Electric motors find applications in many home electrical appliances, medical and industrial equipment and vary in design, sizes and shapes from miniature to giant size to fit in position and to suit its intended use.
Electric motor is vital to the function of a suction machine, electric cooling fan, compressor, some nebulizer, baby and laboratory incubator, zoom mechanism in microscopes, motorized up and down movement, collimator of X-Ray machine, blower, centrifuge, blender, mixer lot to mention but few.
A motor may be DC or AC powered with variations in speed but DC motors are usually more powerful however, some are universal that is you can power them by DC or AC as the case may be. When you understand how a motor works, its not difficult to understand the working principles of the rest because this device works by the magnetic effect of electricity.
Simply put, motor effect is produced when opposing magnetic poles interact where one is stationary and the other can move freely. The stationary magnet (permanent or electromagnet) is refers to as stator; the free electromagnet is refers to as the rotor. I will not go into details of the operation here but you can watch this video to see how this man demonstrated the working principles of electric motor.
I enjoin you to watch this video to the end for insight on basic principles of motor from electromagnets. In this video check to see how they implement the brush and commutator but remember not all motor uses brush and commutator. You can vary the speed and torque of some motor to suit your purpose; for some motor, you can also change direction to rotate either clockwise or anti-clock wise.
To get the best out of a motor, its important to know how you can vary the speed and change its direction of movement as desired. Bigger electric motor include over current and overload protection as part of its control.
Check this out for ac motors in action: