162. Electrical machines (A) DC machine (B) Synchronous machine (C) Transformer (D) Induction machine Codes (P) Cassette tape recorder (Q) Ceiling fan (R) Hand drills S) Digital control s stem. : (a)A?P, B?Q, C?S, D?R
A.(b)A?S, B?R, C?P, D?Q
B. A?Q, B?P, C?R, D?S
C. A?R, B?P, C?S, D?Q
D.

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163.  A shunt motor is funning at its rated speed on rated load. If the field circuit gets suddenly opened
A. torque developed by the motor will be almost zero and the motor will stop without causing any damage to the motor
B. the motor will draw very high armature current but it will continue to drive the load at a reduced speed.
C. the motor would tend to race to a high speed while driving the load
D. the motor would draw very high armature current and will stall with consequent damage to the armature

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164.  When starting a differentially connected compound motor, it is desirable to short-circuit the series field winding to
A. avoid very high starting time
B. avoid excessive starting speed
C.
D.(c) prevent the motor from starting in the reverse direction

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165.  In a loaded dc generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will
A. improve with fall of terminal voltage
B. deteriorate with fall of terminal voltage
C. improve with rise in terminal voltage
D. deteriorate with rise in terminal voltage

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166.  A dc shunt motor is required to drive a constant power load at rated speed while drawing rated armature current.Neglecting saturation and all machine losses, if both the terminal voltage and the field current of the machine are halved, then
A. the speed becomes 2 pu (per unit) but armature current remains at 1 pu
B. the speed remains at 1 pu but armature current becomes 2 pu
C. both speed and armature current becomes 2 pu
D. both speed and armature current remain at 1 pu

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167.  The series winding of a cumulatively compounded dc motor is short-circuited while driving a load at rated torque. This results in
A. reduction in both the armature current and the motor speed.
B.increase in the armature current and reduction in the motor speed
C. increase in both the armature current as well as the motor speed
D. reduction in the armature current and increase in the motor speed

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168.  Consider the following statements regarding an electrical machine having cylindrical stator and salient-pole rotor : I. Reluctance torque is produced when rotor winding is excited. 2. Reluctance torque is produced when stator winding is excited.3. When both stator and rotor windings are excited, electromagnetic torque is produced.4. When both stator and rotor windings are excited, electromagnetic as well as reluctance torques are produced. Which of these statements are correct?
A. 2 and 4
B. 1 and 4
C. 1 and 3
D. 2 and 3

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