Electrical Machines
When the supply terminal of a DC shunt motor are interchanged

 The motor will run much faster in the same direction.
 The motor will stop.
  The motor will run at its normal speed in the same direction as before.
 The direction of rotation will reverse.

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Electrical Machines
A bipolar dc machine with interpoles has a main-pole flux of ф per pole and an interpole flux of Фᵢ per pole. The yoke of the machine is devide into four quadrants by the main-pole axis and The commutation axis. The flux-distribution in the quadrants will be

 ½ ( ф - фᵢ ) in all the four quadrants
 ½ ( ф + фᵢ ) in two diametrically opposite quadrants and ½ ( ф - фᵢ ) in the remaining two Quadrants
 ½ ( ф + фᵢ ) in two adjacent quadrants and ½ ( ф - фᵢ ) in the remaining two quadrants
 ½ ( ф + фᵢ ) in all the four quadrants

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Electrical Machines
In dc machines, the field system has to be provided on stator unlike synchronous machines Where in it could be on any member, because

 it gives more uniform air-gap flux distribution
 dc machines are comparatively low rating machines.
 commutator action is not possible otherwise
 it reduces field structure iron losses

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