Principles of Electrical Engineering Mid - II, April - 2012

1.The field winding of a d.c shunt machine usually carries ______ of the rated current of the machine
  • 2% to 5%
  • 15% to 20%
  • more than 20%
  • less than 0.5%
Answer: A
2.A shunt generator delivers 195 A at a terminal p.d of 250 V. The armature resistance and shunt field resistance are 0.02Ω and 50Ω respectively. What is the value of generated e.m.f?
  • 246 V
  • 270 V
  • 254 V
  • 282 V
Answer: C
3.In a long-shunt compound-wound generator, the shunt field is connected parallel with
  • armature
  • parallel combination of armature and series field
  • series field
  • series combination of armature and series field
Answer: D
4.The speed of a d.c. motor can be controlled by changing
  • its flux
  • armature circuit resistance
  • applied voltage
  • all of the above
Answer: D
5.By putting controller resistance in series with the armature of a d.c motor, we can obtain speeds
  • above the normal speed only
  • below the normal speed only
  • above as well as below the normal speed
  • none of the above
Answer: B
6.The only disadvantage of field control method for controlling the speed of a d.c shunt motor is that it
  • give speeds lower than the normal speed
  • is wasteful
  • needs a large rheostat
  • adversely affects commutation
Answer: D
7.A transformer transfers electrical energy from primary to secondary usually with a change in
  • frequency
  • power
  • voltage
  • time period
Answer: C
8.The open-circuit test on a transformer is always made on
  • low-voltage winding
  • high-voltage winding
  • either low or high voltage winding
  • none of the above
Answer: A
9.The main winding and starting winding of a single-phase induction motor are connected in ________ across the supply
  • series
  • parallel
  • series-parallel
  • none of the above
Answer: B
10.A two-phase a.c. servometer has
  • wound rotor
  • cage rotor
  • wound or cage rotor
  • a rotor similar to that in d.c motors
Answer: B
1.In a cumulatively compounded generator, the shunt and series fields _________ each other.
Answer: aid
11.In a cumulatively compounded generator, the shunt and series fields _________ each other.
Answer: aid
12.The e.m.f equation of a d.c generator in terms of flux, poles etc is given by ___________.
Answer: Eg = PфZN/60A
13.The motor terminal voltage equation is given by ___________
Answer: V = Eb+ IaRa
14.The most economical method of finding no-load losses of a large d.c. machine is __________ test.
Answer: Swinburne’s test
15.The open-circuit test on a transformer gives _____________.
Answer: iron losses
16.A transformer has full-load copper loss of 400 W. The copper loss at half-full load will be __________.
Answer: 100 W
17.A 50 Hz, 4-pole, single-phase induction motor will have a synchronous speed of ________.
Answer: 1500 r.p.m
18.The full-load efficiency of a shaded-pole motor is about ___________ %.
Answer: 30 to 35 %
19.The amount of torque required to move a stepper motor one full step is called _______________.
Answer: holding torque
20.The O.C.C of a d.c. generator is also called its ________________ characteristic.
Answer: magnetic (or) no-load saturation