186. In a dc shunt motor for given field and armature currents

1. 1. speed will be higher if the magnetic circuit is saturated than if the magnetic circuit is unsaturated

   
   
   

   2. speed will be higher if the magnetic circuit is unsaturated than if the magnetic circuit is saturated

   
   
   

   3. state of saturation of the magnetic circuit will have no effect on the speed of the motor.

   
   
   

   4. with unsaturated magnetic circuit the motor can acquire a dangerously high speed.

   
   
   

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   NA

   Correct Option: A

   NA

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187. Two coupled dc series motors with constant torque load are changed over from series to parallel connection across a fixed volt age supply. As compared to the original speed the set speed

1. 1. becomes √2 times

   
   
   

   2. becomes double

   
   
   

   3. becomes half

   
   
   

   4. remains same

   
   
   

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   NA

   Correct Option: B

   NA

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188. A dc series motor has linear magnetization and negligible armature resistance, the motor speed is
     where, T = load torque

1. 1. directly proportional to √T

   
   
   

   2. inversely proportional to √T

   
   
   

   3. directly proportional to T

   
   
   

   4. inversely proportional to T

   
   
   

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   NA

   Correct Option: B

   NA

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189. Armature reaction AT in a dc machine

1. 1. are in the same direction as the main poles

   
   
   

   2. are in direct opposition to the main poles

   
   
   

   3. make an angle of 90° with the main pole axis.

   
   
   

   4. make an angle with the main pole axis which is load dependent.

   
   
   

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   NA

   Correct Option: C

   NA

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190. Open slots are used in dc machine armature because

1. 1. of the ease with which winding can be placed inside the slots

   
   
   

   2. it increases induced emf per coil

   
   
   

   3. it reduces armature voltage drop

   
   
   

   4. it reduces coil reactance emf and hence aids in commutation.

   
   
   

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   NA

   Correct Option: D

   NA

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