basic principle of potentiometer

1 ANSWERS

1. amomipais82
   

   Hi There,
   An electric motor is a device which converts electrical energy into mechanical energy. A common motor works on direct current. So, it is also called DC motor.
   Principle
   
   When a rectangular coil carrying current is placed in a magnetic field, a torque acts on the coil which rotates it continuously.
   When the coil rotates, the shaft attached to it also rotates and thus it is able to do mechanical work.
   Construction and Working
   Parts of a DC Motor
   
   
   Armature
   
   A D.C. motor consists of a rectangular coil made of insulated copper wire wound on a soft iron core. This coil wound on the soft iron core forms the armature. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet.
   Commutator
   
   A commutator is used to reverse the direction of flow of current. Commutator is a copper ring split into two parts C1 and C2. The split rings are insulated form each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings.
   Brushes
   
   Two small strips of carbon, known as brushes press slightly against the two split rings, and the split rings rotate between the brushes.
   The carbon brushes are connected to a D.C. source.
   
   Working of a DC Motor
   
   When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn towards the right, causing rotation.
   
   
   When the coil turns through 900, the brushes lose contact with the commutator and the current stops flowing through the coil.
   However the coil keeps turning because of its own momentum.
   
   Now when the coil turns through 1800, the sides get interchanged. As a result the commutator ring C1 is now in contact with brush B2 and commutator ring C2 is in contact with brush B1. Therefore, the current continues to flow in the same direction.
   The Efficiency of the DC Motor Increases by:
   
   
   
   Increasing the number of turns in the coil
   Increasing the strength of the current
   Increasing the area of cross-section of the coil
   Increasing the strength of the radial magnetic field

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