two wires a and b of the same material and length l and 2l have radius r ad 2r resp

7/27/2019 Two Wires a and B of the Same Material and Length L and 2L Have Radius r Ad 2r Resp

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1) Two wires A and B of the same material and length L and 2L have radius r ad 2r resp. the ratioof their specific resistance will be

a) 1:1b) 1:2c) 1:4d) 1:82) Three parallel resistive branches are connected across a dc supply. What will be the ratio of

branch current I1:I2:I3if the branch resistance are in ratio R1:R2:R3::2:4:6?

a) 3:2:6b) 2:4:6c) 6:3:2d) 6:2:4

3) A certain network consists of a large number of ideal linear resistance R and two constant idealsources. The power consumed by R is P1when only one source is active and P2when second

source is active. If both sources are active simultaneously then the power consumed by R is

a) P1 P2b) c) ( ) 2d) ( P1 P2)2

4) Kirchhoff law is not applicable to the circuit witha) Distributed parametersb)

Lumped parameters

c) Passive elementsd) Nonlinear elements

5) In the interconnection of ideal sources it is known that 60V source is absorbing power. What isthe value of current source i?

a) 10Ab) 13Ac) 15Ad) 18A

+20V -

+60V

-

12 A

i


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6) In a balanced wheat stone bridge if the position of detector and source are interchanged, thebridge will still remain balanced. This inference can be drawn from

a) Reciprocity theoremb) Duality theoremc) Compensation theoremd) Equivalence theorem

7) The most important advantage of using electrical energy in form of AC isa) The lower construction cost per KW of ac generationb) Conductor of smaller cross section is requiredc) Lesser insulation is requiredd) Transformation of voltage is possible in case of ac only

8) A 2 terminal network consist of one of the RLC element. The element is connected across the acsupply and current through it is (i) Amp. When an inductor is inserted in series between the

source and that element, the current through the element is 2(i) Amp. What is the element?

a) Resistorb) Inductorc) Capacitord) Cannot be a single element

9) The power factor of following will be zeroa) Resistiveb) Capacitivec) Inductived) Both b and c

10)In ac series RLC circuit the voltage across R and L is 20V, voltage across L and C is 9V and voltageacross RLC is 15V. What is the voltage across C?

a) 7Vb) 12Vc) 16Vd) 21V

11)When the Q factor of circuit is high thena) Power factor of the circuit is highb) Impedance of the circuit is highc) BW is larged) None of the above

12)In series and parallel resonant circuit increase in resistance would causea) Increase in BW of both circuit


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b) Decrease in BW of both circuitc) Decrease in BW in series and increase in parallel circuitd) Decrease in BW in parallel and increase in series circuit

13)If the step response of initially relaxed circuit is known then ramp response can be obtained bya) Integrating the step responseb) Differentiating the step responsec) Integrating the step response twiced) Differentiating the step response twice

14) A sinusoidal voltage of voltage source 50 V with an impedance of 10+20j is connected to a loadZLwhich is variable in both power and reactance. Match list 1 and 2 for maximum power

transfer and select the correct answer

List 1 List 2

A Load impedance 1 62.5

B Total impedance 2 10+20jC Current 3 2.5

D Maximum power 4 20

5 10-j20

6 2.5-j2.5

15)A rotating electrical machine having its self-inductance of both stator and rotor winding,independent of rotor position will definitely not develop

a) Staring torqueb) Synchronizing torquec) Hysteresis torqued) Reluctance torque

16)In dc machine the winding loss is propositional toa) Supply voltageb) Square of supply voltagec) Square of flux densityd) Square of armature speed

17)Wave winding is employed in a dc machinea) High current and low voltage ratingb) low current and high voltage rating

Codes A B C D

a 5 2 3 4

b 5 4 3 1

c 2 4 6 1

d 2 5 6 4


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c) High current and high voltage ratingd) low current and low voltage rating

18)welding generator will havea) lap windingb) wave windingc) either lap or wave windingd) none

19)Due to magnetic saturation, the flux per pole in a dc machine without brush shifta) Increase in both generator and motor with loadb) decrease in both generator and motor with loadc) increase in generator but decrease in motord) increase in motor but decrease in generator

20)The interpoles in dc machine have tapering shape in order toa) Reduce the overall weightb) Reduce saturation in the interpolec) Economics of the material for interpole and their windingd) Increase in the acceleration of commutation

21)Consider the following statement about the commutating poles which are fitted on most largedc shunt motors

a) The commutating poles are placed in geometrical neutral plan and their number is usuallyequals to the number of main poles

b) The windings on the commutating poles is connected in series with the shunt fieldwindings on the main poles

c) The polarity of the commutating poles must be that of next of the main pole further aheadd) The commutating poles neutralize the reactance produced in the coil undergoing

commutation.

i. 1,2,3 are correctii. 1,4 are correct

iii. 2,3,4 are correctiv. 1,2,4 are correct

22)The voltage at the terminal of dc series generator running at rated rpm and no load will bea) More than rated voltageb) Full rated voltagec) Very small voltaged) Zero


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23)A dc shunt generator is supplying a load of 1.8kw at 200 V. its armature and field resistance are0.4 and 200 respect. What is generated emf?

a) 190b) 196c) 204d) 210

24)Consider the following statementi. In dc series generator, full load voltage is more than no load voltage

ii. In separately excited dc generator full load voltage is more than no load voltageiii. In dc shunt generator full load voltage is less than no load voltage

a) 1,2,3 are correctb) 1,2 are correctc) 2,3 are correctd) 1,3 are correct25)Which of the following has rising VI characteristic

a) Seriesb) Shuntc) Compoundd) None

26)A dc series motor is employeda) As a booster to maintain constant voltage at the load end of the feederb) For supplying transaction loadc) For supplying industrial load at constant voltaged) For battery charging

27)The main factor that lead to unstable parallel operation of flat or over compound dc generatora) The rising voltage characteristicb) Unequal series field resistancec) Unequal speed regulation of their prime moverd) The drooping characteristic

28) The dc motor which can provide zero voltage regulation at full load without any controller isa) Seriesb) Shuntc) Cumulative Compoundd) Differential Compound

29)T is the load torque of a dc series motor having linear magnetization and negligible armatureresistance. Speed of the motor is


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a) Inversely proportional to square root of Tb) Directly proportional to square root of Tc) Inversely proportional to square of Td) Directly proportionalto square of T

30)A differentially compound dc motor is running at rated speed. If the series field winding of themotor get short circuited, the speed of the motor will

a) Remain unalteredb) Increasesc) Decreasesd) Zero

31)The main disadvantage of Hopkinson test is thata) It need large powerb) It need two identical machinec) No account is taken for charge in iron loss due to flux distortion on full load conditiond) All of the above

32)In relation to dc machine match the followingList 1 List 2

A Developed power 1 N

B torque 2 EBIA

C Generated emf 3 EB/

D Speed 4 IA

34) If the rated dc voltage is applied instead of ac to primary of a transformera) Secondary of transformer will burnb) Primary of transformer will burnc) Secondary voltage will be excessively larged) No secondary voltage

35)The low voltage windings of a 400/230 v single phase 50 hz Transformer to be connected to a25 hz supply. In order to keep the magnetization current at the same level in both case the

voltage at 25 hz should be

a) 230vb) 460vc) 115v

Codes A B C D

A 2 4 1 3

B 3 1 4 2

C 2 1 4 3

D 3 4 1 2


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d) 65v36)In transformer which of the following is valid statement

a) In open circuit test , copper loss are obtained while in SC test core loss are obtainedb) In OC test current is drawn at high power factorc) In a SC test current is drawn at zero power factord) In OC test current is drawn at lower power factor

37)The desirable property of transformer core material area) Low permeability and low hysteresis lossb) high permeability and high hysteresis lossc) high permeability and low hysteresis lossd) Low permeability and high hysteresis loss

38)Sludge formation in transformer oil is due to which of the followinga) Ingress of dust particles and moistureb) Appearance of small fragment of paper varnish cotton and other organic material in oilc) Chemical reaction of transformer oil with insulating materiald) Oxidation of transformer oil

39)Possible three to three phase transformer connection for parallel operationa) - to -b) - to c) - to d) to

40)Which one of the following is the primary reason for placing field winding on rotor in analternator

a) Small power in field circuitb) Insulation of high voltage is made easy on stator than on rotorc) Large power in statord) Large current in stator

41)In a large synchronous generator the damper winding is provided fora) Absorption of energy of oscillation when operating in parallel with another alternatorb) Suppuration of spontaneous hunting when supplying power to a transmission with high

resistance/reactance ratio.

c) Providing a low resistance path for current due to unbalancing of voltages.d) All of the above

42)The salient pole rotor are not suitable for high speed turbo generator due toa) Excessive bearing friction


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b) Undesirable mechanical oscillationc) High centrifugal forces and winding lossd) large eddy current losses

43)in a synchronous alternator which has emf closer to sin wavea) concentrated winding in full pitch coilb) concentrated winding in short pitch coilc) distributed winding in full pitch coild) distributed winding in short pitch coil

44)the magnitude of leakage flux of synchronous alternator depend ona) magnitude of armature currentb) phase angle between armature current and terminal voltagec) air gap thicknessd) both a and b

45) armature reaction of a synchronous generator supplying power at rated voltage with zeropower factor lagging is

a) Magnetizingb) Demagnetizingc) Cross Magnetizingd) Both a and b

46)The leakage reactance of a three phase alternator is determined bya) OC test and zero power factor testb) zero power factor test and slip testc) OC and SC testd) SC and slip test

47)Higher the applied voltagea) Higher will be the stator fluxb) Higher will be pull in torquec) Lower will be stator torqued) Lower will be pull in torquee) Both a and bf) Both a and d

48)An infinite bus bar hasa) Constant voltageb) Constant frequencyc) Infinite voltaged) Infinite current


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e) Infinite frequencyf) Both a and b

49)An inductor motor can run at synchronous speed if its operateda) No loadb) Full loadc) With emf injected in the rotord) On voltage higher than rated voltage

50)In comparison to resistance start induction motor the permanent capacitor motor isa) More expensiveb) Has better power factorc) Has better starting torqued) Both a and be) All of the above

51)In shaded pole induction motor locked rotor current is ____________ full load currenta) Less thanb) Equal toc) Slightly more thand) Several times the

52) Hysteresis motor isa) Self startingb) Constant speed motorc) Does not need dc excitationd) Both a and be) All of the above

53)List 1 List 2

A Unity power factor 1 Fully demagnetizing

B Zero power factor lagging 2 Fully magnetizing

C Zero power factor leading 3 Cross magnetizing

D Intermediate lagging 4 Partially cross magnetizing and

Partially cross demagnetizing

Codes A B C D

A 3 1 4 2

B 3 1 2 4

C 1 3 2 4

D 1 3 4 2


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55)Which one of the temperature below which certain material are anti ferromagnetic and abovewhich are paramagnetic

a) curie temperatureb) Neel temperaturec) Transition temperatured) Weiss temperature.

56)In diamagnetic material the effect of an applied magnetic field is thata) Net reduction in flux densityb) Induced magnetization is in opposite to the applied fieldc) Net dipole moment is induced in the materiald) All of the above

57)Susceptibility of diamagnetic material is1) Negative2) Positive3) Depend on temperature4) Independent of temperature

a) 1,3b) 2,4c) 1,4d) 2,3

58)The converse of magnetostriction effect isa) Villari effectb) Curie effectc) Skin effectd) See back effect

59)Blinking of fluorescent tube may be removed bya) Replacement of starterb) Checking of all connectionc) Change of ballast tappingd) Any of the above turn by turn

60)Draw in system of laying underground cable has drawback ofa) Higher costb) Reduced current carrying capacityc) Requirement of much deeper and wider trenchesd) Repair replacement alternation or addition difficultye) All of the above except (d)


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61)Which of following distribution system is preferred for good efficiency and high economya) Single phase, 2 wire systemb) 2 phase, 3 wire systemc) 3 phase. 3 wire systemd) 3 phase 4 wire system

62)Stranded conductor usually has central wire around which there are successive layer of6,12,18,24 wires. For n layers the total number of individual wires is

a) 3n(n+1)b) 2n(n+1)c) 3n(n+1)+1d) 2n(n+1)+1

63)The non-uniform distribution of voltage across the unit in a string of suspension type insulatoris due to

a) Unequal self-capacitance of the unitb) Non uniform distance of separation of the unit from the tower bodyc) The existence of stray capacitance between the metallic junction of the unit and the tower

body

d) Non uniform distance between the cross arm and the unit.64)3 phase transmission line has its conductor at the corner of an equilateral triangle with side 3m.

the diameter of each conductor is 1.63 cm. the inductance of the line per phase per km is

a) 1.232mhb) 1.182mhc) 1.093mhd) 1.043mh

65)Which the following is correcta) Surge impedance is the impedance at the time of breakdown of voltageb) Surge impedance and characteristic impedance for a transmission line are samec) Surge impedance is the impedance of transmission line when corona take place.d) None of the above.

66)A lossless radial transmission line with surge impedance loadinga) Take negative VAR at sending end and zero VAR at receiving endb) Take positive VAR at sending end and zero VAR at receiving endc) Has flat voltage profile and unity power factor at all point along it.d) Has sending end voltage higher than receiving end voltage and unity power factor at

sending end.


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67)Capacitance grading of cable meansa) Use of dialectical in different concentrationb) Introduction of capacitance at various length of cable to counter the effect of inductancec) Use of dialectical of different permittivity,d) Grading according to capacitance per km length of the cable.

68)Bulk power transmission over long HVDC lines are preferred an account ofa) Low cost of HVDC terminalb) No harmonics problemc) Minimum line power lossd) Simple protection

69)HVDC transmission there are predominanta) Voltage harmonics on dc side and current harmonics on ac side of converterb) Current harmonics on dc side and voltage harmonics on ac side of converterc) Current harmonics only on the dc side of converterd) Voltage harmonics only on the ac side of converter.

70)Which of the following are the effect of increase the reverse bias across PN junctiona) Decrease in junction capacitance of the diodeb) Increase in carrier generation currentc) Increase in carrier recombination in the depletion layer.

i. 1 aloneii. 2 and 3

iii. 1 and 2iv. 1,2,and 3 are correct

71)A step recovery diodea) Has extremely short recovery timeb) Is mainly used as a harmonic generatorc) Conducts equally well in both directiond) Is an ideal rectifier of high frequency signal.

72)List 1 List 2

A Boltzmann constant 1 Farad/meter

B Permeability of free space 2 Cm2/volt-sec

C Permittivity of free space 3 Henry/meterD mobility 4 Cm2/second

5 Electron volt/kelvin

Codes A B C D

A 5 2 1 4


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73)

List 1 List 2

A Donor energy level 1 At the middle of forbidden

energy gap

B Fermi level of p type

semiconductor at room

temperature

2 Close to the conduction band

C Acceptor energy band 3 Very close to the valence bandD Fermi level in intrinsic

semiconductor

4 Close to the valence band

74) In an RC coupled common emitter amplifier

a) coupling capacitance affect the higher frequency response and bypass capacitance affect the low

frequency response

b) both coupling and bypass capacitance affect HF response

c) both coupling and bypass capacitance affect LF response

d) coupling affect Hf response and bypass capacitance affect LF response

B 1 2 5 4

C 5 3 1 2

D 1 3 5 2

Codes A B C D

A 4 3 2 1

B 2 1 4 3

C 4 1 2 3

D 2 3 4 1


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two wires a and b of the same material and length l and 2l have radius r ad 2r resp

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