How do electric motor work?

How does Electric motor works?

             An electric motor is an mechanical device that converts electrical energy into mechanical energy.

             Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines.

         Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They may be powered by direct current, e.g., battery powered portable device or motor vehicle, or by alternating current from a central electrical distribution grid . The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of ships, pipeline compressors, andwater pumps with ratings in the millions of watts. Electric motors may be classified by the source of electric power, by their internal construction, by their application, or by the type of motion they give.

    The physical principle behind production of mechanical force by the interactions of an electric current and a magnetic field, Faraday's law of induction, was discovered by Michael Faraday in 1831. Electric motors of increasing efficiency were constructed from 1821 through the end of the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators andelectrical distribution networks. The first commercially successful motors were made around 1873.

                                          

             

                                               

                              

                 

Principle:

Fleming left hand rule

       Stretch the thumb, fore finger and middle finger of your left hand such that they are mutually perpendicular. If the forefinger points in the direction of magnetic field and the middle finger points in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

               An electric motor is a rotating device that converts electrical energy in to mechanical energy.

Do you know how an electric motor works based on this principle?

CONSTRUCTION OF A MOTOR:

                     An electric motor consists of a rectangular coil ABCD of insulated copper wire. The coil is placed between two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of magnetic

field. The ends of the coil are connected to the two halves of a split ring.The inner side of these halves insulated and attached to an axle. The external

conducting edges touches two conducting stationary brushes B1 and B2, respectively.

WORKING STAGE:

                            Current in the coil ABCD enters from the source through conducting brush and flows back to the battery through another brush. Notice that the current in arm AB of the coil flows from A to B. In arm CD it flows from C to D, that is, opposite to the direction of current through arm AB. On applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm AB pushes it

downwards while the force acting on arm CD pushes it upwards. Thus the coil and the axle, mounted free to turn about an axis, rotate anti-clockwise. At half rotation it makes contact with the both brush. Therefore the current in the coil gets reversed and flows along the path DCBA.

                   A device that reverses the direction of flow of current through a circuit is called commutator. In electric motors, the split ring acts as a commutator. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was previously  pushed down is now pushed up and the arm CD previously pushed up is now pushed down. Therefore the coil and the axle rotate half a turn more in the same direction. The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and to the axle.