McqMate
Chapters
| 101. |
A D.C. generator works on the principle of |
| A. | Lenz's law |
| B. | Ohm's law |
| C. | Faraday's law of electromagnetic induction |
| D. | none of the above |
| Answer» C. Faraday's law of electromagnetic induction | |
| 102. |
A series generator can self-excite |
| A. | only if the load current is zero |
| B. | only if the load current is not zero |
| C. | irrespective of the value of load current |
| D. | none of the above |
| Answer» B. only if the load current is not zero | |
| 103. |
A shunt generator can self-excite |
| A. | only if the resistance of the field circuit is less than critical value |
| B. | only if the resistance of the field circuit is greater than critical value |
| C. | irrespective of the value of the resis-tance in the field circuit |
| D. | none |
| Answer» A. only if the resistance of the field circuit is less than critical value | |
| 104. |
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be |
| A. | 150 V |
| B. | less than 150 V |
| C. | greater than 150 V |
| D. | none of the above |
| Answer» C. greater than 150 V | |
| 105. |
The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage |
| A. | will be less than 250 V |
| B. | will always be 250 V |
| C. | may be greater or less than 250 V |
| D. | none of the above |
| Answer» C. may be greater or less than 250 V | |
| 106. |
Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be |
| A. | 270 V |
| B. | 267.5V |
| C. | 265 V |
| D. | 257.4V |
| Answer» B. 267.5V | |
| 107. |
The essential condition for parallel operation of two D.C. generators is that they have ' |
| A. | same kW rating |
| B. | the same operation r.p.m. |
| C. | the same drooping voltage charac-teristics |
| D. | same percentage regulation |
| Answer» C. the same drooping voltage charac-teristics | |
| 108. |
When two D.C. generators are running in parallel an equilizer bar is used |
| A. | to increase the series flux |
| B. | to increase the generated e.m.f. |
| C. | to reduce the combined effect of ar-mature reaction of both the machines |
| D. | so that the two identical machines will pass approximately equal currents to the load |
| Answer» D. so that the two identical machines will pass approximately equal currents to the load | |
| 109. |
With a D.C. generator which of the following regulation is preferred ? |
| A. | 100% regulation |
| B. | infinite regulation |
| C. | 50% regulation |
| D. | 1% regulation |
| Answer» D. 1% regulation | |
| 110. |
Which generator would you prefer for feeding long D.C. transmission lines ? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Over compound generator |
| D. | Flat compound generator |
| Answer» C. Over compound generator | |
| 111. |
In a D.C. generator the critical resistance can be increased by |
| A. | increasing its field resistance |
| B. | decreasing its field resistance |
| C. | increasing its speed |
| D. | decreasing its speed |
| Answer» C. increasing its speed | |
| 112. |
The number of armature parallel paths in a two-pole D.C. generator having duplexlap winding is |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» B. 4 | |
| 113. |
For both lap and wave windings, there are as many commutator bars as the numberof |
| A. | slots |
| B. | armature conductors |
| C. | winding elements |
| D. | poles |
| Answer» C. winding elements | |
| 114. |
The series field of a short-shunt D.C. generator is excited by |
| A. | external current |
| B. | armature current |
| C. | shunt current |
| D. | load current |
| Answer» D. load current | |
| 115. |
As a result of armature reaction, the reduction in the total mutual air gap flux in aD.C. generator is approximately |
| A. | 40 percent |
| B. | 25 percent |
| C. | 10 percent |
| D. | 5 percent |
| Answer» D. 5 percent | |
| 116. |
Shunt generators are most suited for stable parallel operation because of their |
| A. | rising voltage characteristics |
| B. | identical voltage characteristics |
| C. | drooping voltage characteristics |
| D. | linear voltage characteristics |
| Answer» C. drooping voltage characteristics | |
| 117. |
The main factor which leads to unstable parallel operation of flat and over compounded generators is |
| A. | their rising voltage characteristics |
| B. | unequal number of turns in their series field windings |
| C. | unequal speed regulation of their primemovers |
| D. | unequal series field resistances |
| Answer» A. their rising voltage characteristics | |
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