K-Test - 23

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Technical

a. 4 mW b. 0.1 W c. 1 mW d. 0.4 W

1. Consider the circuit given below. Maximum power that can be transferred to RL is

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K-TEST 2016

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a. e b. c. d. a. LPF b. HPF c. BPF d. BSF

CORRECT YOUR ANS. B CORRECT ANS. B

2.

__________

CORRECT YOUR ANS. C CORRECT ANS. C

3.

The transfer function of the system represents

  We have

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a. 6 states b. 12 states c. 32 states d. 2n states a. Under OCC, the air gap flux is in opposite direction to the normal armature. b. Under short circuit test, there is high flux density and rated short circuit current. c. The power factor under short circuit condition is ZPF lead. d. Armature reaction under short circuit condition is purely demagnetization. a. b. infinity

INCORRECT YOUR ANS. C CORRECT ANS. D

4. A Ring counter consisting of six flip-flops will have

CORRECT YOUR ANS. A CORRECT ANS. A

5. Determine the TRUE statement from the following regarding alternators.

CORRECT YOUR ANS. D CORRECT ANS. D

6.

The impedance at the middle of a lossless transmission line (characteristic impedance Z0) of length and whose both ends are open is given by

  n-bit ring counter is a MOD-n counter. So a 6-bit ring counter has 6 states.  In the short circuit test, entire emf Ef is consumed in circulating the short circuit current Isc, through the synchronous impedance Zs , Therefore, Ff (field mmf) and Fa (armature mmf) are out of phase and due to this saturation doesn’t occur and the characteristic is linear .

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d. zero a. 56 µA b. 140 µA c. 60 µA d. 3 µA NOT ATTEMPTED CORRECT ANS. D

7.

_If _{, then div at (1,-1,0) is} ____.

CORRECT YOUR ANS. 0 CORRECT ANS. 0

8.

In the figure given below, assuming and , the minimum base current required to drive the transistor to saturation is



Take the ratio of sending end voltage and current to derive input impedance for loss less line ( )

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a. Allow a low impedance path to the high frequency component of DC link current b. Minimize high frequency current ripple through the ideal DC source

c. Maintain a constant DC link current d. Protect against switch failure

9. A large capacitor set across DC bus of a voltage source inverter, intended to

10.

In the complex plane, the angle between origin and line , origin and is _________ degree. (where, )

11.

 Minimum base current  then it acts as low pass filter.  _Let Then Angle between and

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a. -j 19.8 p.u b. +j 20.0 p.u. c. +j 0.2 p.u. d. –j 19.95 p.u. a. In the potential coil connected across the load b. In the potential coil connected across the supply c. Both (a) & (b) d. Not required in Dynamo meter type a. 70%, 17.32 b. 100%, 2 c. 20%, undefined

The network shown in the given figure has impedances in p.u. as indicated. The diagonal element of the bus admittance matrix of the network is

12. In dynamo meter type watt meter, the compensating winding is required

INCORRECT YOUR ANS. C CORRECT ANS. A

13.

Peak overshoot and peak time for a second order unity feedback system are





To overcome error due to inductance in voltage coil, compensating winding is used in the potential coil.

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d. No peak exists, undefined a. Open-circuit voltage to the short-circuit current at a given excitation b. Short circuit voltage to the open-circuit voltage at a given excitation c. Excitation current required for the rated voltage on open-circuit to the excitation current required for the rated armature current under short-circuit d. Excitation current required for the rated armature current under short-circuit to the excitation current required for rated voltage on open-circuit

14.

Vx in the circuit is ______________ V.

CORRECT YOUR ANS. 4.167 CORRECT ANS. 3.6, 4.8

15. Short circuit ratio of a synchronous machine is the ratio of the

INCORRECT YOUR ANS. D CORRECT ANS. C

16.

Given ; . If is a singular matrix and then the value of a is ___________.  The system is overdamped.  Applying KVL, −15 + (1 + 5 + 2)I + 2Vx = 0 But Vx = 5I −15 + 8I + 10I = 0, I = 5/6 Vx = 5I = 25/6 = 4.167V 

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a. b. c. d. a. -4.33 pu b. 2.5 pu c. -0.25 pu d. 1.30 pu

17.

Let x(t) be a real and even signal whose Fourier transform is represented by X(jω). Then which of the following can be a possible X(jω)

18.

A 25 MVA, 11 kV star connected synchronous generator has its neutral point solidly grounded. The generator is operating at no-load at rated voltage. Its sequence reactance’s are 0.20pu & =0.08pu. The symmetrical sub-transient line current for double line fault is

19.

 _Since _{is singular ? det.} Now, Compare with given equation  If x(t) is real and even its Fourier transform should be real and even thus only option (c) satisfies, because (a) is an odd function while (b) and (d) are imaginary functions. 

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a. b. c. d. a. 1 & 2 b. 2 & 3 c. 1 & 3 d. 1, 2 & 3

The length and breadth of a rectangle is 3m and 4m. What is the area of the rectangle, if there is an error in length and breadth of 2% and 4% measured respectively?

20.

On a generator O.C. and S.C. tests were conducted are result are given in the below: O.C. test S.C. test

If the rating of generator is 100 MVA, its S.C. MVA is ___________________.

INCORRECT YOUR ANS. 25 CORRECT ANS. 400

21.

Consider the following statements regarding IGBT. 1. It can block negative voltages like GTO. 2. It has low ON state power loss like Power BJT.

3. It has high input impedance gate like a Power MOSFET. Which of the above statements are correct?

INCORRECT YOUR ANS. C CORRECT ANS. B  The errors in length and breadth Area of rectangle=   IGBT is a combination of BJT and MOSFET.

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a. (10 V, -10 V) b. (0.7 V, -0.7 V) c. (10.7 V, -10.7 V) d. (10.7 V, 0 V) a. If only residual magnetism of original machine is reversed b. If only the field winding connection of original machine is reversed

22.

A box contains tags marked 1, 2 ………. 100. Two tags are chosen at random without replacement. The probability that the numbers on the tags will be consecutive integers is _______________.

CORRECT YOUR ANS. 0.02 CORRECT ANS. 0.02

23.

The output of the network of figure if the input is a 30 V square wave with and .

24.

A DC shunt generator is developing rated terminal voltage at some speed. In which of the following cases, generator does not builds up voltage?

 Favorable outcomes = Numbers chosen consecutively = 99 _{Total outcomes} Required probability  For Z1 forward biased at 0.7 V Z2 reverse biased zener potential ; vice-versa in negative half cycle

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c. If reversal of direction of rotation as well as residual magnetism d. If only the direction of rotation is reversed

INCORRECT YOUR ANS. CORRECT ANS. B

25.

A series generator is connected in series to a feeder having 0.05 ? resistance to boost the voltage. The induced voltage is given by , and . Find the voltage_______V, boosted by the generator, when delivering 300 A?

26.

The number of poles in right half of s-plane of a system with characteristic equation

27.

 If the field terminals are wrongly connected, the field flux opposes the main field flux, so after same time there is no residual magnetism and thereby no build up of the voltage in generator. The residual magnetism of original machine is changed by changing the direction of rotation (i.e., acting as a motor)   Routh Array Total number of sign changes =2 Hence 2 right half poles.

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a. 18.12% and 1.5 b. 20.24% and 2.22 c. 22.04% and 1.22 d. 30.14% and 4.11 a. b. c. d.

If the converter shown in figure has a purely resistive load of R and the delay angle is .

The rectification efficiency and Form Factor (F.F) respectively are

28.

In the network shown below C1 was charged to 10 V and C2 was uncharged initially.

At t=0 switch was closed. The current I(t) flowing through 1? resistor is

 given ; ; rectification efficiency form factor

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a. 2.6V, 4.8mA b. 2.9V, 4.8mA c. 7.6V, 3.7mA d. 7.4V, 4.8mA

29.

Calculate the output voltage and the Zener diode current in the following circuit.



For , converting the circuit into s-domain

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a.

b.

c.

d.

30.

is equal to

CORRECT YOUR ANS. C CORRECT ANS. C  Let I be the current as shown in figure.  Method by cross check Consider, ∴ ∴ ∴ ∴ Hence, (c) is correct answer and we can check the other choices by the similar argument

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31.

A moving coil instrument at normal temperature has resistance 10? of and current of 45mA, gives a full-scale deflection. If its resistance is raised to 10.2 ? due to temperature change, then the percentage error when a current of 2000A is measured by means of shunt of constant resistance will be _________. ?

CORRECT YOUR ANS. -1.96 CORRECT ANS. -2.5, -1.5

32.

A surge of 15kV magnitude travels along a cable towards its junction with an overhead line. The inductance and capacitance of the cable & line are 0.3mH, 0.4μF & 1.5mH, 0.012μF per km respectively. The voltage rise at the junction due to surge will be _________kV

CORRECT YOUR ANS. 27.84 CORRECT ANS. 27, 28

33.

The impedance parameters and of the two-port network shown in the figure, are

 _{=measured value}  Since the surge is travelling from the cable towards the overhead line therefore voltage reflection at the junction will be positive The natural impedance of the line

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b. c. d.

34.

A 20 MVA, 11 kV, 3-phase, delta-connected synchronous motor has a synchronous impedance of 5 ohm/phase. Windage, friction and iron losses amount to 1200 kW. _______ kV (line) is the value of excitation emf at the unity power factor current drawn by the motor at a shaft load of 15 MW.

INCORRECT YOUR ANS. 7.64 CORRECT ANS. 12.5, 14  Using conversion ?Overall Z-parameters _∴ _∴  The phasor diagram is drawn is drawn in given figure

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a. Observable, controllable b. Un-observable, controllable c. Un-controllable, un-observable d. Observable but not controllable

35.

The following controlling system is

INCORRECT YOUR ANS. C CORRECT ANS. A

36.

If the function is implemented, using only NOT and OR gates, then the minimum number of gates required is __________. Assume only A, B & C inputs available.



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a.

b.

c.

d.

37.

A causal discrete-time LTI system is described by . Where x[n] and y[n] are the input and output of the system respectively. Find the impulse response h[n] of the system

38.

 Number of NOT gates = 3 Number of OR gates = 3 Total number of gates = 6 

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a.

b.

A 4 – pole would – rotor induction motor is used as a frequency changer. The starter is connected to a 50 Hz, 3 – phase supply. The load is connected to the rotor slip rings. The possible speeds at which the rotor supply power to this load at 25 Hz are x rpm and y rpm then the sum of x and y is __________. Assume the rotor impedance to be negligible.

39.

Taking for granted the general solution of is of the form for appropriate constants A and B, the value of y(2), where y is the solution that also satisfies

and , is ___________.

CORRECT YOUR ANS. -12 CORRECT ANS. -12

40.

For the circuit shown below, is

(d)

 ∴ We can get 25 Hz voltage at slip _or where ∴ x+y = 3000  _and, From (i) and (ii), we get _and _∴

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c.

d.

INCORRECT YOUR ANS. D CORRECT ANS. B

41.

In a voltage commulated chopper, voltage input , constant load current , switching frequency is 250 Hz, commulating components and . The exact minimum average output voltage is _______________ V.

 KCL at node, ( Voltage at inverted terminal) KCL at node _Since _; from (1) From (2), Combining (3) and (4), Or

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a. 2rad/sec, 16rad/sec b. 4rad/sec, 4rad/sec c. 2rad/sec, 4rad/sec d. 4rad/sec, 16rad/sec

INCORRECT YOUR ANS. 18.75 CORRECT ANS. 31.50, 32.70

42.

Find the magnitudes of and for the given Bode plot.

 Voltage commutated chopper circuit, Circuit turn-off time, The minimum on period for this chopper is, The minimum average output voltage of the circuit is,  From the Bode plot Similarly

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a.

b.

c.

d.

43.

If A & B are mutually exclusive events & then _________

44.

A single phase load of 200 kVA is delivered at 2500V over a short transmission line having .The power factor at the sending end when the power factor of the load is 0.8 leading will be _________.

CORRECT YOUR ANS. 0.827 CORRECT ANS. 0.80, 0.85

45.

 If A & B are mutually exclusive  Load factor equal to 0.8 leading _Here,

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a. Circle centered at (0,-1) with radius 1 b. x axis

c. y axis

d. Circle centered at (0,1) with radius 1

What should be the value of C in µF such that the input power factor is unity for a frequency 60 Hz of the source?

CORRECT YOUR ANS. 442 CORRECT ANS. 441.8, 442.3

46. The point z=x+iy satisfying the equation |z−i|=1 lies on

47.

A step down chopper, feed from 220 V dc, is connected to RL load with and . Chopping frequency is 1250 Hz and duty cycle is 0.5. The average load current is

 The impedance Z of the given circuit is The power factor will be unity (i.e. the phase angle between the input voltage and current will be zero) only if the reactive part of the impedance is zero i.e. if or, Thus, the required capacitance would be 442.09 µF.  The pointed lie on a circle centered at (0,1) with radius 1

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a. 27.5% b. 37.5% c. 47.5% d. 57.5%

48.

A 220 V shunt motor has an armature resistance of 0.5 ohm and takes a current of 40 on full load. By how much must the main flux be reduced to raise the speed by 50%, if the developed torque is constant.

49.

The transfer function of the system is

 Average output voltage, Average load current,  For a DC machine, or, since, torque is constant ; let Eb1 = 220 – (40*0.5) = 200 (9.4 is rejected as it does not given the necessary increase in speed) ;

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a. b. c. d. a. 1475pF b. 1500 pF c. 1525 pF d. 1550 pF

50.

A capacitor consists of two metal plates each of and spaced 6 mm apart. The space between the metal plates is filled with a glass plate thickness of 4 mm and a layer of paper of 2 mm thickness. The relative permittivity’s of the glass and paper are 8 and 2 respectively.

(Given that )



Converting the block diagram into signal flow graph,

Two forward paths and one Individual loop. ∴

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a. b. c. d.

51.

In a CTS x(t) and y(t) denotes the input and output respectively then which of the following corresponds to a casual system?

52.

The function of the following circuit is

 _, _, _, It is a combination of 2 capacitor in series with different dielectrics  It is casual if the y(t) at any time , depends only on present or past or both present and past values of x(t). So, here is only a casual system.

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a. A 2-bit Up/Down counter b. A 2-bit down counter c. Up Counter only when x = 1 d. Down counter only when x = 0

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53.

 P. S i/p F. F i/ps N.S Q1 Q2 x J1 K1 J2 K2 Q1 Q2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 1 0 1 0 0 0 0 0 0 1 0 1 1 1 1 1 1 1 0 1 0 0 0 0 0 0 1 0 1 0 1 0 0 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1 1 1 1 1

1.

0 For x=1 , it counts 00, 01 , 10, 11 Hence up counter

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If a , 20kVA, transformer operates as an auto transformer, then the kVA rating of the autotransformer will be __________.

54.

If then the value of

. Using Simpson's rule, is __________ (2 decimal places)

55.

A transmission line has a resistance and reactance of 10 ohm and 12 ohm per conductor

respectively. if a three phase voltage of 11 kV is applied to the line, then at zero voltage regulation the power delivered to a balanced load of 0.707 leading pf will be __________ kW.



Solution:

kVA rating of autotransformer is= kVA of 2winding transformer



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Aptitude

a. Farmer: pliers b. scalpel: surgeon c. axe: butcher d. mechanic: scissors a. soothed b. slowed c. barred d. bedevilled

1.

Directions for Question: The question below consists of a pair of related words followed by four pairs of words. Select the pair that best expresses the relation in the original pair:

AWL : COBBLER

2.

China’s recent growth has been so impressive that it seems churlish to question whether it can continue. Yet the country will find it more difficult to grow quickly as it becomes richer, as will India and Brazil. All three big emerging markets need to find ways to avoid the inflation that has ________ developing countries in the past, and to strike a good balance between consumption and investment, foreign and domestic demand.

NOT ATTEMPTED CORRECT ANS. D  For zero voltage regulation, So, Power  An awl is a tool used for punching holes in leather, So it’s a tool used by cobbler. Similarly scalper is a tool used by surgeons to cut skin.  Soothed – to calm, ease Bedeviled – to annoy, bother or cause problems,

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a. in b. towards c. for d. on a. He might go to temple every day in his childhood. b. He goes to temple every day. c. He used to go to temple every day till last year. d. He would go to temple every day in his childhood. a. 8

3.

Choose the most appropriate word from the options given below to complete the following sentence:

The driving test is scheduled ____________ Monday afternoon.

4. Which of the following sentence is grammatically INCORRECT?

5.

Simple interest on a certain sum is 16 over 25 of the sum. If the rate of interest and time are equal, then their value is___________.

6.

A third form of verbalization is exploratory talking. This is talking for talking’s sake, aesthetic talking, or, if you like, play talking. Just as that other form of information-transmission, picture-making, became used as a medium for aesthetic expression, so did talking. The poet paralleled the painter. Which of the following is a valid inference from the given paragraph?

  Might implies future and childhood was in past. Here the time sequence of verb and tenses is incorrect. 

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b. Exploratory talking was more expensive than picture-making. c. Picture-making was used as a medium for information retrieval. d. The poet and the painter work towards disparate goals. a. b. c. d. a. 45

7.

If , then the value of is

8. The cost of 4kg of rice, 5kg of wheat and 2kg of toor dal is Rs.165.

_{The cost of 2kg of rice,, 3kg of}

wheat and 4kg toor dal is Rs.171. If the cost of 1kg of rice and 2kg of toor dal is Rs.72, then what is the cost of 5kg of wheat_____Rs

 As per paragraph, the objectives of both picture-making and exploratory talking were information- transmission. Hence, (a) is incorrect. Picture-making was used as a medium for information-transmission retrieval. Hence (b) is incorrect. Information mention in (c) has not been mentioned in the paragraph. Hence (c) is incorrect. As per paragraph, the objectives of both picture-making and exploratory talking were information-transmission. Hence, the purpose was same. Hence (d) is the correct option.  Similarly,

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a. 41

a. 40 b. 60

9.

Given below is information related to installed capacity and generation of electricity in India for a specific year:

Installed capacity (million kW) Generation (billion kWh)

Public -Hydel 11.8 -HydelPublic 46.5

-Thermal (all) 17.6 -Thermal 61.3 -Nuclear 0.8 -Nuclear 3.0 Captive power plants 3.1 Captive power plants 8.5

The closest integral value of capacity utilization for the entire country in the year under consideration is ______________ %.

[Capacity utilization is the ratio of Electricity generated per hour and installed capacity. Assume that all plants work 365 days a year for 24 hours per day].

INCORRECT YOUR ANS. 40.89 CORRECT ANS. 41

10.

The Average marks of boys in class is 52 and that of girls is 42. The average marks of boys and girls combined is 50. The percentage of boys in the class is

 If R, W and T represent respective prices for 1kg of rice, wheat and toor dal, the given data can be written as: 4R + 5W + 2T = 165 ……….. (i) 2R + 3W + 4T = 171 ……….. (ii) R + 2T = 72 ……….. (iii) (ii) – 2 × (iii) 3W = 171 – 144 = 27 ⇒ W = 9 5W = Rs. 9 × 5 = Rs.45  Total installed capacity=33.3 million kW and total power generated=119.3 billion kWh. Percentage utilization Which gives nearest integer value as 41%

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d. 20

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

Let x and y are number of boys and girls in a class respectively.

and