DC Motor

   An electric motor is a machine which converts electrical energy into mechanical energy.

Principle:
    It is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming's Left-hand rule and whose magnitude is given by
                     Force, F = B I l newton     
                       Where B is the magnetic field in weber/m².
                                 I is the current in amperes and 
                                 l is the length of the coil in meter.             
The force, current and the magnetic field are all in different directions. 
    If an Electric current flows through two copper wires that are between the poles of a magnet, an upward force will move one wire up and a downward force will move the other wire down.     

Figure 1: Force in DC Motor	Figure 2 : Magnetic Field in DC Motor
Figure 3 :  Torque in DC Motor	Figure 4 : Current Flow in DC Motor

    The loop can be made to spin by fixing a half circle of copper which is known as commutator, to each end of the loop. Current is passed into and out of the loop by brushes that press onto the strips. The brushes do not go round so the wire do not get twisted.  This arrangement also makes sure that the current always passes down on the right and back on the left so that the rotation continues. This is how a simple Electric motor is made.