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Electrical Engineering Objective Questions { DC Motors }

211.  The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is
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212.  The armature voltage control of D.C. motor provides
A. constant torque drive
B. constant voltage drive
C. constant current drive
D. none of the above
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213.  The speed regulation of a D.C. motor is
A. lowest speed highest speed
B. highest speed ? lowest speed average speed
C.No load speed
D. Full load speed
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214.  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
A. a resistance is connected in series with armature
B. a resistance is connected parallel to the armature
C. armature is temporarily open circuited
D. a high value resistor is connected across thefield winding
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215. The speed of a D.C. shunt motor can be increased by
A. increasing the resistance in armature circuit
B. increasing the resistance in field circuit
C. reducing the resistance in the field circuit
D. reducing the resistance in the armature circuit
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216. If 1a be the armature current, then speed of a D.C. shunt motor is
A. independent of la
B. proportional to la
C. varies as (1a)2
D. varies asIa
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217. In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will
A. remain unchanged
B. reducedto one-fourth value
C. increase four folds
D. be doubled
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