An electric motor is an energy conversion device like internal combustion engines, but instead of using the energy in a liquid fuel they use energy supplied by electricity. An electric motor requires an interaction between the rotating parts and the stationary parts. Two common types of interaction are conduction and induction. The principles of a conduction motor will be used to explain the function of electricity motors.
Electricity flowing through a conductor induces an electrical magnetic field around the conductor. This electromagnetic field will have a plus (+) and a
FIGURE 28.1. Simplified electric motor.
minus (-) polarity. When the electromagnetic field comes in contact with the permanent magnetic field supplied by the magnets, a force is produced, because similar polarities repel each other and opposite poles attract each other. The strength of the force is influenced by the strength of the current, the strength of the magnetic field and the angle between the conductor and the magnetic field, Figure 28.1.
In Figure 28.1, the commutator supplies electricity to the loop of wire. The electromagnetic field reacts with the permanent magnetic field supplied by the permanent magnets. This causes the wire loop to rotate. A conductive electric motor has many individual loops wrapped around the rotor and each one of them rotates a few degrees when they are energized by the commutator. Because a continuous series of loops become energized the rotor continues to rotate as long as power is being supplied to the commutator.
Many different types of motor are used and they are categorized by their type of electricity and the type of interaction they have between the rotating part and the stationary part of the motor. The following section will discuss some of the advantages and disadvantages of electric motors.
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