Elements of Electrical and Electronics Engineering Mid - I, September - 2014

1.The purpose of load in an electric circuit is to ______
  • Increase the circuit current
  • utilize the electrical energy
  • Decrease the circuit current
  • none of the above
Answer: B
2.The total conductance of the circuit shown in below is ______
  • 13 S
  • 1.6 S
  • 6 S
  • 2.5 S
Answer: B
3.Two Electric lamps of 40W each are connected in parallel across A.C mains. The power consumed by the combination is ______
  • 20W
  • 60W
  • 80W
  • 100W
Answer: C
4.The yoke of a DC machine is made up of ______
  • Silicon steel
  • soft Iron
  • Aluminum
  • cast steel
Answer: D
5.A capacitor opposes ______
  • Change in current
  • Change in voltage
  • Both change in current and voltage
  • none of the above
Answer: B
6.Carbon brushes are used in a DC machine because ______
  • Carbon lubricates and polishes the commutator
  • Contact resistance is decreased
  • Carbon is cheap
  • None of the above
Answer: A
7.The Iron core is used to provide ______ of Transformer.
  • Increase the weight
  • provide tight magnetic coupling
  • Reduce Core losses
  • none of the above
Answer: B
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.In a 3 phase induction motor, the rotor speed is ______ the synchronous speed
  • Greater than
  • smaller than
  • Equal to
  • none of the above
Answer: B
10.A 12 pole, 3- alternator is coupled to an engine running at 500 rpm. The alternator supplies a 3- induction motor which has full load speed of 1440 r.p.m. The number of poles of the motor is ______
  • 4
  • 6
  • 8
  • 12
Answer: A
11.Kirchoff’s current law at a junction deals with _______________
Answer: Conservation of charge
12.A passive element in a circuit is one which _______________
Answer: Receives energy
13.An Electric circuit contains _______________
Answer: Both active and passive elements
14.The coupling field between electrical and mechanical system of a DC machine is _______________
Answer: Magnetic field
15.The armature of DC machine is laminated in order to reduce _______________
Answer: Eddy current loss
16.A DC motor runs at 1725 rpm at full load and 1775 rpm at no load. The speed regulation is _______________
Answer: 2.9%
17.A transformer does not possess _______________ changing property.
Answer: Power
18.The flux in the core of a single phase transformer is _______________
Answer: Purely alternative one
19.The stator of a 3 phase induction motor produces _______________ magnetic field.
Answer: Rotating
20.The synchronous speed of a 3 phase induction motor produces having 20 poles and connected to a 50HZ source is _______________
Answer: 300 rpm