D.C. Generators MCQs

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1.What fundamental principle does a direct current (D.C.) generator operate on?

Lenz's principleOhm's principleFaraday's electromagnetic induction lawNone of these

2.Under what condition can a series generator initiate self-excitation?

Only when there is no load currentOnly when the load current is presentRegardless of the load current magnitudeNone of the stated conditionsNot applicable

3.If the open circuit voltage of a compound generator is 250 V, what can be said about its terminal voltage when operating at full load?

It will drop below 250 VIt remains constant at 250 VIt can either exceed or fall below 250 VNone of the above

4.A series generator has a terminal voltage of 150 V at a load current of 5 A. What will the terminal voltage be if the load current rises to 10 A?

5.Under what condition can a shunt generator initiate self-excitation?

Only when the field circuit resistance is below the critical thresholdOnly when the field circuit resistance exceeds the critical thresholdRegardless of the resistance value in the field circuitNone of the above

6.For a DC generator, which value of voltage regulation is considered ideal?

7.Two DC shunt generators, each having an armature resistance of 0.02 ohms and a field resistance of 50 ohms, operate in parallel to deliver a combined load current of 1000 A. If their electromotive forces (e.m.f.) are 270 V and 265 V respectively, what will be the voltage at the bus bars?

8.What is the key requirement for two DC generators to operate in parallel successfully?

Identical kilowatt capacityMatching rotational speeds during operationSimilar drooping voltage characteristic curvesEqual percentage voltage regulationNone of the above

9.Why is an equalizer bar employed when two DC generators operate in parallel?

To enhance the series magnetic fluxTo boost the generated electromotive forceTo minimize the combined impact of armature reaction from both generatorsTo ensure that the two similar machines share the load current almost equallyTo synchronize the rotational speeds of the generators

10.When two generators operate simultaneously, under what circumstance can one generator start functioning as a motor?

The generator’s rotation direction is changedThe generator’s speed is raisedThe generator’s magnetic field is reducedThe generator supplies a disproportionately large portion of the loadThe generator is disconnected from the system

11.Which type of generator is most suitable for operation in parallel with others?

Shunt generatorsSeries generatorsCompound wound generatorsNo generators are suitable

12.Which type of generator provides a steady voltage output regardless of load variations?

Generator with self-excitationGenerator with separate excitationLevel-compounded generatorEvery one of the above

13.When a self-excited DC generator does not build up voltage during its initial test run, what should be the first corrective action?

Reverse the connections of the field windingRaise the resistance in the field circuitIncrease the prime mover's rotational speedInspect the armature's insulation resistanceTighten all electrical terminal connections

14.What is the primary cause of unstable parallel operation between flat and over-compounded generators?

Their voltage characteristics increase with loadDifferent turn counts in their series field coilsVariations in speed control of their prime moversDisparities in resistance of the series field windings

15.What is the purpose of using an equalizer bar when two DC series generators operate in parallel?

To boost the rotational speed and consequently the generated voltage.To enhance the magnetic flux in the series winding.To ensure that both identical machines share the load current nearly equally.To minimize the combined impact of armature reaction from both generators.

16.Why are shunt generators considered ideal for maintaining stable parallel operation?

Because they exhibit increasing voltage behaviorDue to their uniform voltage responseOwing to their voltage characteristics that decrease with loadAs a result of their consistent linear voltage output