| 1. | The main disadvantage of Hopkinson's test for finding efficiency of the shunt D.C. motors is that it ? | |
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needs one motor and one generator
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requires two identical shunt machines
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requires full-load power
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ignores any change in iron loss
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Report Question| 2. | Which of the following methods gives the greatest braking torque ? | |
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Regenerative braking
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Plugging
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Rheostatic braking
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None of the above
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| 3. | Hopkinson's test on D.C. machines is conducted at ? | |
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no-load
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part load
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full-load
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overload
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| 4. | Which of the following losses are significantly reduced by laminating the core of a D.C. generator ? | |
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Hysteresis losses
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Eddy current losses
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Copper losses
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Windage losses
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| 5. | Which loss in a D.C. generator does not vary with load as well as flux density ? | |
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Copper loss
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Eddy current loss
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Hysteresis loss
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Windage loss
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| 6. | As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit ? | |
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a resistance is connected in series with armature
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a resistance is connected parallel to the armature
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armature is temporarily open circuited
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a high value resistor is connected across the field winding
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| 7. | Which of the following law/rule can' he used to determine. the direction of rotation of D.C. motor ? | |
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Lenz's law
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Faraday's law
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Coloumb's law
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Fleming's left-hand rule
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| 8. | When two D.C. series motors are connected in parallel, the resultant speed is ? | |
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more than the normal speed
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loss than the normal speed
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normal speed
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zero
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| 9. | The speed of a D.C. series, motor is ? | |
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proportional to the armature current
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proportional to the square of the armature current
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proportional to field current
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inversely proportional to the armature current
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| 10. | Which D.C. motor is generally preferred for cranes and hoists ? | |
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Series motor
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Shunt motor
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Cumulatively compounded motor
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Differentially compounded motor
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