ITI Electrecian Theory Paper Semester III 2017 with Answer Key.

Choose the correct answer.
1.The frame of induction motor generator made of :
A)Silicon steel
B)Cast iron
C)Aluminum
D)Mild steel
Answer- B) Cast Iron.

2.In squirrel cage induction Motor the rotor slots are slightly skewed in order to:
A) Reduce windage losses.
B) Reduce eddy currents
C) Reduce accumulation of dirt and dust.
D) Reduce magnetic hum.
Answer- D) Reduce magnetic hum

3) Slip rings are usually made up of..
A) carbon
B) Phosphor bronze
C) Copper
D) Aluminum
Answer- B) Phosphor bronze

4) A capacitor start single phase motor will usually have a power factor of..
A) unity
B) 0.8 lagging
C) 0.6 lagging
D) 0.6 leading
Answer- C) 0.6 lagging

5.Which of the following method is most economical method of starting a single phase motor?
A) Resistance start method
B) capacitor start method
C) spilt phase method
D) inductance start method
Answer- B) Capacitor start method

6. In split phase motor the ratio of number of turns for starting winding to that of running winding is-
A) 2.0
B) >1
C) 1.0
D) <1
Answer- D) <1 (less than one)

7. A single phase motor generally used for small air compressor is..
A) capacitor start capacitor run
B) split phase
C) Reluctance type
D) Shaded pole
Answer- A) capacitor start capacitor run

8. A universal motor is on which..
A) can run on large variations in A.C. supply voltage
B) has infinitely varying speed
C) can operate on D.C as well as A.C
D) can work on 1Φ or 3Φ supply
Answer- C) can operate on D.C as well as A.C.

9. The motor used in compressor of house hold refrigerators is..
A) D.C. series motor
B) shaded pole motor
C) Universal motor
D) 1Φ induction motor
Answer- D) 1Φ induction motor

10. Single phase motors are commercially manufactured upto..
A) 1H.P.
B) 2 H.P.
C) 5H.P.
D) 10H.P.
Answer- B) 2H.P

11. The direction of universal motor can be reserved by..
A) Reversing the supply terminals
B) Switching from single phase to D.C.
C) Inter changing the brush leads
D) None of these
Answer- C) Inter changing the brush leads

12. What are the advantages of parallel operation of alternator?
A) Increase in reliability
B) Increase in efficiency under light
C) continuity in supply is maintained
D) All of these
Answer- D) All of these

13. When excitation is increases (over-excited) the synchronous generator operates at..
A) Unity power factor
B) Lagging power factor
C) Leading power factor
D) None of these
Answer- C) Leading power factor

14) In a synchronous generator, if the mechanical input is increased, with constant excitation, the load angle will be..
A) Increase
B) Decrease
C) Either increase or decrease
D) None of theseJ
Answer- A) Increase

15.In synchronous generator V curve is drawn between
A) field current on X-axis and armature current on Y-axis
B) field current on Y-axis and armature current on X-axis
C) either of these
D) field current on X-axis and power factor on Y-axis
Answer-A) field current on X-axis and armature current on Y-axis

16) Practically in most of the alternators which type of construction is preferred..
A) Rotating field type
B)  Rotating armature type
C)  Both are equally important
D) None of these
Answer- A) Rotating field type

17. Salient pole type rotors are generally used in hydro generation power plants. The limiting factor for size of rotor is..
A) Rotating field construction

B) Rotating Armature construction

C) Centrifugal force acting on the rotating member
D) All of these
Answer- C) Centrifugal force acting on the rotating member

18. In a synchronous machine if Φ is the flux per pole and f is the frequency of induced e.m.f. then..
A) E∝Φf
B) E∝ Φ/f
C) E∝ 1/Φf
D) E∝ f/Φ
Answer- A) E∝Φf

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