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Q.l - Q.30 CARRY ONE MARK EACH

1. Fig. Q 1 shows the waveform of the current passing through an inductor of resistance 1 n and inductance 2 H. The energy absorbed by the inductor in the first four seconds is

2.

3.

(a) 144 J 6A ---------(b) 98 J (c) 132 J

0 t (d) 168 J 2S 4S

A segment of a circuit is shown in Fig.Q2. VR = sv, v c = is given by Q (a) 3 - 8 cos 2t (b) 32 sin 2t (c) 16 sin 2t (d) 16 cos 2t

I-(a) trdy

y

+ z.

I -(c) 2trdy

The Venn impedance

z, X

I -(d)-x 2trd

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5. Two infinite strips of width w m in x direction as shown in Fig. Q5, are carrying forward and return currents of +I and -I in the z direction. The strips are separated by a distance of x m . The in du eta nee per unit I eng th of the configuration is measured to be L H/m . If the distance of separation between the

6.

7.

strips is now reduced to

is ~ (a) 2L H/m fx (b) L/4 H/m

(c) L/2 H/m (d) 4L H/m y

A single phase transformer has a maximum efficie0 o+> at full load and unity power factor. Efficiency at half load at the same e factor is (a) 86.7% (b) 88.26% (c) G (d) 87.8% Group I lists different ap pi i cations and ~I I i sts the m a tors for these app li cations. Match the application wi it~~ o c sui tab I e motor and choose the right combination among the ch.,aices ~ after

Group I Group II Perm anent magnet de motor P Food m1xer!/t

Q Cass~tte a c er R Dam e ump

2 Single phase i ndu cti on motor 3 Universal motor 4 Three phase i nd ucti on motor 5 DC series motor

SE0 -......\ 6 Stepper motor

( ~~ 6+ R- 4 S- 5 (b) P- 1 Q- 3 R- 2 S- 4 - 3 Q- 1 R- 2 S- 4 (d) P- 3 Q- 2 R- 1 S- 4

I oad. A cap a a tor 1 s now connected across the I oad to com pi etel y nu lllfy the md uct1 ve current. For th 1 s oper atmg con d1 t1 on. (a) the field current and fuel mpu t have to be reduced (b) the field current and fuel input have to be in creased (c) the field current has to be increased and fuel input I eft unaltered (d) the field current has to be reduced and fuel input left unaltered

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9. Curves X and Y in Fig. Q9 denote open circuit and fu 11-1 oad zero power factor ( zpf) characteristics of asynchronous genera tor. Q is a point on the zpf char acteri sti cs at 1. 0 p. u. val tage. The vertical distance PQ in Fig .Q. 9 gives the val tage drop across

(a) Synchronous reactance (b) Magn eti zing reactance (c) Potier reactance (d) Leak age reactance

10. supply curve was

Core loss (c) Stray load loss

11. Bundled conductors are main I y w s voltage overhead tran sm i ssi on I i nes to (a) reduce transmission line I s (b) increase mechanical~ the line (c) reduce corona~..,. v (d) reduce sag A power syste si s of 300 buses out of which 20 buses are generator buses, 2 5 bus :h ones with reactive power support and 15 buses are the ones with fixe ~t capacitors. All the other buses are I oad buses. It is

P"~"-~ 'l"d How'"''''' "' iog "'"""-"Ph"" m eth si zt of the Newton -Raph son Jacobi an matrix is

(b) 540x540 (c) 555x555 (d) 554x554

12.

13 two appropriate auxiliary components of a HVDC transmission system e following P~ D.c. line inductor

A.C. line inductor Reactive power sources

S Distance relays on D.c. line T Series capacitance of A. C. line (a) P and Q (b) P and R (c) Q and S (d) SandT

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14. A round rotor generator with internal voltage E 1 = 2.0 p .u. and X = 1.1 p.u. is connected to a round rotor synchronous motor with internal val tag e E 2 = 1. 3 p. u. and X = 1. 2 p. u. The reactance of the line connecting the genera tor to the motor is 0. 5 p. u. when the genera tor sup pi i es 0. 5 p .u. power, the rotor angle difference between them achines will be (a) 57.42 (b) 1 (c) 32.58 (d) 122.58

15. The mterrup tmg t1 me of a a rcUI t breaker 1 s the pen od between the 1n st '~ (a) InitiatiOn of short CirCUit and the arc extinCtiOn On an Opening De~' (b) energ1 zmg of the tn p c1 rcu 1 t and the arc ex tm ct1 on on an open 1 op at1 on (c) i ni ti ati on of sh art circuit and the parting of primary arc cofiJ!t~ (d) energizing of the trip circuit and the parting of primary ar~ts

16. The of t" source val tage e MOSFET is

17.

v.~

(a) 0 (b) -90 (c) +90 (d)180

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19. Fig.Q19 shows a 4 to 1 MUX to be used to implement the sum S of a 1-bit full adder with input bits P and Q and the carry input C;n. Which of the following combinations of inputs to 10, It. 12 and 13 of the MUX will realize the sum S? (a) (b) (c) 10 =13 =C.,;11 =12 =C;n (d) 1o =13 =C;,;11 =1z =C;n

4 to 1 MUX

Ia

It F lz 11 s1 Sa

20. When a program is being Counter contains

21.

22.

(a)

(b) (c) (d)

state of the system

(a) [0.271] 1.100

been

(c)x=2.4 (d) X = -2

I oop contrail er has the foil owing transfer

(c) a> Kb (d) a< Kb

starts w1th an 1n 1 t1 al cond 1 t1 on of [ ~] WIthout any ex tern a I given by [ 8~2r e~' l The

at the end of 1 second is given by

(b) [0.135] (c) [0.271] 0.368 0.736

(d) [0.135] 1.100

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24. A Mang ani n swamp resistance is connected in series with a moving coil ammeter consisting of a m iII i -ammeter and a sui tab I e shunt in order to

25.

26.

27.

(a) minimize the effect of temperature variation (b) obtain I arge deflecting torque (c) (d)

reduce the size of the meter m 1 n1 m 1 ze the effect of stray m agn et1c fie Ids

i nstru men t is maximum when the op eratm g field of the mstru men n tray fields are (a) perpend icu I ar (c) inclined at 60

(b) parallel CJ (d) inclined at 30

A reading of 120 is obtained when a standard indl:':'>ra~ connected in the circuit of a Q-m eter and the variable capacitor i~~ a value of 30 0 pF. A I ossless capacitor of unknown value c. is the con cted in parallel with the variable capacitor and the same readilli ined when the variable capacitor is readjusted to a value of 200 p T a ue of c. in pF is (a) 100 (b) 200 .(.. 00 (d) 500

Fig. Q2 7 shows a th yri star with st~d terminations of an ode (A), cathode (K), gate (G) and the differen ns named J1, J2 and J3. When the thyristor is turned on and conducti~

0~ ; ~ '

J3

J2

Jl

N

(b) J 1 and J 3 are forward biased and J2 is reverse biased (c) J 1 is forward biased and J2 and J3 are reverse biased (d) J1, J2 and J3 are all forward biased

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28. Fig.Q28 shown a MOSFET with an integral body diode. It is em played as a power switching device in the ON and 0 FF states through appropriate control. The 0 N and 0 FF states of the switch are given on the V os-1 s pI an e by

29.

D

v ..

Is Is

-?r---+-*'"-vs

(a) Fig.A

Fig.A

Is

CJ &'(j ' '" ~

F1g.C ..1__ '7j -?r---+---Vos

F1g.D

t>.~.B (c) F1g.C (d) F1g.D torq~mes 1n a de motor and the control methods su1table for the ven specti vely in Group II and Group I

Group I Group II p Fie I d Control 1 Below base speed Q Armature Control 2 Above base speed

3 Above base torque 4 Below base torque

(a) P- 1; Q- 3 (b) p- 2; Q- 1 (c) P- 2; Q- 3 (d) p- 1; Q- 4

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30. A fully contrail ed natural commuted 3 -phase bridge rectifier is operating with a firing angle oc= 3 0. The peak to peak voltage ripple ex pressed as a ratio of the peak output de val tage at the output of the converter bridge is

(a) 0.5 (b) ../3 2

Q.31- Q.90 CARRY TWO MARKS EACH

31. In the circuit of Fig .Q31, the magnitudes of VL and Vc are twice that of VK. The inductance of the coil is

32.

33.

(a) 2.14 mH (b) 5.30 H (c) 3.18 mH (d) 1.32 H

In Fig.Q32, the potential difference betwe (a) 12 V (b) 10 v (c) -6 V (d) 8 v

In Fig.34, the value of R is (a) 100. (b) 180. (c) 240. (d) 120.

4n

40V

(d) ../3 -1

jan

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35.

36.

37.

38.

A balanced delta connected I oad of ( 8+ j 6) 0. per phase is connected to a 400 v, 50 Hz, 3-phase supply lines. If the input power factor is to be improved to 0.9 by connecting a bank of star connected cap ad tors the required k VAR of the bank is (a) 42.7 (b) 10.2 (c) 28.8 (d) 38.4

(a) 2V (b) 4V (c)

The h -parameters for a two-port [EI] = [hll ~12 ] [ ~1 l For the two-port n etw I2 h21 22 2 4n

is given by ~ lz ' (a) 0.125 E,~ IE, (b) 0.167 (c) 0.625 (d) 0.25

A point charge of +~n is din a space with a permitivity of8.85 x 10-12 F/m as shown in Fig .Q . tential difference VPQ between two points P and Q at distances of 400 0 mm respectively fi'om the point charge is (a) 0.22 kV zomm

(b)~225 Q (c) -2 +

lnC 40mm

all el pi ate cap a a tor has an electrode area of 10 0 m m 2, w1 th a spacmg of 0.1 m m between the electrodes. The d 1 el ectn c between the pi ates 1 s a1 r WIth a perm1tt1v1ty of 8.85x10-12 F/m. The charge on the capacitor 1s 100 v. the stored energy 1n the capac1 tor 1 s (a) 8.85 pJ (b) 440 pJ (c) 22.1 nJ (d) 44.3 nJ

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40. A composite parallel pi ate capacitor is made up of two different di electric materials with different thickness (tt and t2) as shown in Fig.Q40. The two different d i electric materials are separated by a conducting foil F. The val tag e of the conducting foi I is (a) 52 v

lOOV

(c) 67 V e,z=4'tz lmm (d) 33 v ov

(b) 60 V e, 3t O.Smm F ~

41. Flg.Q41 shows an 1deal smgle-phase transformer. The pnmary andg ry

lz

It

E,

E, Ez

Ez lz L_ __ _.

Ez I,

Fig.A ...... \ + F1g.B F1g.C F1g.D

~., (b) F1g. B (c) F1g. C (d) F1g. D nduct load test on a de shunt motor, 1t 1s coupled to a generator wh1ch 1s cal to the motor. The field of the generator 1s also connected to the same

sup pi y source as the motor. The armature of the generator 1 s connected to a I oad res1 stance. The armature res1 stance 1 d 0 .0 2 p .u. armature react1 on and m echan 1cal I asses can be neg I ected. W1 th rated val tage across the motor, the I oad resistance across the generator is adjusted to obtain rated armature current in both motor and generator. The p.u. value of this load resistance is (a) 1.0 (b) 0.98 (c) 0.96 (d) 0.94

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43. Fig.Q43 shows a 6-Y connected 3-phase di stri bu ti on transformer used to step down HV the voltage from 11000 V to 415 V line-to- A._---..... ---.. line. It has two switches 5 1 and 52. Under normal conditions 5 1 is closed and 52 is open. Under certain special con di ti ons 5 1 is open and 52 is closed. In such a case the B..,_---e-4>--

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(a) (b)

DC machines P.S Q.U

Synchronous machines Q.T P.T

Induction machines R.U

R.S (c) P.S R.U Q.T (d) R.S Q.U P.T

exc1ted, each would produce a smuso1dal mmf d1stnbut1on~a1r ap w1th peak values F s and F, respect1 vely. The rotor m m f I ags sta m a space angIe a at any 1n stant as shown 1n F1 g .Q 46. Thus, half of stat nd tor surfaces will form one pole w1th the other half form mg the second . Further, the direction of torque acting on the rotor can be cl:ckwis0u~r-clockwise.

Stator mmf axis

Rotor mmf axis

torque.

Stator Surf ace CDA Rotor Rotor Surface Surface cda Torque is forms cda forms forms

South Pole North Pole South Pole Clockwise

North Pole North Pole South Pole Counter clockwise

North Pole South Pole South Pole North Pole Counter clockwise

South Pole North Pole South Pole North Pole Clockwise

4 7. A 4-p ole, 3-ph ase, double I ayer winding is housed in a 3 6-sl ot stator for an ac machine with 60 phase spread. Coil span is 7 slot pitches. Number of slots in which top and bottom I ayers belong to different phases is

fh\ 1 Q fr\ 1'? t ri\ n

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48.

49.

50.

51.

52.

A 3 -phase Inductor Motor is driving a constant torque I oad at rated val tage and frequency. If both voltage and fi'equency are halved, following statements relate to the new con di ti on if stator resistance, I eakag e reactance and core I ass are ignored. P The difference between synchronous speed and actual speed remains same Q The a1r-gap flux rem a1ns same R The stator OJ rrent rem ams same S The p.u. slip rem ams same

(a) All (b) P, Q and R (c) Q, RandS ~~an

A s1ngle phase 1nduct1on motor w1th only the mam w1ndmg e~ould exh1b1t the foil owm g response at synchronous speed (a) Rotor rurrent is zero ~ .. + (b) Rotor rurrent is non-zero and is at slip frequj"-J (c) Forward and backward rotating fie Ids are eq I (d) Forward rotating field is more than th~ otating field A de series motor driving an elec ~a~nVes a constant power load. It is running at rated speed and rateGI ~ the speed has to be brought down to 0.25 p.u. the supply voltage ha e a roxim ately brought down to (a) 0.75 p.u. (b) 0.5 . (c) 0.25 p.u. (d) 0.125 p.u.

The ABCD parameters f~e overhead transmission line are A= D =0.9LO B = 2DOL900. an ~~3 L90S. At no-load condition a shunt inductive reactor is connfbd a receiving end of the line to I i mit the receiving end val tage to be e a t sending end val tage. The ohmic value of the reactor is (a) oo n ~b) 2000 n (c) 105.26 n (d) 1052.6 n

A s~r 0 t magnitude travels along a lossless cable towards its junction 1!. 1 tical I ossless overhead tr ansm i ssi on I in es. The i nd uctan ce and the ca c1 - of the cable are 0.4 m H and 0.5 ~F per km. The inductance and itance of the overhead transmission lines are 1.5 m H and 0.015 ~F per km . ...... ~ gnitude of the voltage at the junction due to surge is ~~ 36.72 kV (b) 18.36 kV (c) 6.07 kV (d) 33.93 kV

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53. A d c distribution system is shown in Fig. Q5 3 with I oad currents as marked. The two ends of the feeder are fed by voltage sources such that v,.- VQ = 3V. the

54.

55.

value of the voltage Vp for a minimum voltage of 220 V at any point along the feeder is

v. Vo

O.ln R 0.15n s o.zn p Q ~

lOA 20A 30A 15A 0 (a) 225. 89 v (b) 222.89 v (c) 220.0 v 0 28.58 v

A 3-phase, 11-kV generator feeds power to a c~ar>._ r~nity power factor load of 100 MW through a 3-phase transmissio 1 :"~ne-to-line voltage at the terminals of the machine is maintained sta at 11 kV. The per unit positive sequence impedance of the line~ MVA and 11 kV is j 0 .2. The I i ne-to-1 in e val tag e at the I oad te~ asu red to be I ess than 11 k v. The total reactive power to be inject at rm i nal s of the I oad to in crease the line-to-line voltage at the load t Is t 1 kV is (a) 100 MVAR (b) 10.1 R (c) -100 MVAR (d) -10.1 MVAR

The bus Impedance matr~ s power system is given by j0.3435 j~.2 . . 3 j0.22771 jO .2860 jO .3 8 586 jO .2414

Zbus =

jO .227 ' . 4 jO .2209 j0.2791 j0.2720 '0, 0.2791 j0.2209

A branch hav1 m pedance of JO .20. 1s connected between bus 2 and the

""~" '"' "'"" '""- '"' '" "" '"h bO> 1m pod'"~ mtr'" of the m ne~ork are respect1 vel y. and JO .4586 0. (b) JO .1260 0. and J0.0956 0.

. 0. and JO .0956 0. (d) JO .1260 0. and J0.1630 0.

MVA, 6.6-kV, 3-phase alternator 1s connected to a 3-phase transm 1Ss1on I i ne. The per unit positive sequence, negative sequence and zero sequence impedances of the alternator are j0.1, and j0.04 respectively. The neutral of the alternator is connected to ground through an i nd ucti ve reactor of j 0 .0 5 p .u. The per unit positive, negative and zero sequence impedances of the tr ansm i ssi on line are j0.1 and j0.3 respectively. All per unit values are based on the machine ratings. A solid ground fault occurs at one phase of the far end of the tr ansm i ssi on I i ne. The val tage of the alternator n eu tr al with respect to ground during the fault is (a) 513.8 V (b) 889.9 v (c) 1112.0 V (d) 642.2 v

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57. Incremental fuel costs (in same appropriate unit) for a power plant consisting of three generating units are

58.

IC1 =20+0.3P1 IC2 = 30 +0.4P2 IC3 = 30

where P1 is the power in MW generated by unit i, for i = 1,2 and 3. Assum t all the three units are operating all the tim e. Minimum and maximum d~ o each unit are 50 MW and 30 0 M w resp ecti vel y. If the pI ant is op ti n~n econom 1 c I oad d 1sp atch to supp I y the total power demand of 70 0 0 ower generated by each un1t Is----------------( a) Pt = 242.86 MW; P~ 157.14 MW; and P3 = 300 MW r ~ (b) P1 = 157.14 MW; P~ 242.86 MW; and P3 = 300 MW~ (c) P1 = 300.0 MW; P~ 300.0 MW; and P3 = ~ (d) P1 = 233.3 MW; P~ 233.3 MW; and P3 = oH A I i st of relays and the power system com pone ~tected by the rei ays are g1ven 1n Group I and Group II respective'?$~ correct match fi'om the four ch 01 ces g1 ven bel ow:

Groupl pll p

Q Under fi'equ ency r rb 1n es R D1fferent1al rlljl Busbars S BuchhdJoz r I 4 Shunt capacitors

5 AI ternators

r>., 6 Transm1ss1on lines (a) P- 6 Q-~ S- 1 (b) P- 4 Q- 3 R- 2 S- 1 (c) P - :;+R- 1 S- 6 (d) P- 6 Q- 4 R- 5 S- 3

rk. The maximum power that could be delivered by the generator is 2.0 . three phase fau It occurs at the terminals of the generator which reduces genera tor output to zero. The fau It is cleared after tc second. The original

network is then restored. The maximum swing of the rotor angle is found to be 8m = 110 electrical degree. Then the rotor angle in electrical degrees at t = tc is (a) 55 (b) 70 (c) 69.14 (d) 72.4

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60. A three-phase alternator generating unbalanced voltages is connected to an un balanced load through a 3-phase tr ansm i ssi on I i ne as shown in Fig. Q60. the neutral of the alternator and the star point of the I oad are solidly grounded. The phase voltages of the alternator are Ea = lOLO'V, Eb = lOL- 90'V, Ec = 10L12Dv. The positive sequence component of the I oad current is

=

61.

62.

E. jl.On jl.On

~

E. jl.On j2.0n ~

jl.On j3.on ~---.----~ ~

(c) + 7 v and- 4 v (d) + 4 v and- 7 v

4V

:;-y- 4VT lOkn f

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64. The circuit of Fig .Q64 shows a 555 Timer IC connected as an astable m ultivibrator. The value of the capacitor C is 10 nF. The values of the resi stars R A and Rs for a frequency of 10 kHz and a duty cycle of 0.7 5 for the output val tag e waveform are R. (a) RA= 3.62 kO., Rs = 3.62 kO. (b) RA=3.62 kO., Rs = 7.25 kO. Re (c) RA=7.25 kO., Rs = 3.62 kO. (d) RA=7.25 kO., Rs= 7.25 kO.

The si m pi i fi ed block diagram of a 10 -bit A/D con ve e~r d~l slope integrator type is shown in Fig.Q65. The 10-bit counter at t t clocked by a 1 MHz clock. Assuming n egl i gi bl e timing overhead for c I ogi c, the maximum

65.

66.

frequency of the analog signal that can be con ted sing this A/D converter is app rox i m a tel y

Input sample to be converted

-Reference de input

(a) 2kHz

(c) 11 (d) 15

10-b~ Counter

dock

1 MHZ z

Serial infpu:::t:...._~L-1 _l.,O,-L1,__L_o,J

Digital output

(d) 250Hz

bit pattern 1010.

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68. An X-V flip flop, whose Characteristic Table is given below is to be im plem en ted using a J-K flip flop

69.

70.

~

X 0 0 1 1

This can be done by making (a) J = X, K = Y

y 0 1 0 1

Q t 1

Q. Q. 0

(b) J = (c) J = Y, K = X (d) J = 0 + A memory system has a total of 8 memory dhipt:ac~ with 12 address lines and 4 data lines. The total size of the memory s ~

flj The followmg pro~1tten for an 8085 microprocessor to add two bytes located at mem6~dF 1FFE and 1FFF

'(..1 LXI H, 1FFE MOV B, M

INR L

MOV A,M ADD B INR L MOV M,A XOR A

On com pI etion of the execution of the program, the result of addition is faun d (a) in the register A (b) at the memory address 1000 (c) at the memory address 1 FO 0 (d) at the memory ad dress 20 00

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71. A control system with certain ex d tati on is governed by the following math em ati cal equation

72.

73.

74.

d2x +..!. dx + ....!.._ x = 10 + se- + 2e-sr dt2 2 dt 18

The natural time constants of the response of the system are (a) 2s and Ss (b) 3s and 6s (c) 4s and Ss (d) 1/3

(c) 6% (d) 33%

+ 3 S+ 15

system shown in

(d) -6 and 10

de motor in the form of a

(b) [-F -1~] (d) [-1~ -~]

as follows

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7 5. The I oop gain G H of a closed system is given by the foil owing expression K

s(s+2)(s+ 4) The value of K for which the system just becomes un stab I e is (a) K = 6 (b) K = 8 (c) K = 48 (d) K = 96

76. The asymptotic Bode plot of the transfer function ~is given in s 1+-a

error in phase angle and dB gain at a frequency of oo= 0. 5 a are

20 log K

G dB 20db/decade a

(a) 4.9, 0.97 dB (c) 4.9, 3 dB (d) 5.7, 0.97 dB

77. is shown in Fig. Q 77. The transfer function

Integrator y(t)

1 (b) 1

(c) 1 (d) 1

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78. The items in Group I represent the various types of measurements to be made with a reasonable accuracy using a suitable bridge. The items in Group II rep resent the v ari ou s bridges av ai I able for this purpose. Select the correct choice of the item in Group II for the corresponding item in Group I from the following

Group I Group II P Resistance in them illi-Ohm range 1 Wheatstone B ridge Q Low values of Capacitance 2 R Com pari son of resistances which are nearly equal 3 Schering Bridg S I nd uctan ce of a coi I with a I arg e time constant 4 wien's Bridr ~

5 Hay's Brid~

79.

6 Ca~~t~ Bridge

(a) P- 2 Q- 3 R- 6 S- 5 (b) '('!!"2 'f-1 R- 4 S- 5 (c) P- 2 Q- 3 R- 5 S- 4 ~~- 3 R- 2 S- 6

A rectifier type ac voltmeter cons1 sts ~ e res1 stance R., an 1 deal full wave rect1fi er b n d ge and a PMMC 1n str t a shown 1n F1 g. Q 79. The 1n tern a I res1 stance of the mstru men t 1s 10 full-seale deflect1 on 1 s produced by a de current of 1 m A. The value Re ired to obtain full scale deflection with an ac voltage of 100 V (rm s) the input terminals is

ac inpu

If PMMC millimeter

tm eter reads 40 0 W when its current coil is connected in the R phase and p essure coil is connected between this phase and the neutral of a

symmetrical 3 -phase system supplying a balanced star connected 0. 8p. f. i nd ucti ve I oad. The phase sequence is R VB . What wi II be the reading of this wattmeter if its pressure coi I alone is reconnected between the B and Y phases, all other connections remaining as before (a) 400.0 (b) 519.6 (c) 300.0 (d) 692.8

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81.

82.

83.

84.

~

The inductance of a certain moving -iron ammeter is expressed as 2

L = 10 + 30-~ ~JH, where e is the deflection in radians fi"om the zero position. 4

The control spring torque in 25x10"6 Nm/radian. The deflection of the pointer in radian when the meter carries a current of SA, is (a) 2.4 (b) 2.0 (c) 1.2 (d) 1.0~

A 500 A/5 A, 50 Hz current transformer has a bar pnmary. The second bu n 1s a pure res1stance of 1 n and 1t draws a current of s A. If thea core requ1res 250 AT form agnet1zat1on, the percentage rat1o error 1s (a) 10.56 (b) -10.56 (c) 11.80 r)~

The val tage flux adj ustm en t of a certain 1-ph ase 22 0 V i~n watt hour meter 1s altered so that the phase angle between the:fj ~tage and the flux due to 1t 1s 85 (Instead of 90). The errors mtro the read1ng of th1s meter when the current 1 s sA at power fact au - and o. s 1 agg mg are resp ect1vel y. (a) 3.8 mW, 77.4 mW ~ w, -77.4 mW (c) -4.2 w, -85.1 W 4 "'U~ W, 85.1 W Group II represnts the figures obt ne~ CRO screen when the voltage s1gnals V" = V m sin oot and Vy = n( ) are given to its X and Y pi ates respectively and is change the correct value of from Group I to match with the corresp on of Group II Group I Group II p =O Q = 1t/2 R 1t

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85. In the circuit shown in Fig. Q8 5, the current gain (~) of the ideal tr ansi star is 10.

86.

The operating point of the tran si star (V co I c) is 10n

~O.SA 15V _l_

(a) (40V, 4A) (b) (40V, SA)

Vdc

Fig.C

(a) Fig. A (b) Fig. B

40V

Vdc Fig.B

Fig.D

(c) Fig. C

own in Fig.Q86. The

(d) Fig. D

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87. A chopper is employed to charge a battery as shown in Fig. Q8 7. The charging current is SA. The duty ratio is 0 .2. The chopper output voltage is also shown in Fig. Q8 7. The peak to peak rip pie current in the charging current is

88.

90.

SA\

Clopper

(a) 0.48 A

1.10 v (c) 0.90 v (d) 1.27 v

Vdc

L=20mH

:t (b) 1.2 A

vdctrov n ~ t ~zoo~s

lmS CJ the rm s

o r run with the inverter output frequency set at 40 Hz, and with half lip. The running speed of them otor is

11-00 rpm (b) 22 80 rpm (c) 2 340 rpm (d) 27 90 rpm