EE Model Paper 3

8/10/2019 EE Model Paper 3

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ELECTRICAL ENGINEERING

PRACTICE SET-3

Q1.In the figure below, the current of 1 ampere flows through the resistance of:

(a) 4 ohms (b) 20 ohms (c) 30 ohms (d) 12 ohms

Q2. i!e that

" # time and space dependent electric intensit$ !ector

% # permeabilit$ of the medium

& # conducti!it$ of the medium

# permitti!it$ of the medium

'he electromagnetic wa!e euation is gi!en b$

(a) " %& % #0

(b) " %& % #0

(c) " & % #0

(d) " # #0


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Q3.In machine tool dri!e application, the speed of separatel$ e*cited dc motor is reuired to be controlled both below

and abo!e the rated speed of the motor. +hich one of the following methods is best suited for this purpose (#

armature !oltage, # field current and # field current at rated speed)

(a) (a) # !ariable

(b) fi*ed, !ariable

(c) - and !ariable, with

(d) and !ariable, with

Q4./reep in energ$ meters can be pre!ented b$

(a) sing e*tra turns on the !oltage coil.

(b) a!ing two holes on opposite sides of the disc.

(c) sing a stronger brae magnet.

(d) sing steel laminations of high permeabilit$.

Q5.+hich one of the following statements are true of a t$pe I s$stem ha!ing unit$ gain in the forward path and a unit$

feedbac

1. ositional error constant is eual to infinit$.

2. cceleration error constant is eual to 5ero.

3. 6tead$7state error to a unit step displacement input is eual to one.

6elect the correct answer using the codes gi!en below:

/odes:7

(a) 1, 2 and 3 (b) 1 and 2 (c) 2 and 3 (d) 1 and 3

Q6.'he number of elements in the power set (6) of the set

6#, 1 (2, 3)88 is

(a) 2 (b) 4 (c) 9 (d) one of these

Q7. non transistor has a beta cut off freuenc$ of a 1 ;5, and common7emitter short7circuits low7freuenc$

current of 200. Its unit$7 gain freuenc$ and the alpha cut off freuenc$ respecti!el$ are

(a) 200 ;5, 201 ;5

(b) 200 ;5, 1


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(a) "ffecti!e height.

(b) =andwidth.

(c) =eam width.

(d) Input capacitance.

Q9.n I >? processor controls the flow of information between

(a) /ache memor$ and I > ? de!ices.

(b) ;ain memor$ and I > ? de!ices

(c) 'wo I > ? de!ices.

(d) /ache and main memories.

Q10.'he most to*ic pollutant obtained b$ combustion of coal is

(a) /arbon dio*ide (b) itrogen (c) 6moe (d) $drogen

Q11.@orging iron at a temperature below the recr$stalli5ation temperature will increase the hardness of iron because

(a) Internal stresses do not appear in the iron.

(b) /r$stal defects such as dislocations are formed.

(c) 6urface shrinage from the forging operation puts pressure on the interior of the iron.

(d) 'he increases in the densit$ will cause pores and ca!ities in the metal to disappear.

Q12. set of 3 eual resistors, each of !alue connected in star across AB= in place of load as shown in the gi!en figureconsumes the same power as the unbalanced delta connected load. 'he !alue of is

(a) 33.33 ohm ( b) 100 ohm (c) 1C3.2 ohm (d) 300 ohm

Q13.ppro*imate phasor diagram of 37phase induction machines for different operating conditions are indicated in

Dist71 (with usual notations). ;atch Dist71 with the operating conditions gi!en in the Dist72 and select the correct

answer using the codes gi!en below the Dists:


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Codes:

(a) = / E

2 4 1 3

(b) = / E

2 3 4 1

(c) = / E

2 4 3 1

(d) = / E

4 2 3 1

Q14.'he armature current of a dc motor fed form a th$ristor power con!erter contains ripple. 'his ripple in the

armature current affects.

(a) /ommutating capabilit$ of the motor.

(b) ?!erload capacit$ of the motor.

(c) 'orue capabilit$ of the motor.

(d) /ontrollabilit$ of the speed of the motor.

Q15.+hich of the following limit in the reacti!e power output of a s$nchronous generator


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1. rmature current.

2. @ield current.

3. Doad angle.

4. rime mo!er input.

Q16. dc machine has, conductors per pair of poles , length of each armature conductor D, linear !elocit$ ofarmature conductor and air7gap flu*7densit$ distribution = # 6in . 'he instantaneous emfs in successi!e conductors

under one pole should be a series whole first two terms are # 6in and # 6in (.

'he last term in this series will be

(a) 6in (

(b) 6in (

(c) 6in (

(d) 6in (

Q17.=ulb turbines are

(a) igh speed turbines.

(b) igh pressure turbines.

(c) Dow head turbines.

(d) igh head turbines.

Q18. In the figure below, the !oltage across the 19 ohm resistor is


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4. @or static electric field

?f these statements:

(a) 1 and 2 are correct

(b) 2 and 3 are correct

(c) 3 and 4 are correct

(d) 1 and 4 are correct

Q20.If the commutation angle of a diode rectifier (due to source inductance effect) is %, then the inducti!e !oltage

regulation will be

(a) (b) 1 H (c) 1 (d)

Q21.+hich one of the following instruments should be used at ; in the gi!en figure of the measurement of

magnitude as well as direction of the displacement

a. ermanent magnet mo!ing coil !oltmeter

b. !acuum 'ube !oltmeter (-'-;)

( c) 'ransistor !oltmeter ('-;)

( d) hase 6ensiti!e Eetector (6E)

Q22.(w), (w) are three transfer functions whose phase !ariations are shown in the gi!en figure. 'he magnitude

!ariation with respect to freuenc$ is the same for both (w) and (w), but their phase !ariation is as indicated b$ the

cur!es labeled and / in the gi!en figure. 'he transfer function (w) is such that

(w) # (w) H (w)


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are respecti!el$

(a) ;inimum phase, all pass and non7minimum phase functions.

(b) ;inimum phase, non7minimum phase and all pass functions.

(c) ll pass, minimum phase and non7minimum phase functions

(d) ll pass non7minimum phase and minimum phase functions.

Q23.In the inter!al (0,), the euation * # cos * has

a. o solution.

b. "*actl$ one solution.

c. "*actl$ two solutions.

d. n infinite number of solutions.

Q24. 5ener diode in the circuit shown in fig. below has a nee current of J m, and a ma*imum allowed powerdissipation of 300 m+. +hat are the minimum and ma*imum load currents that can be drawn safel$ from the circuit,

eeping the output !oltageat F -

(a) 0 m, 190 m

(b) J m, 110 m

(c) 10 m, JJ m

(d) F0 m, 190 m

Q25.+hich of the following is @

(a) 40 5 (b) 400 ;5 (c) 400 K5 (d) 40 K5

Q26.'he Lenith /omputer can e*ecute 1,000,000 instructions per second. program running on this computer

performs on a!erage a one sector read and one sector writes for e!er$ 200 instructions that it e*ecutes. 'he dis dri!e

handling the I > ? transfer reuires 0.00010 seconds each to perform the read and write operations. ssuming no

o!erlap of these operation, the percent of / time spent in the wait state, is

(a) 12M (b) 3


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Q28.'he !iscoelastic beha!ior of an amorphous pol$mer will change with increasing temperature from its rigid

structure at low temperatures. 'he pol$merGs beha!ior ma$ proceed through the following stages:

1. Deather$

2. Aubber$

3. -iscous

+hat is the consecuti!e order of the stages it will pass through

(a) 1, 3 onl$ (b) 2 ,3 onl$ (c) 2 ,1, 3 (d) 1,2,3

Q29. =uchhol5 rela$ is used for

a. rotection of a transformer against all internal faults.

b. rotection of a transformer against e*ternal faults.

c. rotection of a transformer against both internal and e*ternal faults.

d. rotection and induction motors.

Q30.In a 37phase induction machine, motoring generating and braing operations tae place in the range of slip sG

gi!en b$

(a) ;otoring: 1

enerating: 1

=raing:

(b) ;otoring: 1

enerating: 0

=raing:

(c) ;otoring: s

enerating: 0

=raing:

(d) ;otoring: 0

enerating: s

=raing:

Q31.+hile operating on !ariable freuenc$ supplies, the ac motors reuire !ariable !oltage as well in order to

(a) rotect the insulation.

(b) !oid the effects of saturation.


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(c) Impro!e the commutation capabilities of the in!erter.

(d) rotect the th$ristors from d! > dt.

Q32.Euring the slip7test for determining the direct and the uadrature a*is s$nchronous reactance of an alternator,

the !oltage across the open field circuit terminals is

(a) Ec !oltage.

(b) c !oltage of suppl$ freuenc$.

(c) s !oltage of slip freuenc$.

(d) modulated !oltage with an en!elope of slip freuenc$.

Q33./onsider the following statements regarding speed control of dc motors

1. +ard7Deonard method is suitable for constant torue dri!es.

2. @ield control method facilitates speed control below base speedG.

3. rmature resistance controlG method is more efficient when compared to +ard7Deonard method.

4. @ield control method is suitable for constant horse power dri!es.

?f these statements:

a. 1 , 2 and 3 are correct

b. 1 ,3 and 4 are correct

c. 2 , 3 and 4 are correct

d. 1 and 4 are correct

Q34.=et5 law finds application in

(a) ;E s$stems

(b) 6olar cells

(c) eothermal power plants

(d) +ind mills

Q35. current of 20 flows through ammeters and = oined in series. cross the potential difference is 0.2 - and

across = it is 0.3-. @ind how the same current will be di!ided between and = when the$ are oined in parallel.

(a) # #10

(b) # #9

(c) # #12


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(d) # #1F

Q36.@or an infinite linear current, four loops are shown in the gi!en figure. 'he magnetic flu* would be the ma*imum

through the loop number.

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

Q37./onsider the following statements:7

'he diodes in a !oltage source in!erter (;c ;urr$ in!erter) should be able to

1. +ithstand a large !oltage in the re!erse direction.

2. /arr$ the commutating current e*cess of load current.

3. ro!ide the reuired re!erse bias to the outgoing th$ristor.

4. @eedbac the reacti!e current to the source

?f these statements

(a) 1, 2 and 3 are correct

(b) 1, 3 and 4 are correct

(c) 2, 3 and 4 are correct

(d) 1, 2 and 4 are correct

Q38.n integrating digital !oltmeter measures

(a) 'rue a!erage !alue.

(b) rms -alue.

(c) ea !alue.

(d) ea to pea !alue.


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Q39.'he band with of a control s$stem is the range of freuenc$ o!er which / > A (w) is greater than or eual to

(a) 1 and it depends onl$ the undamped natural freuenc$ of the s$stem.

(b) 1 and it depends onl$ on the damping factor of the s$stem.

(c) 1 and it depends onl$ on the undamped natural freuenc$ of the s$stem.

(d) 1 > and it depends on both undamped natural freuenc$ and the damping factor of the s$stem.

Q40.If at e!er$ point of a certain cur!e, the slope of the tangent euals 2* >$ the cur!e is

(a) 6traight line

(b) parabola

(c) /ircle

(d) n ellipse.

Q41.'he wa!e shape of - in figure below,

Q42. 1000 K5 carrier is simultaneousl$ modulated with 300 5, 900 5 and 2 K5 audio sine wa!es.

'he freuencies present in the output will be


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(a) 1000 K5, 300 5, 900 5 and 2 K5

(b) 1300, 5, 1900 5, 2100 5 and 4100 5

(c) 300 5, J00 5, 1200 5 and


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(c) = / E

2 3 4 1

(d) = / E

4 3 2 1

Q47. !oltmeter gi!es 120 oscillations per minute when connoted to the rotor of an induction motor. 'he statorfreuenc$ is J0 5. 'he slip of the motor is

(a) 2M (b) 2.JM (c) 4M (d) JM.

Q48./onsider the following steps:

1. Ae!ersing connections to the terminals of the capacitor.

2. /hanging the position of the capacitor from au*iliar$ winding circuit to main winding circuit.

3. Ae!ering suppl$ connection to the main winding.

4. Ae!ersing suppl$ connection to the au*iliar$ circuit.

+hile installing a new ceiling fan, if the fan motor is found to be rotating in the wrong direction, then the direction of

rotation of the motor can be corrected b$

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

Q49. 37phase fault occurs at his terminals of an unloaded alternator at an instant when the ac component in one

phase is at its ma*imum !alue. 'he !ariation in dc component during the post7fault period in that phase will depend

upon

(a) 6ub transient time constant.

(b) 'ransient time constant.

(c) ?pen7circuit time constant.

(d) rmature time constant.

Q50. dc shunt motor runs at J00 rpm of 220 -. resistance of 4.J ohm is added in series with the armature for speed

control. 'he armature resistance is 0.J ohm. 'he current to stall the motor will be

(a) 44 mp (b) J0 mp (c) 44.4 mp (d) F0 mp

Sol!"o#

1:- $d% 'here are three parallel bans which are in turn connected in series:

"ui!alent resistance of 20 ohm and 30 ohm

arallel resistors # # 12 ohms

"ui!alent resistance of F ohm, 4 ohm and 12 ohm ban # 2 ohms.


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6imilarl$ eui!alent resistance of 10 ohm and

1J ohms resistors # # F ohms.

'otal resistance of the circuit # 12 H 2 H F #20 ohms

/urrent drawn from suppl$ # # # F

/urrent through 20 ohms resistor

# F * # 3.F

/urrent through 30 ohms resistor

# F O 3.F # 2.4

"ui!alent resistance of F ohm, 4 ohm and 12 ohm ban is 2 ohm, !oltage drop

# F*2 # 12 -.

/urrent through 4 ohm resistor

# 12 > F # 2


# 12 > 4 # 3


# 12 > 12 # 1


# F * # 3.F

/urrent through 1J ohm resistor

# F O 3.F # 2.4

2:- $&%'he electromagnetic wa!e euation is gi!en b$

" O # 0

3:- $'% +ith speed is reduced and with the speed is increased abo!e normal. lso with less than speed falts, andwith greater than speed rises abo!e normal. 'o a!oid o!erloading of either the field finding or the armature winding,

through little e*pensi!e: /hoice (c) seems to be suitable.

4:- $(% /reep in the energ$ meters can be pre!ented b$ ha!ing two holes on opposite sides of the disc.

5:- $(% 1 and 2

6:- $'% 'he set has 3 members. 6o its power set has 23 # 9 members.

7:- $&% # 1 ;5


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# # 200

#

# 200 *1 ;5

# 200 ;5

nd, f #

# (1H=)

# 201 ;5.

8:- $&% 'op loading of antenna is done mainl$ to increase the effecti!e height.

9:- $(% ;ain memor$ and I > ? de!ices.

10:- $&% /arbon dio*ide and carbon mono*ide.

11:- $(% 'he forging operation distorts the euia*ed microstructure of the metals and causes the formation of cr$staldefects such as dislocations. "longated coarse grains are also produced in the direction of formation. 'hese effects of

the forging operation crate iron that is brittle.

12:- $(% Det the line !oltage be -, the power consumed b$ the load impedances of the figure shown is -P > 100+. +hen

resistors, each of !alue are connected in star, the total power drawn is

( # +.

6ince # Q # 100 ohm.

13:- $'% O 2, = O 4, / O 1.

14:- $&% 'he ripple in the armature current affects commutation capabilit$ of the motor.

15:- $&% Aeacti!e power is not dependent upon load angle and prime mo!er input.

16:- $d% 'he phase difference between two adacent conductors:

() #

'hus, # D u 6in (

17:- $'% =ulb turbines are low head turbines.

18:- $&% since !oltage across 19 ohm resistance is


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'his 20 ohm resistance is in parallel with J ohm resistance gi!ing eui!alent resistance of

# 4 ohms

ence total resistance circuit

# 1H4 # J ohms.

6ince total resistance across de # 19H20 # 20 ohms.

/urrent through this branch is J

-oltage across de # J*20 #100 -.

# !oltage across bc.

ence, current through J O ohm resistance be # 100 > J # 20

'otal current through ab # 20HJ #2J .

6ince total resistance of the circuit is J ohm,

-oltage " # 2J*J # 12J -.

19:- $'% @or free space are each 5ero. 'hus statements 3 and 4 are correct.

20:- $d% # R

+here is the rectifier output !oltage when the dela$ angleQ and B, the commutation angleQ are both 5ero.

ssuming to be 5ero

# (1 H cos B).

/hange in !oltage due to source inductance effect is

@ractional regulation is

#

21:- $d% ; should be able to detect phase re!ersal if not strictl$ phase sensiti!e. hase sensiti!e detector can well ser!e

the purpose.

22:- $&% It can be minimum phase, all pass and non7minimum phase function.

23:- $(% the point of intersection of the line $#* and the cur!e $#cos (*), will be the root (s). If $ou draw the graph it will

be clear that the$ meet onl$ once in the gi!en inter!al (0,). 6o, e*actl$ one root

DDI'"A:

/onsider the function f (*) # * O cos (*) f (0) is 071 # 71, a negati!e number @ (0) is O (71) # H1, a positi!e number.

6o, the function should ha!e odd number of roots in the inter!al (0,). lso it can not ha!e infinitel$ man$ roots as cos


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(*) oscillates in (71, 1), while *, increases monotonicall$ and so infinite solution is impossible. ence = is the correct

answer.

24:- $'% I #

# 3 > J0

# 0.3 > J

# 0.0F

# F0 m

6o ma*imum load current (F07J) m#m

ow, # > - # 300 > F # J0 m

min # F0 m O J0 m #10 m.

25:- $(% 'he range for ltra igh @reuenc$ is 300 ;5 to 3 5.

26:- $d% 'he wait time can be calculated in the following manner:

'ime to read 1 sector 0.0010

'ime to write 1 sector 0.0010

'ime to e*ecute 200 instructions 0.0002

'otal program c$cle time 0.0022

+ait time # 0.0020 >0.0022S 100M


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28:- $d% 'he pol$mer goes from a leather$ stage, to a rubber$ and then a !iscous stage. In the leather$ stage the

pol$mer can be deformed readil$ but it cannot regain its shape uicl$ if the stress is remo!ed. In the rubber$ stage

the pol$mer can regain its original shape uicl$. In the !iscous stage the pol$mer deforms e*tensi!el$ b$ !iscous flow.

29:- $&% =uchholt5 rela$ is used for protection of a transformer against all internal faults.

30:- $&% motoring: 1 s 0

enerating: 0 s 71

=raing: s

31:- $&% !oid the effects of saturation.

32:- $'% /learl$, the !oltage induced in the field winding would ha!e a freuenc$ directl$ related to the relati!e speed of

the rotor and the s$nchronousl$ rotating armature mmf.

33:- $d% 6tatements 1 and 4 onl$ are correct.

34:- $d% =et5 law finds application in wind mills.

35:- $(% Aesistance of ammeter is

# # 0.01ohm

Aesistance of ammeter = is

# # 0.1J ohm

+hen the ammeters and = are oined in parallel,

# I # 20 *

# 12

# I # 20 *

# 9 .

36:- $(% ll the loops ha!e eual areas. = at an$ distance r from the wire is > r. @or an$ rectangular loop of height h (in

the direction of the wire) and width w ( the wire), the

@lu* is Kh in

+here a is the distance of the nearside from the wire.

'hus, for 1, # I in


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@or 2, # 2I in

@or 3, # 2I in

@or 4, TU # I in

V # K I in (1H, W # 2I in (1H

X # K I in (1H, U # I in (1H

'he long terms do not change b$ significant amount. 'hus, should be of highest value.

37:- $'% 2, 3 and 4 are correct.

38:- $&% n integrating digital !oltmeter measures true a!erage !alue.

39:- $d% 'he bandwidth of a control s$stem in the range of freuenc$ o!er which

(Yw) Z

Is greater than or eual to 1 >. 'his is as per definition. @urther, bandwidth depends on both7 the undamped

natural freuenc$ and the damping ratio. @or instance, the characteristic euation of a second order s$stem

ma$ be e*pressed as

sP H 2 s H P #0

+here is the undamped natural freuenc$ of oscillation and is the damping ratio. lso it can be shown that 2

is the bandwidth. 'hus the bandwidth is dependent on both and

40:- $d% 6lop (d$ > d*) # (72* > $)

Bd$ # 72* d*

Integrating both sides, $P > 2 # (72*P > 2) H / i.e., *P >/ H $P > bP #1,


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"llipse, *P > aP H $P > bP # 1

It is clear that the cur!e is an ellipse.

41:- $&% ?ne c$cle time # 20 m6

'ime for source !oltage to become 4.1 - during positi!e half c$cle is gi!en b$

4.1 # 10 6in 0.314t, t in m6

'hus, t # 1 > 0.314 4.1 > 10

# 1.34J m6.

'he diode = conducts now ( is alread$ forward biased ) and the !oltage across the load is (106in . 314t O 4.1)

-. 6imilar situation occurs in the negati!e half c$cle when Lener = is forward biased and Lener a!alanches

when source !oltage becomes 4.1 -. 'hus the !oltage across 10 7ohm is gi!en in figure (a)

42:- $d% 300 5 # 0.3 5Q 900 5 # 0.9 Kh5

@reuencies present in the output will be 1000

I.".


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47:- $'% circuit # slip *

# s * J0

s # * 100M # 4M

48:- $d% 2, 3 and 4.

49:- $d% will depend on armature O time constant.

50:- $&% the motor is to be stalled, i.e., the motor speed is reduced to 5ero b$ adding more and more load on the shaft.

nder that condition

# # 44 .

EE Model Paper 3

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