141.  Speed control by varying the armature_ circuit resistance offers
A. constant power drive
B. variable power drive
C. constant torque drive
D. variable torque drive

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142.  The volt-ampere equation for a long shunt compound motor is given by
A. Vt = Ea + la ra
B. V1= Ea + la (ra + rs)
C. VI = Ea ? la ra
D. Vt Ea + la ra IL + rs

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143.  A differential compounded d.c. motor drives a constant torque load. If series field winding gets short circuited, then
A. armature Ia current decreases and speed to rises
B. la decreases and tom falls
C. Ia increases and tom rises
D. Ia remains constant and tom falls.

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144. A cumulatively compounded d.c. motor drives a constant power load. If series Em f expression field winding gets short circuited, then
A. armature current la increases and speed to rises
B. Ia remains constant and tom rises
C. Ia increases and tom falls
D. Ia decreases and tom falls.

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145. For a p-pole machine, the relation between electrical (0e) and mechanical (0m) degrees is given by
A. 0= ? 0
B. Oe p . Om e p m
C. Oe = Om
D. Oe = ?2 Om

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146. If the field winding of an unloaded de shunt motor gets opened while running, it will
A. stop
B. run with reduced speed
C. run with increased speed
D. rach

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147. A de cumulatively compounded motor delivers rated load torque at rated speed. If the series field is short-circuited, then the armature current and speed will
A. both decrease
B. both increase
C. increase and decrease respectively
D. decrease and increase respectively

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