Singal phase induction motor mcq part -6

1. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on
(a) running winding
(b) rotor winding
(c) field winding
(d) compensating winding

Ans: a

2. Which of the following statements regarding repulsion-start induction motor is incorrect ?
(a) It requires more maintenance of commutator and other mechanical devices
(b) It makes quite a bit of noise on starting
(c) In fractional horse power motors, it has replaced the capacitor motors
(d) It is not easily reversed

Ans: c

3. A.C. series motor as compared to D.C. series motor has
(a) smaller brush width
(b) less number of field turns
(c) more number of armature turns
(d) less air gap
(e) all of the above

Ans: e

4. Locked rotor current of a shaded pole motor is
(a) equal to full load current
(b) less than full load current
(c) slightly more than full load current
(d) several times the full load current

Ans: c

5. Speed control of a universal motor is achieved by
(a) varying field flux with tapped field windings
(b) connecting rheostat in series
(c) applying variable voltage by means of silicon controlled rectifier
(d) applying variable voltage by means of variable auto-transformer
(e) all of the above methods

Ans: e

6. Hysteresis motor is particularly useful for high-quality record players and tape- recorders because
(a) it revolves synchronously
(b) it is not subject to any magnetic or mechanical vibrations
(c) it can be easily manufactured in extremely small sizes of upto 1 W output
(d) it develops hysteresis torque which is extremely steady both in amplitude and phase

Ans: d

7. Which of the following statements regarding hysteresis motor is in incorrect ?
(a) It is extremely sensitive to fluctuations in supply voltage
(b) Its high starting torque is due to its high rotor hysteresis loss
(c) It is extremely quiet in operation
(d) It accelerates from rest to full-speed almost instantaneously

Ans: a

8. Which of the following statements regarding single-phase induction motoris correct
?
(a) It requires only one winding
(b) It can rotate in one direction only
(c) It is self-starting
(d) It is not self-starting

Ans: d

9. The starting winding of a single-phase motor is placed in
(a) armature
(b) field
(c) rotor
(d) stator

Ans: d

10. The speed of a universal motor is usually reduced by using
(a) gearing
(b) belts
(c) brakes
(d) chains

Ans: a

Singal phase induction motor mcq part -5

1. Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
(a) magnetic relay
(b) thermal relay
(c) centrifugal switch
(d) none of the above

Ans: a

2. If a single phase induction motor runs slower than normal, the most likely defect is
(a) worn bearings
(b) short-circuit in the winding
(c) open-circuit in the winding
(d) none of the above

Ans: a

3. Which of the following motors is used in tape-recorders ?
(a) Hysteresis motor
(b) Reluctance motor
(c) Capacitor-run motor
(d) Universal motor

Ans: a

4. Which of the following statements regarding two value capacitor motor is incorrect ?
(a) It is a reversing motor
(b) It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
(c) It has low starting as well as rush¬ing currents
(d) It has high starting torque

Ans: b

5. Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because
(a) it is comparatively cheaper
(b) it has almost non-destructible capacitor
(c) it has low starting as well as running currents at relatively high power factor
(d) it is quiet in operation

Ans: c

6. If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
(a) motor will not come upto speed
(b) motor will not carry the load
(c) current drawn by the motor will be excessively high
(d) electrolytic capacitor will, in all probability, suffer break down

Ans: d

7. In a universal motor, the most common cause of brush sparking is
(a) open armature winding
(b) shorted armature winding
(c) shorted field winding"
(d) high commutator mica
(e) all of the above

Ans: e

8. If starting winding of a single-phase induction motor is left in the circuit, it will
(a) run faster
(b) spark at light loads
(c) draw excessive current and overheat
(d) run slower

Ans: c

9. Most of the fractional horsepower motors have either
(a) hard and annealed bearings
(b) ball or roller bearings
(c) soft and porous bearings
(d) plain or sleeve bearings

Ans: d

10. Which of the following statements regarding reluctance-start motor is incorrect ?
(a) It is similar to reluctance motor
(b) It is basically an induction motor and not a synchronous one
(c) So far as its basic working principle is concerned, it is similar to shaded pole motor
(d) the air-gap between rotor and salient poles is non- uniform

Ans: a

11. To reverse the direction of rotation of acapacitor start motor while it is running we should
(a) disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
(b) disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
(c) reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
(d) reverse the direction of connections of the auxiliary winding and im-mediately connect it to supply

Ans: a

12. In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will
(a) become unstable
(b) draw excessive armature current and may burn out
(c) fall out of synchronism and come to stand still
(d) run as induction motor

Ans: d

13. Which of the following motors has two separate windings on the motor ?
(a) Repulsion motor
(b) Repulsion induction motor
(c) Repulsion start induction run motor
(d) None of the above

Ans: b

14. A shaded pole motor does not possess
(a) centrifugal switch
(b) capacitor
(c) commutator
(d) all of the above

Ans: d

15. In a A.C. series motor armature coils are usually connected to commutator
(a) through resistance
(b) through reactances
(c) through capacitors
(d) solidly

Ans: a

16. Which of the following statements regarding a reluctance motor is incorrect ?
(a) It cannot be reversed, ordinarily
(b) It requires no D.C. field excitation for its operation
(c) It is nothing else but a single-phase, salient pole synchronous-induction motor
(d) Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path bet¬ween stator and rotor

Ans: a

17. A universal motor is one which
(a) can be operated either on D.C. or A.C. supply at approximately the same speed and output
(b) can be marketed internationally
(c) runs at dangerously high speed on no-load

Ans: a

18. A repulsion motor is equipped with
(a) slip rings
(b) commutator
(c) both (a) and (b)
(d) none of the above

Ans: b

19. The capacitors used in single-phase capacitor motors have no
(a) voltage rating
(b) dielectric medium
(c) polarity marking
(d) definite value

Ans: c

20. If a D.C. series motor is operated on A.C. supply, it will
(a) spark excessively
(b) have poor efficiency
(c) have poor power factor
(d) all of the above

Ans: d

DC MOTOR PART MCQ PART -6

1. Which of the following loss in a D.C. generator is dissipated in the form of heat?
(a) Mechanical loss
(b) Core loss
(c) Copper loss
(d) All of the above

Ans: d

2. Which of the following losses are significantly reduced by laminating the core of a
D.C. generator ?
(a) Hysteresis losses
(b) Eddy current losses
(c) Copper losses
(d) Windage losses

Ans: b

3. The total losses in a well designed D.C. generator of 10 kW will be nearly
(a) 100 W
(b) 500 W
(c) 1000 W
(d) 1500 W

Ans: b

4. The condition for maximum efficiency for a D.C. generator is
(a) eddy current losses = stray losses
(b) hysteresis losses = eddy current losses
(c) copper losses = 0
(d) variable losses = constant losses

Ans: d

5. D.C. generators are normally designed for maximum efficiency around
(a) full-load
(b) rated r.p.m.
(c) rated voltage
(d) all of the above

Ans: a

6. In a D.C. generator, the iron losses mainly take place in
(a) yoke
(b) commutator
(c) armature conductors
(d) armature rotor

Ans: d

7. D.C. generators are installed near the load centres to reduce
(a) iron losses
(b) line losses
(c) sparking
(d) corona losses

Ans: b

8. The purpose of retardation test on D.C. shunt machines is to find out
(a) stray losses
(b) eddy current losses
(c) field copper losses
(d) windage losses

Ans: a

9. Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
(a) Swinburne's test
(b) Hopkinson's test
(c) Field test
(d) Brake test

Ans: c

10. Hopkinson's test on D.C. machines is conducted at
(a) no-load
(b) part load
(c) full-load
(d) overload

Ans: c

11. During rheostat braking of D.C. series motors
(a) motor is run as a generator
(b) motor is reversed in direction
(c) motor is run at reduced speed

Ans: a

12. For which types of D.C. motor, dynamic braking is generally used ?
(a) Shunt motors
(b) Series motors
(c) Compound motors
(d) All of the above

Ans: d

13. Which method of braking is generally used in elevators ?
(a) Plugging
(b) Regenerative braking
(c) Rheostatic braking
(d) None of the above

Ans: a

14. In variable speed motor
(a) a stronger commutating field is needed at low speed than at high speed
(b) a weaker commutating field is needed at low speed than at high speed
(c) same commutating field is needed at low speed than at high speed
(d) none of the above is correct

Ans: b

15. When the armature of a D.C. motor rotates, e.m.f. induced is
(a) self-induced e.m.f.
(b) mutually induced e.m.f.
(c) back e.m.f.
(d) none of the above

Ans: c

16. Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control
(a) drum type controller is used
(b) three point starter is used
(c) four point starter is used
(d) all above can be used

Ans: a

17. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
(a) this will make armature to take heavy current, possibly burning it
(6) this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
(c) nothing will happen to motor
(d) motor will come to stop

Ans: a

18. D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the
(a) series motor
(b) shunt motor
(c) compound motor
(d) any of the above

Ans: a

19. D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this
(a) series motor
(b) shunt motor
(c) compound motor
(d) any of the above

Ans: c

20. Which D.C. motor has got maximum self relieving property ?
(a) Series motor
(6) Shunt motor
(c) Cumulatively compounded motor
(d) Differentially compounded motor

Ans: a

21. In the D.C. motor the iron losses occur in
(a) the field
(b) the armature
(c) the brushes
(d) the commutator

Ans: b

22. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by
(a) reducing the field current
(b) decreasing the armature current
(c) increasing the armature current
(d) increasing the excitation current
(e) none of the above methods

Ans: a

23. One D.C. motor drives another D.C. motor. The second D.C. motor when excited and
driven
(a) runs as a generator
(b) does not run as a generator
(c) also runs as a motor comes to stop after sometime

Ans: a

DC MOTOR MCQ PART -5

1. If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
(o) regenerative
(b) plugging
(c) dynamic braking
(d) none of the above
(e) any of the above

Ans: b

2. Which of the following motors one will choose to drive the rotary compressor ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Universal motor
(d) Synchronous motor

Ans: d

3. If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will
(a) increase
(b) decrease
(c) remain same
(d) become zero

Ans: a

4. Why are the D.C. motors preferred for traction applications ?
(a) Torque and speed are inversely proportional to armature current
(b) Torque is proportional to armature current
(c) Torque is proportional to square root of armature current
(d) The speed is inversely proportional to the torque and the torque is proportional to square of armature current

Ans: d

5. Which of the following motors is usually used in house-hold refrigerators ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Single phase induction motor (split phase start or induction run motor)
(d) Reluctance motor
(e) Synchronous motor

Ans: c

6. Which of the following motors is most suitable for signalling devices and many kinds of timers ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Induction motor
(d) Reluctance motor

Ans: d

7. Which motor should not be started on no-load ?
(a) Series motor
(b) Shunt motor
(c) Cumulatively compounded motor
(d) Differentially compounded motor.

Ans: a

8. Ward-Leonard control is basically a
(a) voltage control method
(b) field divertor method
(c) field control method
(d) armature resistance control method

Ans: a

9. For constant torque drive which speed control method is preferred ?
(a) Field control
(b) Armature voltage control
(c) Shunt armature control
(d) Mechanical loading system

Ans: b

10. In Ward-Leonard control the lower limit of speed is imposed by
(a) residual magnetism of the generator
(b) core losses of motor
(c) mechanical losses of motor and gen¬erator together
(d) all of the above

Ans: a

11. The main disadvantage of the Ward-Leonard control method is
(a) high initial cost
(b) high maintenance cost
(c) low efficiency at Hght loads
(d) all of the above

Ans: d

12. Regenerative method of braking is based on that
(a) back e.m.f. is less than the applied voltage
(b) back e.m.f. is equal to the applied voltage
(c) back e.m.f. of rotor is more than the applied voltage
(d) none of the above

Ans: b

13. The hysteresis loss in a D.C. machine least depends on
(a) Frequency of magnetic reversals
(b) Maximum value of flux density
(c) Volume and grade of iron
(d) Rate of flow of ventilating air

Ans: d

14. In a D.C. generator all of the following could be the effects of iron losses except
(a) Loss of efficiency
(b) Excessive heating of core
(c) Increase in terminal voltage
(d) Rise in temperature of ventilating air

Ans: c

15. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?
(a) hysteresis loss
(b) field copper loss
(c) armature copper loss
(d) eddy current loss

Ans: c

16. Which of the following loss in a D.C. generator varies significantly with the load current ?
(a) Field copper loss
(b) Windage loss
(c) Armature copper loss
(d) None of the above

Ans: c

17. Torque developed by a D.C. motor depends upon
(a) magnetic field
(b) active length of the conductor
(c) current flow through the conductors
(d) number of conductors
(e) radius of armature
(f) all above factors

Ans: f

18. D.C. shunt motors are used for driving
(a) trains
(b) cranes
(c) hoists
(d) machine tools

Ans: d

19. In a manual shunt motor starter
(a) over load relay is connected in series and no volt relay in parallel with the load
(6) over load relay is connected in paral¬lel and no volt relay in series with the load
(c) over load relay and no volt relay are both connected in series with the load
(d) over load relay and no volt relay are both connected in parallel with the load

Ans: a

20. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
(a) Providing laminations in armature core
(b) Providing laminations in stator
(c) Using non-magnetic material for frame
(d) Using material of low hysteresis co-efficient for armature core material

Ans: d

DC GENERATOR MCQ PART -6

1. A shell-type transformer has
(a) high eddy current losses
(b) reduced magnetic leakage
(c) negligibly hysteresis losses
(d) none of the above

Ans: b

2. A transformer can have regulation closer to zero
(a) on full-load
(b) on overload
(c) on leading power factor
(d) on zero power factor

Ans: c

3. A transformer transforms
(a) voltage
(b) current
(c) current and voltage
(d) power

Ans: d

4. Which of the following is not the standard voltage for power supply in India ?
(a) llkV
(b) 33kV
(c) 66 kV
(d) 122 kV

Ans: d

5. Reduction in core losses and increase in permeability are obtained with transformer employing
(a) core built-up of laminations of cold rolled grain oriented steel
(b) core built-up of laminations of hot rolled sheet
(c) either of the above
(d) none of the above

Ans: a

6. In a power or distribution transformer about 10 per cent end turns are heavily insulated
(a) to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
(b) to absorb the line surge voltage and save the winding of transformer from damage
(c) to reflect the line surge and save the winding of a transformer from damage
(d) none of the above

Ans: a

7. For given applied voltage, with the increase in frequency of the applied voltage
(a) eddy current loss will decrease
(b) eddy current loss will increase
(c) eddy current loss will remain unchanged
(d) none of the above

Ans: c

8. Losses which occur in rotating electric machines and do not occur in trans formers are
(a) friction and windage losses
(b) magnetic losses
(c) hysteresis and eddy current losses
(d) copper losses

Ans: a

9. In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are
(a) hysteresis and eddy current losses
(b) friction and windage losses
(c) copper losses
(d) none of the above

Ans: a

10. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and
drawing a current of 10 A from 200 V A.C. supply is incorrect ?
(a) Its secondary current is 5 A
(b) Its secondary voltage is 400 V
(c) Its rating is 2 kVA
(d) Its secondary current is 20 A
(e) It is a step-up transformer

Ans: d

11 The secondary of a current transformer is always short-circuited under operating conditions because it
(a) avoids core saturation and high voltage induction
(b) is safe to human beings
(c) protects the primary circuit
(d) none of the above

Ans: a

12. In a transformer the resistance between its primary and secondary should be
(a) zero
(b) 10 Q
(c) 1000 Q
(d) infinity

Ans: d

13. A good voltage regulation of a transformer means
(a) output voltage fluctuation from no load to full load is least
(b) output voltage fluctuation with power factor is least
(c) difference between primary and secondary voltage is least
(d) difference between primary and secondary voltage is maximum

Ans: a

14. For a transformer, operating at constant load current, maximum efficiency will occur at
(a) 0.8 leading power factor
(b) 0.8 lagging power factor
(c) zero power factor
(d) unity power factor

Ans: d

15. Which of the following protection is normally not provided on small distribution transformers ?
(a) Overfluxing protection
(b) Buchholz relay
(c) Overcurrent protection
(d) All of the above

Ans: b

16. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
(a) Horn gaps
(b) Thermal overload relays
(c) Breather
(d) Conservator

Ans: a

17. The efficiency of two identical transformers under load conditions can be determined by
(a) short-circuit test
(b) back-to-back test
(c) open circuit test
(d) any of the above

Ans: b

18. Which of the following insulating materials can withstand the highest temperature safely ?
(a) Cellulose
(b) Asbestos
(c) Mica
(d) Glass fibre

Ans: c

19. Which of the following parts of a transformer is visible from outside ?
(a) Bushings
(b) Core
(c) Primary winding
(d) Secondary winding

Ans: a

20. The noise produced by a transformer is termed as
(a) zoom
(b) hum
(c) ringing
(d) buzz

Ans: b

21. Shunt generators are most suited for stable parallel operation because of their
(a) rising voltage characteristics
(b) identical voltage characteristics
(c) drooping voltage characteristics
(d) linear voltage characteristics

Ans: c

22. The main factor which leads to unstable parallel operation of flat and over compounded generators is
(a) their rising voltage characteristics
(b) unequal number of turns in their series field windings
(c) unequal speed regulation of their primemovers
(d) unequal series field resistances

Ans: a

23. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to
(a) reverse the field connections
(b) increase the field resistance
(c) increase the speed of primemover
(d) check armature insulation resistance

Ans: a

DC GENERATOR MCQ PART -5

1. Number of tappings for each equilizer ring is equal to
(a) number of pole pairs
(b) number of poles
(c) number of parallel paths
(d) number of commutator segments

Ans: a

2. A D.C. generator can be considered as
(a) rectifier
(b) primemover
(c) rotating amplifier
(d) power pump

Ans: c

3. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called
(a) rotor
(b) stator
(c) field
(d) armature

Ans: d

4. In a D.C. machine stray loss is the sum of
(a) total copper loss and mechanical loss
(b) armature copper loss and iron loss
(c) shunt field copper loss and mechanical loss
(d) iron loss and mechanical loss

Ans: d

5. Lap winding is composed of
(a) any even number of conductors
(b) any odd number of conductors
(c) that even number which is exact multiple of poles + 2
(d) that even number which is exact multiple of poles

Ans: a

6. In a D.C. generator in case the resistance of the field winding is increased, then output voltage will
(a) increase
(b) decrease
(c) remain unaffected
(d) fluctuate heavily

Ans: b

7. An exciter for a turbo generator is a
(a) separately excited generator
(b) shunt generator
(c) series generator
(d) compound generator

Ans: b
 

8. In case of a flat compounded generator
(a) voltage generated is less than the rated voltage
(b) generated voltage is proportional to the load on the generator
(c) voltage remains constant irrespec¬tive of the load
(d) speed varies in proportion to the load on the generator

Ans: c

9. Which of the following generator will have negligible terminal voltage while running on no-load ?
(a) Series generator
(b) Shunt generator
(c) Compound generator
(d) Separately excited generator

Ans: a

10 Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?
(a) Series generator
(b) Shunt generator
(c) Compound generator
(d) None of the above

Ans: d

11. In over compounded generator, full load terminal voltage is
(a) almost zero
(b) less than noload terminal voltage
(c) more than noload terminal voltage
(d) equal to no-load terminal voltage

Ans: c

12. In a level compounded D.C. generator, full load terminal voltage is
(a) negligibly low
(b) equal to no-load terminal voltage
(c) more than no-load terminal voltage
(d) less than no-load terminal voltage

Ans: b

13. The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except
(a) armature reaction
(b) armature resistance drop
(c) field weakening due to armature reaction and armature
(d) commutation

Ans: d

14. In a D.C. generator
(a) external resistance = internal char-acteristic - armature reaction
(b) internal characteristic = magnetisation characteristic - ohmic drop
(c) external characteristic = magnetisation characteristic - ohmic drop - armature reaction
(d) magnetisation characteristic = external characteristic

Ans: c

15. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave
(a) will be zero
(b) will be of 5 Hz
(c) willbeof5xiVHz
(d) will be of v Hz 5

Ans: b

16. A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be
(a) zero
(b) about 2 V
(c) about 50 V
(d) 220 V

Ans: b

17. In a separately excited generator supplying rated load the armature reaction ,
(a) is always present
(b) is always absent
(c) may be sometimes present
(d) none of the above

Ans: a

18. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be
(a) zero
(b) small
(c) the same as rated voltage
(d) high

Ans: a

19. Armature reaction in a generator results in
(a) demagnetisation of leading pole tip and magnetisation of trailing pole tip
(b) demagnetisation of trailing pole tip and magnetisation of leading pole tip
(c) damagnetising the centre of all poles
(d) magnetising the centre of all poles

Ans: a

20. Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.
(a) Series field
(b) Compensating field
(c) Inter pole field
(d) Shunt field

Ans: d

Three phase induction motor mcq part -5

1. The torque developed by a 3-phase induction motor least depends on
(a) rotor current
(b) rotor power factor
(c) rotor e.m.f.
(d) shaft diameter

Ans: d

2. In an induction motor if air-gap is increased
(a) the power factor will be low
(b) windage losses will be more
(c) bearing friction will reduce
(d) copper loss will reduce In an induction motor

Ans: a

3. In induction motor, percentage slip depends on
(a) supply frequency
(b) supply voltage
(c) copper losses in motor
(d) none of the above

Ans: c

4. When R2 is the rotor resistance, X2 the rotor reactance at supply frequency
and s the slip, then the condition for maximum torque under running conditions will be
(a) sR2X2 = 1 (b) sR2 = X2
(c) R2 = sX2 id) R2 = s2X2

Ans: c

5. In case of a double cage induction motor, the inner cage has
(a) high inductance arid low resistance
(b) low inductance and high resistance
(c) low inductance and low resistance
(d) high inductance and high resis¬tance

Ans: a

6. The low power factor of induction motor is due to
(a) rotor leakage reactance
(b) stator reactance
(c) the reactive lagging magnetizing current necessary to generate the magnetic flux
(d) all of the above

Ans: d

7. Insertion of reactance in the rotor circuit
(a) reduces starting torque as well as maximum torque
(b) increases starting torque as well as maximum torque
(c) increases starting torque but maxi-mum torque remains unchanged
(d) increases starting torque but maxi-mum torque decreases

Ans: a

8. Insertion of resistance in the rotcir of an induction motor to develop a given torque
(a) decreases the rotor current
(b) increases the rotor current
(c) rotor current becomes zero
(d) rotor current rernains same

Ans: d

9. For driving high inertia loods best type of induction motor suggested is
(a) slip ring type
(b) squirrel cage type
(c) any of the above
(d) none of the above

Ans: a

10. Temperature of the stator winding of a three phase induction motor is obtained by
(a) resistance rise method
(b) thermometer method
(c) embedded temperature method
(d) all above methods

Ans: d

11. The purpose of using short-circuit gear is
(a) to short circuit the rotor at slip rings
(b) to short circuit the starting resis¬tances in the starter
(c) to short circuit the stator phase of motor to form star
(d) none of the above

Ans: a

12. In a squirrel cage motor the induced e.m.f. is
(a) dependent on the shaft loading
(b) dependent on the number of slots
(c) slip times the stand still e.m.f. induced in the rotor
(d) none of the above

Ans: c

13. Less maintenance troubles are experienced in case of
(a) slip ring induction motor
(6) squirrel cage induction motor
(c) both (a) and (b)
(d) none of the above

Ans: b

14. A squirrel cage induction motor is not selected when
(a) initial cost is the main consideration
(b) maintenance cost is to be kept low
(c) higher starting torque is the main consideration
(d) all above considerations are involved

Ans: c

15. Reduced voltage starter can be used with
(a) slip ring motor only but not with squirrel cage induction motor
(b) squirrel cage induction motor only but not with slip ring motor
(c) squirrel cage as well as slip ring induction motor
(d) none of the above

Ans: c

16. Slip ring motor is preferred over squirrel cage induction motor where
(a) high starting torque is required
(b) load torque is heavy
(c) heavy pull out torque is required
(d) all of the above

Ans: a

17. In a star-delta starter of an induction motor
(a) resistance is inserted in the stator
(b) reduced voltage is applied to the stator
(c) resistance is inserted in the rotor
(d) applied voltage per1 stator phase is 57.7% of the line voltage

Ans: d

18. The torque of an induction motor is
(a) directly proportional to slip
(b) inversely proportional to slip
(c) proportional to the square of the slip
(d) none of the above

Ans: a

19. The rotor of an induction motor runs at
(a) synchronous speed
(b) below synchronous speed
(c) above synchronous speed
(d) any of the above

Ans: b

20. The starting torque of a three phase induction motor can be increased by
(a) increasing slip
(b) increasing current
(c) both (a) and (b)
(d) none of the above

Ans: c

21. Insertion of resistance in the stator of an induction motor
(a) increases the load torque
(b) decreases the starting torque
(c) increases the starting torque
(d) none of the above

Ans: b

Transmission and distribution mcq part -5

1. Pin type insulators are generally not used for voltages beyond
(a) 1 kV
(b) 11 kV
(c) 22 kV
(d) 33 kV

Ans: d

2. Aluminium has a specific gravity of
(a) 1.5
(b) 2.7
(c) 4.2
(d) 7.8

Ans: b

3. For transmission of power over a distance of 200 km, the transmission voltage should
be
(a) 132 kV
(b) 66 kV
(c) 33 kV
(d) 11 kV

Ans: a

4. For aluminium, as compared to copper, all the following factors have higher values
except
(a) specific volume
(6) electrical conductivity
(c) co-efficient of linear expansion
(d) resistance per unit length for same cross-section

Ans: b

5. Which of the following equipment, for regulating the voltage in distribution feeder,
will be most economical ?
(a) Static condenser
(b) Synchronous condenser
(c) Tap changing transformer
(d) Booster transformer

Ans: d

6. In a tap changing transformer, the tappings are provided on
(a) primary winding
(b) secondary winding
(c) high voltage winding
(d) any of the above

Ans: b

7. Constant voltage transmission entails the following disadvantage
(a) large conductor area is required for same power transmission
(b) short-circuit current of the system is increased
(c) either of the above
(d) none of the above

Ans: b

8. On which of the following factors skin effect depends ?
(a) Frequency of the current
(b) Size of the conductor
(c) Resistivity of the conductor material
(d) All of the above

Ans: d

9. The effect of corona can be detected by
(a) presence of zone detected by odour
(b) hissing sound
(c) faint luminous glow of bluish colour
(d) all of the above

Ans: d

10. For transmission of power over a distance of 500 km, the transmission voltage should
be in the range
(a) 150 to 220 kV
(b) 100 to 120 kV
(c) 60 to 100 kV
(d) 20 to 50 kV

Ans: a

11. In the analysis of which of the following lines shunt capacitance is neglected ?
(a) Short transmission lines
(b) Medium transmission lines
(c) Long transmission lines
(d) Medium as well as long transmission lines

Ans: a

12. When the interconnector between two stations has large reactance
(a) the transfer of power will take place with voltage fluctuation and noise
(b) the transfer of power will take place with least loss
(c) the stations will fall out of step because of large angular displacement between the
stations
(d) none of the above

Ans: c

13. The frequency of voltage generated, in case of generators, can be increased by
(a) using reactors
(b) increasing the load
(c) adjusting the governor
(d) reducing the terminal voltage
(e) none of the above

Ans: c

14. When an alternator connected to the bus-bar is shut down the bus-bar voltage will
(a) fall
(b) rise
(c) remain unchanged
(d) none of the above

Ans: c

15. The angular displacement between two interconnected stations is mainly due to
(a) armature reactance of both alternators
(b) reactance of the interconnector
(c) synchronous reactance of both the alternators
(d) all of the above

Ans: a

16. Electro-mechanical voltage regulators are generally used in
(a) reactors
(b) generators
(c) transformers
(d) all of the above

Ans: b

17. Series capacitors on transmission lines are of little use when the load VAR
requirement is
(a) large
(b) small
(b) fluctuating
(d) any of the above

Ans: b

18. The voltage regulation in magnetic amplifier type voltage regulator is effected by
(a) electromagnetic induction
(b) varying the resistance
(c) varying the reactance
(d) variable transformer

Ans: c

19. When a conductor carries more current on the surface as compared to core, it is due
to
(a) permeability variation
(b) corona
(c) skin effect
(d) unsymmetrical fault
(e) none of the above

Ans: c

20. The following system is not generally used
(a) 1-phase 3 wire
(b) 1-phase 4 wire
(c) 3-phase 3 wire
(d) 3-phase 4 wire

Ans: a

21. The skin effect of a conductor will reduce as the
(a) resistivity of conductor material increases
(b) permeability of conductor material increases
(c) diameter increases
(d) frequency increases

Ans: a

22. When a live conductor of public electric supply breaks down and touches the earth
which of the following will happen ?
(a) Current will flow to earth
(b) Supply voltage will drop
(c) Supply voltage will increase
(d) No current will flow in the conductor
(e) None of the above

Ans: a