Class 10 Physics Magnetic Effects of Electric Current Electric Motor

Electric Motor

Electric motor is a device that converts electrical energy to mechanical energy.

Parts of a Electric Motor

  • Insulated Copper wire: A rectangular coil of wire ABCD
  • Magnet Poles: A magnet as placed above ie North Pole and South Pole. This creates a magnetic field as shown above.
  • Split Rings: Two disjoint C-shaped rings P and Q. It acts as a commutator (which can reverse the direction of current)
  • Axle: The split rings are placed on the axle which can rotate freely.
  • Brushes: The outside of the split rings are connected to conducting brushes X and Y.
  • Source Battery: To source current.

Working

  • When the current begins to flow, current flows through brush X, then A to B, B to C, C to D and then to brush Y and into the battery.
  • Now applying Fleming's Left Hand Rule to wire AB, Current is along AB, Magnetic Field is as shown (North-> South), the motion of the wire is downwards.
  • Now applying Fleming's Left Hand Rule to wire CD, Current is along CD, Magnetic Field is as shown (North-> South), the motion of the wire is upwards.
  • The rectangular coil begins to move in the anti-clockwise direction
  • Note that during anti-clockwise motion, the split rings and axle also move, whereas the brushes don't move.
  • After half a rotation, Wire CD and Split ring Q moves to the left.  Wire AB and Split ring P moves to right. Brushes X and Y donot move.
  • Now applying Fleming's Left Hand Rule to wire CD, Current is along DC. (Battery -> Split ring Q -> DC , Magnetic Field is as shown (North-> South), the motion of the wire is downwards.
  • Now applying Fleming's Left Hand Rule to wire AB, Current is along BA. (Battery -> Split ring Q -> DC --> CB -> BA --> Split ring P) , Magnetic Field is as shown (North-> South), the motion of the wire is upwards.
  • So, again the coil rotates in the anti-clockwise direction.
  • The reversal of current in the coil results in the continous rotation of the coil. The reversal of current is achieved by the commutator rings

Applications

  • Electric Fans
  • Refrigerators
  • Mixers
  • Washing machines

 

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