009.
<http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html#c1>
“Figure 1: Electric Motor.” 18 October 2008. Photo. Wikipedia.org. 08 June 2009.
<http://commons.wikimedia.org/wiki/File:Electric_motor_cycle_3.png>