Multiple Choice Questions Topic Outline
- MCQs in Cells and Batteries
- MCQs in Electric Generator
- MCQs in Electronic Power Supply
- MCQs in Voltage Regulation
- MCQs in Photovoltaic/Thermoelectric Generator
- MCQs in Distribution Transformer
- MCQs in Uninterrupted Power Supply (UPS)
- MCQs in Float-Battery System
- MCQs in Converters
- MCQs in Inverters
The Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part 4 of the Series
151. The friction and wind age losses in a dc motor depends upon
- A. speed
- B. armature current
- C. flux
- D. field and armature resistance
152. If a transformer core has air gaps then
- A. reluctance of magnetic path is decreased
- B. hysteresis loss is decreased
- C. magnetizing current is greatly increased
- D. eddy current is increased
153. The effect of leakage flux in a transformer is to
- A. increase copper losses
- B. decrease copper losses
- C. cause voltage drop in the windings
- D. reduce eddy current losses
154. The iron losses in a dc motor depend upon
- A. flux only
- B. both flux and speed
- C. speed only
- D. temperature
155. The greatest percentage of power loss in a dc motor is due to
- A. wind age loss
- B. core loss
- C. copper loss
- D. friction loss
156. Excessive sparking at the brushes may caused due to
- A. dirt on the commutator
- B. misalignment of machine
- C. loose coupling
- D. worn bearings
157. The temperature rise of a transformer is directly proportional to
- A. apparent power
- B. leakage reactance
- C. reactive power
- D. true power
158. A graphical relation between the generated emf and the field current of a machine
- A. current generation curve
- B. voltage generation curve
- C. voltage current curve
- D. magnetization curve
159. Majority of alternators in use have
- A. revolving ac armature winding
- B. stationary field type construction
- C. revolving field type construction
- D. stationary ac armature winding
160. The stator of an alternator is identical to that of a
- A. dc generator
- B. 1 phase induction motor
- C. 3 phase induction motor
- D. Rosenberg generator
161. Excessive motor vibration is caused by
- A. too much brush tension
- B. open armature coil
- C. worn bearings
- D. bent shaft
162. Hot bearings of a dc motor may be caused by
- A. poor ventilation
- B. loose coupling
- C. incorrect voltage
- D. lack of dirty lubricant
163. Intermittent sparking at the brushes of dc motor may be caused due to
- A. an open armature coil
- B. loose coupling
- C. intermittent load
- D. incorrect voltage
164. When the load on a transformer is increased, the eddy current loss
- A. is decreased
- B. remains the same
- C. is increased
- D. becomes zero
165. The yoke of a dc machine is made of
- A. silicon steel
- B. aluminum
- C. soft iron
- D. cast steel
166. The armature of a dc machine is made of
- A. silicon steel
- B. cast steel
- C. wrought iron
- D. soft iron
167. The voltage per turn of the primary of a transformer is _____ the voltage per turn of the secondary
- A. more than
- B. the same as
- C. less than
- D. twice
168. The winding of the transformer with greater number of turns will be
- A. high voltage winding
- B. low voltage winding
- C. either high or low voltage winding
- D. high power
169. The coupling field between electrical and the mechanical systems of a dc machine is
- A. electric field
- B. both electric and magnetic fields
- C. magnetic field
- D. electromagnetic field
170. The real working Part of a dc machine is the
- A. commutator
- B. armature winding
- C. field winding
- D. stator
171. Which DC machines are the most common?
- A. 2 pole
- B. 6 pole
- C. 4 pole
- D. 8 pole
172. The core type transformer provides
- A. much longer magnetic pattern
- B. lesser average length per turn
- C. shorter magnetic path
- D. longer magnetic path
173. A machine with field excitation by both shunt and series windings
- A. complex machine
- B. compound machine
- C. universal machine
- D. shunt/ series machine
174. The armature winding of a dc machine is placed on the rotor to
- A. save iron
- B. facilitate commutation
- C. reduce losses
- D. reduce armature reaction
175. The yoke of a dc machine carries _____ poke flux
- A. one third of
- B. two times of
- C. one half of
- D. one fourth of
176. The greatest eddy current loss occurs in the ______ of a dc machine
- A. field poles
- B. commutating process
- C. yoke
- D. armature
177. The commutator pitch for a simplex lap winding is equal to
- A. number of poles of the machines
- B. 1
- C. poles pairs
- D. 2
178. In a simplex wave winding, the number of parallel paths is equal to
- A. number of poles in the machine
- B. 2
- C. number of pair poles
- D. 1
179. In a practical transformer, copper losses account for how many percent of the total losses?
- A. 75%
- B. 25%
- C. 85%
- D. 95%
180. By laminating the core of a transformer, ______ decreases
- A. leakage reactance
- B. eddy current loss
- C. hysteresis loss
- D. copper loss
181. The number of parallel paths in a simplex lap winding is equal to
- A. 2
- B. number of poles
- C. number of pair poles
- D. 1
182. In a dc machine the number of commutator segments is equal to
- A. number of conductors
- B. number of coils
- C. twice the number of poles
- D. twice the number of coils
183. A dc compound generator having full load terminal voltage equal to the no load generator voltage is called _______ generator
- A. under compounded
- B. flat compounded
- C. over compounded
- D. un compounded
184. The terminal voltage of a _____ generator vary widely with changes in load current
- A. series
- B. flat compounded
- C. shunt
- D. over compounded
185. The nature of armature winding of a dc machine is decided by
- A. front pitch
- B. back pitch
- C. commutator path
- D. number of coils
186. The voltage regulation of an alternator is larger than of a dc generator because of
- A. large armature resistance
- B. large leakage reactance
- C. complex effects of armature reaction
- D. small armature resistance
187. High voltage dc machines use what winding?
- A. Lap
- B. wave
- C. either lap or wave
- D. open circuit
188. In a lap winding, the number of the brushes required is equal to
- A. number of poles
- B. commutator pitch
- C. number of pairs of poles
- D. number of coils
189. What is the approximate efficiency of large transformer?
- A. 65%
- B. 80%
- C. 50%
- D. 95%
190. In a wave winding, the commutator pitch is approximately equal to
- A. pole pitch
- B. thrice the pole pitch
- C. twice the pole pitch
- D. half the pole pitch
191. A triplex wave winding will have _____ parallel paths
- A. 6
- B. 4
- C. 2
- D. 8
192. For a given dc generator, the generated voltage depends upon
- A. flux only
- B. both speed and flux
- C. speed only
- D. armature rotation
193. For the same rating, a dc machine has _____ an ac machine
- A. the same weight as
- B. less weight than
- C. more weight than
- D. half the weight than
194. Difference between the speed of a rotating magnetic field and the associated rotor
- A. split
- B. salient pole
- C. slip
- D. pull out torque
195. The field winding of a dc shunt machine usually carries _____ of the rated current of the machine
- A. 2% to 5%
- B. more than 20%
- C. 15% to 20%
- D. less than 0.5%
196. A separately excited dc generator is not used because
- A. it is costly
- B. a separate dc source is required for field circuit
- C. voltage drops considerably with load
- D. it is bulky
197. The effect of armature reaction is to
- A. decreased the total flux
- B. make the air gap flux uniform
- C. increase the total flux
- D. make the flux constant
198. In a dc generator armature reaction ______pole tip
- A. weakens the flux at the trailing
- B. weakens the flux at the leading
- C. strengthens the flux at the leading
- D. strengthens the flux at the trailing
199. The greatest percentage of the heat loss in a dc machine is due to
- A. eddy current loss
- B. copper loss
- C. hysteresis loss
- D. frictional loss
200. The size of a dc generator can be reduced by using
- A. lap winding
- B. high resistance winding material
- C. iron commutator
- D. magnetic material of high permeability
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