The Operation of Electric Motors


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I have written this science research paper to help people understand more about the electric motors and their operation. The electric motor transforms electrical energy into mechanical energy, which in turn makes motion possible. To better understand electric motors, one should first understand the basics of electric motors operation, electromagnetics.

One 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 magnet creates 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 repel? and the same holds true with an electromagnet. A simple electromagnet can be created by the use of a power source and a piece of wire as shown in Figure 1. The magnetic field created will be stronger then the magnetic field of the earth, effecting the compass and will cause the needle to move in the direction of this newly created magnetic field.



As current flows through the wire, a magnetic field is created around the wire. Figure 2 shows the circular shape of the magnetic field around the wire as if you were able to look down the end of 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 will always be perpendicular to the wire and the fields direction depends on the which 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. Figure 3 shows an example of a simple electromagnet by coiling a wire around a nail and connecting it to a power source. The magnetic field is amplified by each loop of wire around the nail.



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?. This allows an electric motor to rotate.

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In order to continuously change the direction of the electromagnetic field in a motor, we will need to continuously change the direction of the electric current to the electromagnet. This can easily be done just by constructing the motor in a certain way. Now we will look at the parts of a very simple DC electric motor. 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. These parts are shown in Figure 4.

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 allows 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.


Figure 5a shows the coil of the motor being energized that creates a magnetic field in the direction as shown by the black arrow along the armature. The armature will rotate in the clockwise direction because it is being pulled and pushed by the field magnet (opposites attract & likes repel) figure 5b. Figure 5c is at the point where 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 as shown in the direction by the black arrow along the armature. The armature will continue to rotate in the clockwise direction because it is being pulled and pushed by the field magnet (opposites attract & likes repel) figure 5d. 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 if 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 you 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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