# Multiple choice question for engineering

## Set 1

1. Voltage induce in the induction motor is highest at

a) starting

b) standstill

c) rated speed

d) any of the mentioned

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2. Starters are required in the induction motor because

a) of high starting current

b) they are not self starting

c) torque produced is very low at starting to overcome inertia

d) all of the mentioned

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3. Full voltage starting of induction motor may cause

a) dip in the voltages

b) high inrush current

c) high losses

d) all of the mentioned

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4. For a 4-pole, 50 Hz induction motor has starting current as 5 times to that of the full load current working at a speed of 1450rpm.

The ratio of starting to full load torque will be

a) 0.83

b) 0.17

c) 0.67

d) 1

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5. Starting methods applicable to both squirrel-cage and slip ring induction motors is/are

A. DOL starting

B. Auto transformer starting

C. Rotor resistance starting

a) A, B

b) A, B, C

c) B, C

d) A, C

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6. The method which employs reduction of the voltage while induction motor starting is/are

A. DOL starting

B. Auto transformer starting

a) Only A

b) A, B

c) Only B

d) Neither A nor B

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7. The method which employs raising of the voltage while induction motor starting is/are

A. DOL starting

B. Auto transformer starting

a) Only A

b) A, B

c) Only B

d) Neither A nor B

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8. External methods of induction motor starting is employed to

a) Reduce the voltage

b) Reduce the current

c) improve efficiency

d) all of the mentioned

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9. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of ‘x’, then the

starting current reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

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10. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of ‘x’, then the

starting torque reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

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11. Series reactor method of starting has main disadvantage of

a) lowering the starting power

b) increasing the starting current

c) increasing starting torque

d) all of the mentioned

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12. Series reactor method of starting has main disadvantage of lowering the starting power. This can be overcome by

a) using series resistance

b) using parallel reactor

c) using parallel resistance

d) using series reactor

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13. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of ‘x’, then the

starting current reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

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14. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of ‘x’, then the

starting torque will be

a) x *Tfl

b) x^2 *Tfl

c) 1/x *Tfl

d) no change in the starting current

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15. For the application requiring high starting torque and minimum starting current, the most suitable starting method will be

a) Auto transformer starting method

b) Reactance starting method

c) DOL method

d) Star-Delta method

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16. Auto transformer method of starting has most acceptable method for the starting of the induction motor due to

a) maximum torque

b) maximum reduction of inrush current

c) variable tapping

d) all of he mentioned

### View Answer

## Set 2

1. Voltage induce in the induction motor is highest at

a) starting

b) standstill

c) rated speed

d) any of the mentioned

### View Answer

2. Starters are required in the induction motor because

a) of high starting current

b) they are not self starting

c) torque produced is very low at starting to overcome inertia

d) all of the mentioned

### View Answer

3. Full voltage starting of induction motor may cause

a) dip in the voltages

b) high inrush current

c) high losses

d) all of the mentioned

### View Answer

4. For a 4-pole, 50 Hz induction motor has starting current as 5 times to that of the full load current working at a speed of 1450rpm.

The ratio of starting to full load torque will be

a) 0.83

b) 0.17

c) 0.67

d) 1

### View Answer

5. Starting methods applicable to both squirrel-cage and slip ring induction motors is/are

A. DOL starting

B. Auto transformer starting

C. Rotor resistance starting

a) A, B

b) A, B, C

c) B, C

d) A, C

### View Answer

6. The method which employs reduction of the voltage while induction motor starting is/are

A. DOL starting

B. Auto transformer starting

a) Only A

b) A, B

c) Only B

d) Neither A nor B

### View Answer

7. The method which employs raising of the voltage while induction motor starting is/are

A. DOL starting

B. Auto transformer starting

a) Only A

b) A, B

c) Only B

d) Neither A nor B

### View Answer

8. External methods of induction motor starting is employed to

a) Reduce the voltage

b) Reduce the current

c) improve efficiency

d) all of the mentioned

### View Answer

9. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of ‘x’, then the

starting current reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

### View Answer

10. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of ‘x’, then the

starting torque reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

### View Answer

11. Series reactor method of starting has main disadvantage of

a) lowering the starting power

b) increasing the starting current

c) increasing starting torque

d) all of the mentioned

### View Answer

12. Series reactor method of starting has main disadvantage of lowering the starting power. This can be overcome by

a) using series resistance

b) using parallel reactor

c) using parallel resistance

d) using series reactor

### View Answer

13. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of ‘x’, then the

starting current reduces by

a) x

b) x^2

c) 1/x

d) no change in the starting current

### View Answer

14. A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of ‘x’, then the

starting torque will be

a) x *Tfl

b) x^2 *Tfl

c) 1/x *Tfl

d) no change in the starting current

### View Answer

15. For the application requiring high starting torque and minimum starting current, the most suitable starting method will be

a) Auto transformer starting method

b) Reactance starting method

c) DOL method

d) Star-Delta method

### View Answer

16. Auto transformer method of starting has most acceptable method for the starting of the induction motor due to

a) maximum torque

b) maximum reduction of inrush current

c) variable tapping

d) all of he mentioned

### View Answer

## Set 3

1. Synchronous motors are

a) not self starting

b) self starting

c) single excited

d) none of the mentioned

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2. I. Auxiliary motor

II. Dc motor

III. induction motor

The method is/are used to perform magnetic locking

a) I,II,III

b) II,III

c) II,I

d) II

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3. Auxiliary method of starting is not possib1e due to the fact that

a) it can not be started under load

b) it can be only started under load

c) it is less efficient

d) all of the mentioned

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4. Rating of the dc motor to be used in the starting of SM, should be higher than the synchronous motor.

a) True

b) False

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5. A synchronous machine with its field winding on stator and polyphase armature winding on rotor.

At steady state, which of the following is not true for its air gap field

a) stationary w.r.t. stator

b) rotating at double the speed Ns w.r.t. rotor

c) rotating in direction opposite to rotor

d) rotating at Ns w.r.t. rotor

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6. A synchronous machine with its field winding on rotor and polyphase armature winding on stator. At steady state running condition, its air gap field is

I. stationary w.r.t. stator

II. rotating at double the Ns w.r.t. rotor

III. rotating at -Ns w.r.t. rotor

IV. stationary w.r.t. rotor.

a) IV

b) I,II,IV

c) II,IV

d) I

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7. Consider a 3-phase cylindrical-rotor alternator

A. E.m.f. generated by armature reaction lags armature current by 90°.

B. Air gap voltage leads the field flux by 90°

C. Air gap voltage lags the field flux by 90°

D. Armature reaction due to intermediate lagging p.f. is partly cross magnetizing and partly magnetizing

a) A,B

b) A,C,D

c) B,D

d) A,B,D

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8. These days alternators are designed to have larger air gaps for

a) stable parallel operation

b) higher stability limit

c) sinusoidal mmf distribution

d) all of the mentioned

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9. Consider the following statements and mark appropriately

I. In a cylindrical-rotor synchronous machine, armature flux is in phase with armature current.

II. In salient pole machine, armature flux lags the armature current.

a) I is true

b) II is true

c) I and II are true

d) None of them are true

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10. In a 3-phase cylindrical-rotor alternator, synchronous reactance is sum of mutual and leakage reactance.

a) True

b) False

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11. A 3-phase, 400V, synchronous motor is providing load at 0.8 p.f. lagging. If the field current of the motor is continuously increased, then

a) power factor increases and then decreases.

b) power factor is not affected

c) power factor decreases upto a certain value of field current and then increases.

d) power facor increases simply

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12. A synchronous machine is operating at constant load and at unity power factor.

If its excitation is increased and then it operates as

a) motor at leading p.f

b) motor at lagging p.f

c) absorber of reactive power

d) generator at leading p.f

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13. A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased, then it operates as

a) generator at lagging p.f

b) motor at lagging p.f

c) absorber of reactive power

d) generator at leading p.f

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14. The reactive power output of a synchronous generator is limited by

a) armature current and field current

b) field current and load angle

c) load angle and prime mover input

d) armature current and prime mover input

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15. Power factor of a synchronous motor varies when

a) applied voltage is varied

b) load is changed

c) supply frequency and field excitation is changed

d) all of the mentioned

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## Set 4

1. One of the most prominent component of base loads is

a) synchronous generator

b) induction generator

c) dc series generator

d) all of the mentioned

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2. ______ alternator is used in thermal stations and ______ alternator is used in hydel plants.

a) Cylindrical-rotor, salient pole

b) Salinet pole, cylindrical-rotor

c) Salient pole, Reluctance

d) Cylindrical-rotor, cylindrical-rotor

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3. Synchronous compensators are mainly employed for

a) compensating reactive power

b) compensating real power

c) improving power factor

d) compensating field flux

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4. We prefer induction motor over synchronous motor due to

a) no requirement of dc supply

b) starting problems

c) sensitive to environment

d) all of the mentioned

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5. The condition which allows the torques to be taken care for choosing a synchronous motor is/are

a) starting torque

b) pull-in torque

c) pull-out torque

d) all of the mentioned

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6. A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, its air gap field is

a) stationary w.r.t. stator

b) rotating at double the speed Ns w.r.t. rotor

c) rotating in direction opposite to rotor

d) all of the mentioned

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7. A synchronous machine with its field winding on rotor and polyphase armature winding on stator. At steady state running condition, its air gap field is

a) stationary w.r.t. stator

b) rotating at double the Ns w.r.t. rotor

c) rotating at -Ns w.r.t. rotor

d) stationary w.r.t. rotor.

### View Answer

8. Choose the appropriate

The synchronous generators used in the thermal power stations have

(i) cylindrical rotor

(ii)slip rings and brushes

(iii)laminated rotor

(iv)stator slots in the multiple of 6

(v)salient rotor

a) (i),(ii),(iv)

b) (ii),(iii),(v)

c) (i),(iii)

d) (ii),(iii),(iv),(v)

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9. The practical speed ranges for the thermal, nuclear and hydel power plants is (in rpm)

a) 3000,3000,300

b) 3000,300,300

c) 1500,1500,3000

d) 1000,500,3000

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10. Synchronous motor has been preferred for driving the loads requiring high power at low speeds.

a) True

b) False

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11. The zero power characteristics used in the Potier plot can be obtained by loading the alternator using

a) synchronous motor

b) lamp load

c) dc motor

d) induction motor

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12. Below are the statements about cylindrical rotor alternator.

A. E.m.f. generated by armature reaction lags armature current by 90°.

B. Air gap voltage leads the field flux by 90°

a) Only A is true

b) Only B is true

c) A is true, B is false

d) A and B both are true

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13. Out of the given statements about the cylindrical rotor alternator, mark the correct

A. Air gap voltage lags the field flux by 90°

B. Armature reaction mmf lags the field flux by (90°+ internal p.f. angle)

a) A is false, B is true

b) Only A is true

c) Only B is true

d) Both A and B are true

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14. The power factor of an alternator under short circuit condition will be almost near

a) zero lagging

b) zero leading

c) unity

d) depends on the type of the alternator

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15. In a 3-phase cylindrical rotor alternator

a) field mmf leads air gap flux, air gap flux leads armature flux

b) field mmf leads air gap flux, air gap flux lags armature flux

c) armature mmf leads air gap flux and air gap flux leads field flux

d) armature mmf leads air gap flux and air gap flux lags field flux

### View Answer

## Set 5

1. Steady state stability limit is defined as maximum power flow possible through a particular point without loss of stability when

a) power is increased gradually

b) power is increased suddenly

c) power is reduced gradually

d) power is reduces suddenly

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2. If the load angle is increased till 135°, the consequence will be

a) loss of synchronism

b) no alternation of synchronism

c) increase in stability limit

d) reduction in stability limit

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3. The steady state limit can be improved by

i. Increasing excitation

ii. reducing reactance

iii. using series capacitors

a) i, ii, iii

b) i, ii

c) iii only

d) ii, iii

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4. Series capacitors will improve the

a) SSSL

b) Transient stability

c) Hunting

d) Stiffness

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5. Transient stability limit is less important than SSSL

a) True

b) False

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6. (i) Transient stability is lower than SSSL

(ii) Transient disturbances are more common

a) i and ii both are true

b) i false, ii true

c) i true, ii false

d) Both are false

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7. The supply voltage to an induction motor is decreased by 10%. By what percentage, approximately, will the maximum torque decrease?

a) 5%

b) 10%

c) 20%

d) 40%

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8. In a salient pole synchronous machine the air gap is least under the middle of the pole shoe and increases outwards.

a) True

b) False

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9. If it is planned to bring an incoming alternator to the operating alternator in parallel, then which of the criteria can be ignored?

a) Prime mover speed

b) Voltage magnitude

c) Frequency

d) Phase sequence of the alternator

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10. Which one of the following is the base reason to place field on rotor in the alternator?

a) Small power in field circuit

b) Insulation of high voltage is made easy on stator than on rotor

c) Huge power in stator

d) Large current in the stator