Electrical Systems Mid - II, November - 2014

1.When a two winding transformer is operated with lower copper loss, its efficiency is
  • same
  • decreased
  • increased
  • rises to 100%
Answer: C
2.The amount of leakage flux in the transformer windings depend upon
  • mutual flux
  • load current
  • applied voltage
  • turns ratio
Answer: B
3.The efficiency of a transformer at full load 0.85pf(lag) is 95%. Its efficiency at full load 0.85(lead) will be ____%
  • 95
  • 100
  • more than 95
  • less than 95
Answer: A
4.The load of a certain transformer is reduced to 50%, the copper loss would become
  • 0.25 times
  • 0.5 times
  • same
  • 2 times
Answer: C
5.Greater the secondary leakage flux less will be the
  • primary induced emf
  • secondary induced emf
  • secondary terminal voltage
  • primary terminal voltage
Answer: B
6.The efficiency of a given transformer is maximum when
  • it runs overload
  • it runs at full load
  • it runs at half full load
  • its Cu loss equals iron loss
Answer: D
7.Which motor will have the least %increase of output current for the same %increase in torque?
  • shunt
  • separately excited
  • series
  • cumulative compound
Answer: C
8.For maximum starting torque in an induction motor r2=________x2.
  • 1
  • 5
  • 0.5
  • 1.5
Answer: A
9.At a slip of 4% the maximum possible speed of three phase squirrel cage induction motor is ______ rpm.
  • 1440
  • 1500
  • 2880
  • 3000
Answer: C
10.In a single phase induction motor the main and auxiliary winding s are displaced by
  • 30
  • 0
  • 180
  • 90
Answer: D
11.The direction of rotation of the shaded pole motor is always from _________ towards the ___________ part of the pole.
Answer: unshaded and shaded
12.Starter is connected on rotor side in __________ induction motor.
Answer: slip ring
13.The minimum number of wattmeters required for measurement of active power in a three phase system is ________.
Answer: 2
14.Power developed by dc motor is maximum when the ratio of back emf and applied voltage is ______.
Answer: 0.5
15.The commutator segments of a dc machine are made of ___________.
Answer: copper
16.When pole flux remains constant, if the speed of the generator is doubled, the emf generated will become _____________.
Answer: twice
17._________ type of generator is used to charge batteries.
Answer: shunt
18.The characteristic drawn between no load generated emf and field current is known as ________________ characteristic.
Answer: internal
19.When the load of a dc shunt motor is increased, its speed ________________.
Answer: reduces
20.During SC test at full load current the power input to a transformer comprises predominantly ________ losses.
Answer: copper