objective questions.doc rk

41
ution (Set 4) Electrical Objective Questions With Answers: 1) Stringing Charts are useful: a) In design of the Transmission Towers b) For Finding the SAG in the Conductors c) In Design of Insulator String d) To Find the distance between the Towers 2) Which is the topmost conductor in the HV transmission: a) R-Phase Conductor b) B-Phase Conductor c) Y-Phase Conductor d) Earth Conductor 3) The String Efficiency of a string of suspension insulators is dependent on: a) Size of the Insulators b) Number of Insulator discs in the String c) Size of the Tower d) None of the above 4) The Voltage across the various identical discs of a string of suspended insulators is different due to: a) Because of different surface leakage current of each discs b) Because of different series capacitance of each discs c) Because of different Shunt capacitance to ground for each disc d) Because of different series and shunt capacitance 5) String Efficiency of an Insulators can be increased by: a) Increasing the number of insulator discs in the string b) Decreasing the number of insulator discs in the string c) correct grading of insulators of various capacitance d) Changing the design orientation of the string to horizontal

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Page 1: Objective Questions.doc Rk

ution (Set 4) Electrical Objective Questions With Answers:

1) Stringing Charts are useful:a) In design of the Transmission Towersb) For Finding the SAG in the Conductorsc) In Design of Insulator Stringd) To Find the distance between the Towers

2) Which is the topmost conductor in the HV transmission:a) R-Phase Conductorb) B-Phase Conductorc) Y-Phase Conductor d) Earth Conductor

3) The String Efficiency of a string of suspension insulators is dependent on:a) Size of the Insulatorsb) Number of Insulator discs in the Stringc) Size of the Towerd) None of the above

4) The Voltage across the various identical discs of a string of suspended insulators is different due to:a) Because of different surface leakage current of each discsb) Because of different series capacitance of each discsc) Because of different Shunt capacitance to ground for each disc d) Because of different series and shunt capacitance

5) String Efficiency of an Insulators can be increased by:a) Increasing the number of insulator discs in the stringb) Decreasing the number of insulator discs in the stringc) correct grading of insulators of various capacitanced) Changing the design orientation of the string to horizontal

6) If the frequency of transmission system is increased then the string efficiency: a) Increaseb) Decreasesc) Remain unchangedd) None of the above

7) The use of Gaurd Ring is to:a) Equilises the voltage division between the insulator discsb) Increases the voltage division between the insulator discs

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c) Decreases the voltage distribution among the insulator discsd) None of the above

8) The purpose of Gaurd Ring in the transmission system is to:a) Reduce the earth capacitance of the lowest unitb) Increases the earth capacitance of the lowest unitc) Reduces the transmission lossesd) None of the above

Answers:

(1) b (2) d (3) b (4) c (5) c (6) c (7) a (8)a

1)In overhead lines for transmitting power we generally use:a) Copper Conductorsb) Aluminum Conductorsc) ACSR conductorsd) Galvanized Steel Conductors

2) ACSR Conductors implies:a) Aluminum Conductors Steel Reinforcedb) Anodised Core Steel Reinforcedc) All Conductors Surface Reinforcedd) None of These

3) ACSR Conductors are used in overhead transmission lines in place of copper because:a) Economy factorb) They are light weightc) All of thesed) High Tensile Strenght

4) The function of steel wire in the ACSR conductors is to:a) Compensate for Skin Effectb) Provide additional mechanical strenghtc) Carry large currentsd) To Reduce Inductance

5) Which material is used for manufacturing of ground wire:a) Aluminumb) Steel wirec) Cast irond) Galvanised Steel

6) Effect of Temperature rise in overhead lines is to:

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a) Increases the SAG and decreases the Tension of linesb) Decreases the SAG and Increases the Tension of lines c) Increase in both SAG and Tension of the linesd) Decreases in both the SAG and Tension of the lines

7) SAG depends on what factors in transmission lines:a) Span lengthb) tension in the conductorsc) Weight of the conductor per unit lenghtd) All the above

8) In transmission system between two supports, due to SAG the conductors take the shape of:a) Catenaryb) semi circulec) Parabolad) Hyperbola

Answers:

(1) c (2) a (3) c (4) b (5) d (6) a (7) d (8) a

DC Machines Objective test Questions 1.In DC Generator the critical resistance refers to:a) Armatureb) Fieldc) Loadd) CommutatorAnswer BRemember:If resistance of field is beyond critical resistance Generator will not start

2.In DC Generator the residual magnetism will be of the order:a) 2.5%b) 10%c) 15%d) 20%Answer ARemember:Residual magnetism is the magnetism left in field poles of dc generator. This helps in starting self excited dc generator

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3.Sparkless commutation can be achieved by employinga) Interpolesb) Compensating windingc) High resistance corbon brushesd) All the aboveAnswerDRemember:All the above three methods will be used to reduce sparking due to commutation

4.Comutator in DC machine acts as:a) Full wave rectifierb) Half wave rectifierc) Controlled full wave rectifierd) Controlled half wave rectifierAnswerARemember:Commutator converts pulsating AC (sinusoidal) to unidirectional pulsating dc

5. In DC machine, commuataor convertsa) dc to acb) ac to dcc) both ac to dc and dc to acd) None of the aboveAnswerCRemember:Current flowing through the armature windings is ac. Therefore in dc motor commutator coverts dc supply to ac to armature and in dc generator comutator converts ac armature current to dc output

6. Which type of emf is induced in the dc generatora) Dynamicallyb) Staticc) Electrostaticd) MagenticAnswerARemember:In dc generator field produced by the magnets are stationary and moving conductors cut the stationary magnetic field.Static Induced emf: Transformer (eg) where conductors are stationary and moving magnetic field cuts stationary conductors

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7. If a current carrying conductor is placed in the uniform magnetic field with its plane perpendicular to the direction of magnetic induction then,a) The net force and torque on the coil are zerob) net force is zero and torque is finitec) net force is finite and torque is zerod) the net force and torque are finiteAnswerARemember:Plane perpendicular to magnetic induction means angle theta = 0. Because angle theta is angle between conductor and line perpendicular to magentic axis. Hence induced emf e=BLV sin(theta)=0. No force exist hence the torque cancels out and zero.

8. In DC machinea) The current and electromagentic force in armature conductors are alternating while those at the terminals are uni-directionalb) The current and emf in armature conductors are uni directional while those at the terminals are alternatingc) The current and the emf in armature conductors and at terminals are unidirectionald) The emf in armature conductors and at the terminals is alternating while current is uni directionalAnswerARemember:emf and armature current is alternating in nature. However because of commutator they are uni directional at the machine terminals

9. The induced voltage in a single loop reverses:a) Once in each revolutionb) Once in each half revolutionc) Once in each one quarter revolutiond) Once in each two revolutionsAnswerBRemember:Induced emf will reverse for half cycle. This is the reason we get complete sine wave for one revolution of the conductor

10. The yoke of the dc machine is made of:____ magnetic materiala) softb) hardc) nond) very goodAnswer

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ARemember:In DC machine yoke also serves purpose of allowing field magnetic flux. Therefore soft iron is used to reduce the losses

. Impedance relay is used for:a) Phase faultsb) Earth faultc) both phase fault and earth faultd) none of the above

2. Series capacitors are used in transmission lines for:a) Compensate the voltage dropb) Reduce the line lossesc) Limit the short circuit currentd) Improve load power factor 

3. The surge impedance of a 3phase500kV transmission line is 500ohms. The surge impedance loading of the line isa) 500MWb) 1000MWc) 1500MWd) 2500MW

4. Bundled conductors used in EHV transmission to reduces thea) Surge impedance of lineb) Voltage drop of the linec) corona loss of the lined) I2R loss of the line

5. Which bridge is used to determine the frequency:a) Anderson bridgeb) De Sauty bridgec) Wein bridged) Campbell bridge 

6. Which plant is used as base load planta) Thermal plantb) Hydro plantc) Nuclear plantd) Gas plant

7. Which one of the following is zero as applied to electomagnetic fields:a) grad div Ab) div grad Vc) div curl Ad) curl curl A 

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8. An electric circuit consists of 12 branches and 8 nodes will havea) 4 loop equationsb) 5 loop equationsc) 7 loop equationsd) 8 loop equations 

9. dv/dt protection for scr can be achieved bya) R and L in series to SCRb) R and L in parallel to SCRc) R and C in series to SCRd) R and C in parallel to SCR 

10. The current drawn by a 220V d.c motor with back emf of 210V and armature resistance of 0.4 ohms is:a) 4 A b) 25A c) 8A c) 16A 

11.The emf induced in the primary of the transformer:a) Leads the flux by 90o

b) In phase with the fluxc) Lags the flux by 90o

d) Is in phase apposition with the flux. 

12. Induction motor under no load will have power factor of:a) 0.80 lagb) 0.70 lagc) 0.50 lagd) 0.20 lagl

 Answers:

(1) a   (2) a   (3) a  (4) c(5) c   (6) c   (7) c  (8) b(9) d (10) a (11) c (12) d

2) Wave winding is employed in a dc machine of: (IES 2006)a) High current and low voltage ratingb) Low current and high voltage ratingc) High current and high voltage ratingd) Low current and low voltage rating

3) The resultant flux density in the air gap of a synchronous generator is the lowest during: (IES 2006)a) Open circuitb) Solid short circuit

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c) Full loadd) Half load

4) If the load of an Induction motor is increased from no load to full load, its slip and the power factor will respectively (IES 2006)a) decrease, decreaseb) decrease, increasec) increase, decreased) increase, increase

5) A single phase Induction motor is running at N rpm. Its synchronous speed is Ns. If its slip with respect to forward field is 's', what is the slip with respect to the backward field is: (IES 2006)a) sb) -sc) (1-s)d) (2-s)

6)  Match the following: (IES 2003)List I                                                   List II A. DC Motor                        1. Circle DiagramB. DC Generator                  2. V-CurvesC. Alternator                        3. Open circuit characteristicsD. Induction Motor                4.Speed-Torque characteristics

Codes:         A          B          C         D a)      4           3          1         2b)      3           4          2         1c)      4           3          2         1d)      3           4          1         27)  A smaller air gap in a polyphase induction motor helps to: (IES 2004)a) reduces the chances of crawling b) Increases the starting torquec) reduces the chances of coggingd) reduce the magnetising current

8) If the supply voltage of the induction motor is reduced by 10%. By what percentage approximately will the maximum torque decreases? (IES 2004)a) 5%b) 10%c) 20%d) 40% 

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 Answers:

(1) b (2) b (3) b (4) d (5) d (6) c (7) d (8) c

) Match the Following   ( IES- 2003)

      List I                                           List II A. Transformer                           1. Slip TestB. DC Motor                               2. Blocked Rotor TestC. Alternator                               3. Sumpner's Test D. Induction Motor                      4. Swinburne's Test

Codes:         A          B          C         D a)      3           4          1         2b)      4           3          2         1c)      3           4          2         1d)      4           3          1         2

2) Possible three to three phase transformer connection for parallel operation is: ( IES- 2002)a) Delta-Star to Delta-Starb) Delta-Delta to Delta-Starc) Star-Star to Delta-Stard) Delta-Star to Star-Delta

3) Stepper Motors are widely used for  ( IES- 2002)a) Very high power requirementb) Very high speed operationc) Very low speed operationd) Control system applications

4) Armature torque of a d.c motor is a function of which of the following factors ( IES- 2003)

1. Speed2. Field Flux3. Armature Current4. Residual MagnetismSelect the correct answera) 2 and 3b) 1 and 4c) 3 and 4d) 1 and 2

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5) The dummy coils in the DC machine are useful toa) Increase the efficiency of the machineb) Improve the commutationc) Reduce the armature reaction d) Maintain mechanical balance

6) The synchronous reactance is the ( IES- 2003)a) Reactance due to armature reaction of the machineb) Reactance due to the leakage fluxc) Combined reactance due to leakage flux and armature reactiond) Reactance either due to armature reaction or leakage flux

7) The crawling in the induction motor is due to  ( IES- 2003)a) Improper design of the stator laminationsb) Low voltage supplyc) Improper design of rotor laminationsd) Harmonics developed in the motor

8) In an Induction motor, when the number of stator slots is equal to an integral multiple of rotor slots  ( IES- 2003)a) There must be a discontinuity in the torque slip charcteristicsb) A high starting torque will be availablec) The maximum torque will be highd) The machine may fail to start

Answers:

(1) a (2) a (3) d (4) a (5) d (6) c (7) d (8) d

1. MHO  relay is used for the protection of: (a)a) Long distance Transmission line b) Medium length lines c) Short transmission lines d) None of the above

2. Reactance Relay isa) Voltage restrained directional relayb) Directional restrained over current relayc) Voltage restrained over current relayd) None of the above

3. Which relays are doesn't affect by power swings

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4. When a transmission line connected in parallel to other transmission linea) Stability decreases and fault current decreasesb) Stability increases and fault current decreasesc) Stability decreases and fault current increasesd) Stability increases and fault current increases

5. Software interrupts in 8085 microprocessor:

6. Number of address and Data lines in 8085 microprocessor

7. When Halt instruction is executed in microprocessor

8. RL circuit was given and asked to find the value of Inductor

9. Circuit with resistor values are given and asked to solve the equivalent resistance (quite easy circuit given)

10. Small circuit was given and asked to solve the current flowing through the resistor (simple circuit)

11. In the presence of earth capacitance value of  transmission lines ___ (Increases)

12. L-G fault phase difference between positive and negative sequence currents

13. For complete protection of 3 phase line ___ ( Two phase and One earth fault relay is sufficient )

14. During slip test in synchronous motor the voltage across the field wingdings is ___ (zero)

15. Reactive power in synchronous machine is limited by ___ (field current and power angle )

16. For changing the direction of rotation in dc motor armature is used because __

17. Which type of DC motor has negative voltage regulation __

18. Auto transformer voltage transformation ___ (HV-LV)/HV

19. Asked to find out linear system from different equations ___

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20. SCR turns off when __ (current falls below holding current )

21. AC voltage converter ___

22. BP register pointing data in __ (Stack Segment )

23. Question related to 8259 and ICW

24. Semi Closed or completely closed rotor bars are employed to __

25. Asked to find phase margin for an open loop transfer function

26. Matrix A, B,C and D is given asked to find transfer function

BHEL ET general engineering paper 2011:

1. Chlorine acts as bleaching agent in the presence of ___

2. Satellites receive power from ___ (Solar cells)

3. Rotometer is used to measure the ______ (flow rate of fluids and gases)

4. For ideal gas PV/RT is ____ (Unity)

5. Strain Gauge is used to measure ____ (pressure)

6. Type of flow when Reynolds number of fluid is high _____ ( Turbulent)

7. When Iron ball, Wooden ball and cork ball is dropped in to liquid which will reach the bottom first__ (Iron ball)

8. Hook's law is applicable upto the _____ (proportionality limit)

9. Moderator used in nuclear reactor______ (To slowdown the fast neutrons by collision)

10. Fuel used in fast breeder reactor_____ (PU 239 )

11. Which of the following is not an electromagnetic wave____ (Ultra sonic waves)

       a) X ray b) gamma rays c) Cathode rays d) Ultra sonic waves

12. Compression ratio of petrol engine is ____

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13. Coplanar forces are _______ (forces acting along the same plane)

14. What is Bakelite ____

15. Bernoulli principle explains about the _____ (energy conservation)

16. When the Length of the simple pendulum is Doubled what happens to energy (Question is something like that) ___

     a) E b) E/2 c) 4E d) 8E

17. LVDT is used to___

18. One question is on Fraunhofer lines?

19. Above curie temperature magnetic materials act as__

20. Synchronous motor has similar construction to ___ (Alternator)

21. Which of the motor is best used for speed control ___ (DC Shunt motor)

22. Variables that define the properties of the gas__ (Question  is something like that)

      a) Pressure b) Volume c) Temperature d) All the above

23. Why boron is used in Stainless steel___ (To reduce corrosion)

24. Definition of Center of Buoyancy

25. Which is hardest __

 a) Cast Iron b) Mild iron c) other options

26. Why rain drop is spherical__ (Surface Tension)

27. Which of the following has low conductivity __

    a) Copper b) Aluminum C) Steel d) Air

28. Which of the following cannot be used as Permanent magnet __

29. One simple question on angular velocity___30. Magnetic north pole in uniform magnetic field align towards___ (Geometric south of the earth)31. All electrical machines are __ (electro mechanical conversion devices)

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196. The materials in order of decreasing eddy current loss will be

(A) iron, wood, aluminium

(B) iron, aluminium, wood

(C) aluminium, iron, wood

(D) wood, aluminium, iron.

 

Get Answer:(Show)

 

197. For a 5 kW DC motor the number of slots per pole should be

(A) 4

(B) 8

(C) 12

(D) 16.

 

Get Answer:(Hide)

B

 

198. In a synchronous generator in order to eliminate the fifth harmonic the chording angle should be

(A) 9°

(B) 18°

(C) 27°

(D) 36°.

 

Get Answer:(Show)

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D

 

199. Inter poles in DC machines are provided to reduce

(A) sparking

(B) armature reaction

(C) iron loss

(D) efficiency.

 

Get Answer:(Hide)

A

 

200. Skewing in the slots of an induction motor is provided to reduce

(A) iron loss

(B) noise

(C) harmonics

(D) temperature rise.

 

Get Answer:(Show)

C

 

201. Sometimes a reactor is connected in series with a transformer to

(A) improve regulation

(B) control fault current

(C) improve efficiency

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(D) improve power factor.

 

Get Answer:(Hide)

B

 

202. DC motor yoke is generally made of

(A) wood

(B) copper

(C) aluminium

(D) steel.

 

Get Answer:(Show)

D

 

203. For the same rating, the cost of an induction motor as compared to that of a DC motor is

(A) more

(B) less

(C) same

(D) nearly the same.

 

Get Answer:(Hide)

B

 

204. In case of electrical machines, the intermittent rating as compared to its continuous rating is

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(A) more

(B) less

(C) same.

 

Get Answer:(Show)

A

 

205. For the use of mush windings in 3φ induction motors, the slot should be

(A) semi-closed

(B) open

(C) closed

(D) either (a) or (b).

 

Get Answer:(Hide)

A

 

206. A hunting sound is produced in a synchronous motor when

(A) load fluctuates

(B) supply frequency varies

(C) both (A) and (B) above

(D) none of the above.

 

Get Answer:(Show)

C

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207. The transformer noise is mainly because of

(A) cooling oil

(B) sinusoidal current

(C) magnetic flux

(D) all of the above.

 

Get Answer:(Hide)

C

 

208. Stampings in transformers are provided to reduce

(A) hysteresis loss

(B) eddy current loss

(C) copper loss

(D) all of the above.

 

Get Answer:(Show)

B

 

209. Which loss occurs in the yoke of a DC machine ?

(A) iron loss

(B) copper loss

(C) heat loss

(D) no loss.

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Get Answer:(Hide)

D

 

210. The losses occurring in the rotor of an induction motor are less than those in the stator because of

(A) small diameter of rotor

(B) less rotor frequency

(C) slot skewing

(D) none of the above.

 

Get Answer:(Show)

211. In case of transformers, with increasing frequency

(A) copper losses reduce but efficiency increases

(B) copper losses increase but efficiency decreases

(C) both copper losses and efficiency increase

(D) copper losses remain unaffected while efficiency increases.

 

Get Answer:(Hide)

D

 

212. The regulation of a transformer is least affected by changes in frequency at

(A) leading power factor

(B) lagging power factor

(C) unity power factor

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(D) all of the above.

 

Get Answer:(Show)

C

 

213. In case of induction motor, with increase in supply voltage, which of the following increases ?

(A) Power factor

(B) Slip

(C) Torque

(D) All of the above.

 

Get Answer:(Hide)

C

 

214. In most AC machines, it is usually a standard practice to use

(A) fractional slot winding With full-pitch coils

(B) fractional slot winding with chorded coils

(C) integral slot winding with chorded coils

(D) integral slot winding with full pitch coils.

 

Get Answer:(Show)

B

 

215. In a transformer iron losses vary as __________ of voltage

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(A) inverse

(B) inverse square

(C) square

(D) cube.

 

Get Answer:(Hide)

C

 

216. In case of distribution transformers, at fractional loads

(A) with increase in voltage efficiency decreases

(B) with increase in voltage efficiency increases

(C) with decrease in voltage efficiency decreases

 

Get Answer:(Show)

A

 

217. In case of transformers regulation varies as

(A) inverse of voltage

(B) square of voltage

(C) inverse square of voltage

(D) voltage.

 

Get Answer:(Hide)

B

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218. In a transformer, with change in frequency

(A) copper losses increase

(B) copper losses decrease

(C) copper losses remain unchanged.

 

Get Answer:(Hide)

C

 

219. Distribution transformer has core losses

(A) > copper losses

(B) = copper losses

(C) ∞ copper losses

(D) = 1/2 copper losses.

 

Get Answer:(Show)

C

 

220. If a synchronous motor fails to start, the probable cause could be

(A) low voltage

(B) too much load at starting

(C) single phasing

(D) any of the above.

 

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Get Answer:(Show)

D

 

221. In case a synchronous motor starts but fails to develop full torque, the probable cause could be

(A) low excited voltage

(B) reverse field winding

(C) open or short circuit

(D) any of the above.

 

Get Answer:(Hide)

D

 

222. If a DC machine gives shock the probable cause could be

(A) armature field coils or brush holders earthed

(B) weak or leaky insulation

(C) loose earth wire

(D) all of the above.

 

Get Answer:(Show)

D

 

223. If a DC motor stops after running for some time, the probable cause could be any of the following EXCEPT:

(A) Weak or no field

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(B) Brushes ahead of neutral

(C) Insufficient power supply

(D) Insufficient torque developed.

 

Get Answer:(Hide)

B

 

224. If fuse blows at the starting of a DC motor the probable cause could be

(A) low capacity of the fuse

(B) overload

(C) short circuit in the starter resistance

(D) any of the above.

 

Get Answer:(Show)

D

 

225. Sound in a DC motor may be due to

(A) unequal resistance of the armature and field coils

(B) loose fittings of the field core with yoke or frame

(C) improper fitting of the side covers

(D) any of the above.

 

Get Answer:(Hide)

D

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1. In induction motors, there is large decrease in maximum power factor when the dispersion coefficient is __________

 

Get Answer:(Show)

increased

 

2. As the number of poles induction motor becomes large, it becomes __________ to obtain higher power factor.

 

Get Answer:(Show)

difficult

 

3. In induction motor when the length of the air gap is increased, the magnetizing current of the motor increases while the short circuit current __________

 

Get Answer:(Hide)

remains unchanged

 

4. In induction motor with the increase in number of poles, the ideal short circuit current decreases, magnetizing current remains unchanged and the dispersion coefficient __________

 

Get Answer:(Show)

increases

 

5. In dc machines the plane passing through the axis of the armature and through center of contact of the brushes is known as __________ plane.

 

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Get Answer:(Hide)

commutating

 

6. The plane passing through the axis of the armature perpendicular to the magnetic field of the generator at no load is known as __________ plane.

 

Get Answer:(Show)

normal neutral

 

7. When a transformer is operated on a supply frequency higher than its rated frequency, its kVA rating will become.............

 

Get Answer:(Hide)

higher

 

8. The operating speed of a salient pole machine is __________ as compared to that of cylindrical pole machine.

 

Get Answer:(Show)

more

 

9. Per unit no load current of induction motor is __________ that of the transformer.

 

Get Answer:(Hide)

more than

 

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10. Field systems of the cylindrical rotor alternators are wound in the __________

 

Get Answer:(Show)

slots of the rotor

 

11. In dc machines the angle between commutating plane and normal neutral plane is called angle of __________

 

Get Answer:(Hide)

lead

 

12. __________ is a medium which being at a lower temperature then the primary coolant than, removes heat from primary coolant in a heat exchanger.

 

Get Answer:(Show)

secondary coolant

 

13. An insulating material should have __________ dielectric loss.

 

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low

 

14. Liquid insulating materials should not __________

 

Get Answer:(Show)

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evaporate

 

15. The cause of hum in the transformers is assigned to __________

 

Get Answer:(Hide)

magnetostriction

 

16. __________ are prepared by high temperature of natural clay with certain inorganic matters.

 

Get Answer:(Show)

ceramics

 

17. Current density for armature winding of a dc machine is in the range of __________ A/mm2 .

 

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4 to 7

 

18. A good insulating material should be unaffected by __________

 

Get Answer:(Show)

moisture

19. By adding silicon to iron __________ properties are improved.

 

Get Answer:(Hide)

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magnetic

 

320. Thickness of laminations normally used in transformers is the range __________ mm.

 

Get Answer:(Show)

0.35 to 0.5

 

21. Distribution transformers are invariably __________ transformers.

 

Get Answer:(Hide)

step down

 

22. The shaft of induction motor is generally made of __________

 

Get Answer:(Show)

mild steel

 

23. When a ferromagnetic material is magnetized, its physical dimensions change slightly. This phenomena is known as __________

 

Get Answer:(Hide)

magnetostriction

 

24. The materials exhibiting magnetostriction find applications in __________ oscillators.

 

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Get Answer:(Show)

high frequency

 

25. Winding surrounds the core in case of __________ type transformer.

 

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core

 

26. Disadvantage of taking higher current density in the design of electrical machine is that of __________

 

Get Answer:(Show)

high copper loss

 

27. A distribution transformer should have __________ iron losses.

 

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low

 

28. Transformer core are generally made of __________

 

Get Answer:(Show)

silicon steel

 

29. An ideal insulating material should have __________ heat conductivity.

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good

 

30. The specific gravity of cable paper is __________

 

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0.68 to 0.71

 

31. Asbestos is hygroscopic and contains around __________ moisture at room temperature.

 

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14%

 

32. Asbestos cement is used in __________ devices.

 

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arcing

 

33. Neoprene is a homo polymer of __________

 

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2-chlorobutadiene

 

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34. Polytetra flouroethylene is commercially known as __________

 

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Teflon

 

35. Salient pole type alternators are used when the speed of prime mover is __________

 

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low

 

36. Core surrounds the winding in case of __________ type transformer.

 

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shell

 37. In electrical machines, in order to prevent the conductor from being thrown out due to centrifugal force, a __________ is provided in the slots.

 

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wooden wedge

 

38. Porcelain is a kind of __________

 

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ceramic

 

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39. Ceramics are generally hard, strong and __________

 

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dense

 

40. Silica is the main constituent of __________ refractories.

 

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acid

 

41. Titanate ceramic has high dielectric constant and is used in __________

 

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capacitors

 

42. __________ is an inorganic material prepared by fusion of different metallic oxides.

 

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Glass

 

43. Wax is largely used as __________ compound.

 

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sealing

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44. Presence of moisture in liquid insulating materials generally __________ the dielectric strength.

 

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decreases

 

45. Flux density for distribution transformer is taken in the range of __________ to __________ tesla.

 

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(1.0 , 1.3)

 

46. In case CRGO steel is used instead of hot rolled steel in electrical machines, its efficiency will be __________

 

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higher

 

47. Power factor of a 3 phase induction motor is generally closer to __________

 

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0.8

 

48. Transformer oil should have __________ permittivity.

 

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high

 

49. A varnish consists of oil, resins, solvent and __________

 

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dryer

 

50. Plasticizers are added to PVC to control the __________ of the insulating material.

 

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flexibility