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Electrical Engineering Objective Questions { DC Motors }

274.  A 230 V D.C. shunt motor takes 32 A at full load. The back e.m.f. on full load, if the resistance of motor armature and shunt field winding are 0.2 and 115 fl respectively, will be
A.210 V
B.215 V
C. 220 V
D. 224 V
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275.  Which of the following methods is most economical for finding the no-load losses of a large D.C. shunt motor?
A. Retardation test
B. Swinburne's test
C. Hopkinson's test
D. none of the above
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276.  In a D.C. motor constant torque is produced due to
A. Rotor laminations
B. end-plates
C. pole shoes
D. commutator
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277.  A D.C. series motor, as compared to shunt and compound motors, has the highest torque at the start because of its comparatively
A. stronger series field
B. lower armature resistance
C. large armature current
D. fewer series turns
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278.  Which of the following motors, on removal of load, will run at the highest speed?
A. Shunt motor
B. Series motor
C. Differential compound
D. Cumulative compound
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279.  The mechanical power developed by a D.C. motor is equal to
A. power input + losses
B. back e.m. f. x armature current
C. power output x losses
D. power output x efficiency
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280.  The variable resistor shunting the field of a D.C. series motor is called a
A. armature divertor
B. voltage regulator
C. field divereor
D. potential divider
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