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D.C. Motors - section-1
  1. Which of the following application requires high starting torque?

    2. A.

     Lathe machine
    B.

     Centrifugal pump
    C.

     Locomotive
    D.

     Air blower

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  2. If the field of a D.C. shunt motor gets opened while motor is running

    3. A.

     The speed of motor will be reduced %
    B.

     The armature current will reduce
    C.

     The motor will attain dangerously high speed 1
    D.

     The motor will continue to run at constant speed

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  3. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?

    4. A.

     Providing laminations in armature core
    B.

     Providing laminations in stator
    C.

     Using nonmagnetic material for frame
    D.

     Using material of low hysteresis coefficient for armature core material

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  4. Which of the following loss in a D.C. generator is dissipated in the form of heat?

    5. A.

     Mechanical loss
    B.

     Core loss
    C.

     Copper loss
    D.

     All of the above

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  5. The hysteresis loss in a D.C. machine least depends on

    6. A.

     Frequency of magnetic reversals
    B.

     Maximum value of flux density
    C.

     Volume and grade of iron
    D.

     Rate of flow of ventilating air

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  6. Hopkinson's test on D.C. machines is conducted at

    7. A.

     No load
    B.

     Part load
    C.

     Full load
    D.

     Overload

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  7. Regenerative method of braking is based on that

    8. A.

     Back e.m.f. is less than the applied voltage
    B.

     Back e.m.f. is equal to the applied voltage
    C.

     Back e.m.f. of rotor is more than the applied voltage
    D.

     None of the above

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  8. In the D.C. motor the iron losses occur in

    9. A.

     The field
    B.

     The armature
    C.

     The brushes
    D.

     The commutator

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  9. In which of the following applications D.C. series motor is invariably tried?

    10. A.

     Starter for a car
    B.

     Drive for a water pump
    C.

     Fan motor
    D.

     Motor operation in A.C. or D.C.

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  10. In D.C. machines fractional pitch winding is used

    11. A.

     To improve cooling
    B.

     To reduce copper losses
    C.

     To increase the generated e.m.f.
    D.

     To reduce the sparking

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