A single phase transformer is connected to a supply of voltage V and frequency f and is supplying a

load, connected across its secondary winding. If the supply voltage is reduced from V to V/2, the flux

established in the core will

decrease by nearly 50%

increase by nearly 50%

remain unchanged

be affected by amount of load and not by the applied voltage

Under magnetic saturation of the core of a transformer, the reactance parameters of its equivalent

circuit are affected such that

X1 and X2 increase while Xm does not change

X1 and X2 do not change while Xm decreases

X1 and X2 do not change while Xm increases

X1 and X2 decreases while Xm does not change

A single phase 2000/200 V, 10 kVA, two winding transformer is reconnected as a step-up

autotransformer with 2000 V winding as primary. The kVA rating of the autotransformer shall be

10 kVA

11 kVA

110 kVA

220 kVA

The power factor at which power is drawn by a transformer is

very low under O.C. test but high under S.C. test

high under O.C. test but low under S.C. test

low both under O.C. and S.C. tests

high both under O.C. and S.C. tests

The O.C.C. of a shunt d.c. generator is represented by E = 12+66I. If the field resistance is 70 ohms, the

no-load voltage of the generator will be

144 V

210 V

220 V

288 V

In d.c. shunt motors, the developed torque is proportional to

induced e.m.f.

armature current

output power

line current

The speed of a separately excited d.c. motor can be controlled below base speed by (a) armature

resistance control and (b) supply voltage control. What happens to the slope of modified speed-torque

characteristics under the two methods?

It changes in both types of control

It remains unchanged in both types of control

It remains unchanged in armature resistance control while changes in supply voltage control

It remains unchanged in supply voltage control while changes in armature resistance control

The polarity of interpoles used in d.c. machines is

same as the main pole ahead in generators while opposite of the main pole ahead in motors

same as the main pole ahead ion motors while opposite of the main pole ahead in generators

same as the main pole ahead in both motors and generators

opposite of the main pole ahead in both motors and generators

In synchronous generators, examine the following statements about voltage regulation:

Synchronous impedance method gives pessimistic results

MMF method gives optimistic results

In unsaturated machine both methods (synchronous impedance and MMF) give same result

Which of the statements are correct?

1, 2 and 3

Only 1 and 2

Only 3

Only 2 and 3

Under symmetrical short circuit of a synchronous generator, the armature reaction is

magnetizing

demagnetizing

cross-magnetising

mainly magnetising

In synchronous generators, the fifth harmonic in induced emf can be eliminated by using coils show

chorded by an angle

9o

18o

27 o

36o

In induction motor operation, a slip greater than 1 refers to

regenerative braking

motoring in reverse direction

plugging

dynamic braking

As the applied voltage to an induction motor, operating under no-load, is reduced to half

its speed reduced and stator current increases

its speed reduced and stator current also reduces

its speed reduces but there is not change in stator current

there is no change in speed but stator current reduces

A 3-phase induction motor is delivering a load of 10 kW at a lagging p.f. of 0.5. If a 3-phase capacitor

bank of 7.3 kVAR is connected at its input, the resulting kVA drawn from supply shall be (approximately)

26.5

24.5

20.0

14.0

An electric motor developing a starting torque of 10 Nm starts with a load of 6 Nm at its shaft. If the

acceleration at start is 2 rad/sec2 , the moment of inertia of the system must be

2 kg-m2

2 N-m2

0.5 kg-m2

0.5 N-m2

A synchronous motor works as a synchronous condenser if

underexcited

overexcited

excited with 100% excitation

unexcited

In relation to damper bar winding in a synchronous motor, examine the following statements:

Damper bars are provided in slots on poles

Damper bars improve excitation

Damper bars help the motor self start

Damper bars minimize hunting.

Which of the statements are correct?

1, 2, 3

2, 3

1, 4

1, 3, 4

In large power ratings, synchronous motor is considered superior to induction motor, since

it is less expensive

its efficiency is better

it can be operated at better power factor

its speed regulation is superior.

An induction motor drive is designed for two speed operation. For this purpose, the motor is provided

with two windings on its stator corresponding to 4 poles and 8 poles. While the motor was running on 4

pole winding, a changeover to 8 pole winding is made. The motor will

experience dynamic braking

experience regenerative braking

experience no braking but will slow down due to its inertia

draw dangerously high current

A d.c. shunt motor drive of 100 h.p. is run (a) at half the rated speed by armature voltage control and

(b) at 1.5 times the rated speed by field control. Its power rating in the two cases shall be modified as

100 h.p. in both cases

50 h.p. in case (a) and 150 h.p. in case (b)

50 h.p. in case (a) and 100 h.p. in case (b)

100 h.p. in case (a) and 150 h.p. in case (b)

A single phase full controlled rectifier can work as inverter, if the firing angle is between

0o and 90o

60o and 90o

90o and 180o

0o and 60o

When d.c. voltage is converted to a.c. by an inverter, PWM technique is used to

control only the output voltage from within the inverter

control both the output voltage and frequency from within the inverter

control the output current

reduce losses in the inverter

A thyristor which is in ON state is to be switched OFF. For this purpose a reverse bias is applied across

it. Examine the following statements regarding flow of current from anode to cathode (forward current):

Forward current can continue to flow if the circuit is purely resistive

Forward current can continue to flow if the circuit is dominantly inductive

Forward current can continue to flow if the circuit is dominantly capacitive

Forward current will immediately stop flowing.

Which of the above statements are correct?

Only 4

Only 1

Only 2 and 3

Only 2

In a 3-phase full controlled thyristor bridge rectifier operating under continuous conduction mode,

each thyristor conducts for

180o and two thyristors conduct at a time

120o and three thyristors conduct at a time

180o and three thyristors conduct at a time

120o and two thyristors conduct at a time

A single phase fully controlled rectifier is feeding a d.c. motor. At a = 0o, the armature voltage is 200 V

and motor speed is 1000 rpm. Neglecting armature resistance and considering continuous conduction,

the armature voltage and speed at a = 60o will be

100 V and 500 rpm

100 V and 1000 rpm

200 V and 500 rpm

100 V and speed will depend upon load

The grading capacitors are provided across the series connected interrupters in EHV circuit breakers

for

reducing short circuit current

improving power factor

equalizing distribution of recovery voltage across the interrupters

preventing inductive current chopping.

The minimum cost operating condition for a thermal plant is that

the larger units should generate more power as compared to smaller units

the smaller units should generate more power as compared to larger units

the incremental cost rate of the units be proportional to their rating

the incremental cost rate of all the units be equal

The effect of earth on a three-phase transmission line is to

increase its capacitance and decrease inductance

decrease its capacitance and increase inductance

increase its capacitance without affecting inductance

increase its inductance without affecting capacitance.

In case of a transmission line if the voltage regulation is negative, then the load power factor is

zero

lagging

unity

leading

The voltage gradient at the surface of a cable, having a conductor of radius r and a sheath of radius R,

is minimum when

R = r/e

R = r

R =er

R = er

where e = natural exponent

In an N-bus power system with M-PV buses, the size of the Jacobian matrix for load flow calculation is

N×N

(N-M) ×(N-M)

(N-1) × (N-1)

(N-M-1) × (N-M-1)

The zero-sequence equivalent circuit of a delta-star transformer, with solidly grounded neutral, is

The plug setting multiplier of a 5 Amp. IDMT relay for a fault current of 4000 Amp. and a relay setting

of 125%, with a C.T. ratio of 80 will be

1

2

4

8

If the cost of electricity generation is to be reduced then

the diversity factor and load factor both should be low

the diversity factor and load factor both should be high

the diversity factor should be high while the load factor should be low

the diversity factor should be low and the load factor should be high

The coefficients of reflection for voltage and current for an open ended line are respectively

-1.0 and -1.0

-1.0 and 1.0

1.0 and 1.0

1.0 and -1.0

If G is the MVA rating of a synchronous machine with inertia constant H sec. and operating frequency

f, then the angular momentum M of the machine, in MJ-sec/electrical degree, is

Circular grooves are provided underneath the insulator disc for

reducing the weight of the disc

improving disc strength

increasing cooling of the disc

increasing the creepage distance

The arc formation in vacuum circuit breaker is initiated by

field emission

thermal emission

photo emission

secondary emission

The series reactors are used to

limit over voltages

control Ferranti effect

limit fault current

improve stability

If the spacings Dab, Dbc and Dca between the phases a, b, and c of a three phase transmission line are

not equal, then the equivalent spacing Deq can be calculated as

(Dab + Dbc + Dca)/3

(Dab * Dbc * Dca)/3

(Dab + Dbc + Dca)1/3

(Dab * Dbc * Dca)1/3

For calculating fault current for a double line to ground fault in an ungrounded system

positive, negative and zero sequence networks are connected in series

positive, negative and zero sequence networks are connected in parallel

positive and negative sequence networks are connected in parallel

positive and negative sequence networks are connected in series

The unit of R, the regulation constant of turbine speed governor, is

Hz/MW

MW/sec

MW/Hz

MW-Hz

If in a power system the line to line base voltage is VB kV and the 3-phase base MVA is SB, then the

base impedance of the system is

The pumped storage hydro plants are used as

Base load plants

Peak load plants

Mid-range plants

both (A) and (B)

The specified operating criteria for the proper operation of interconnected power system is , that Area

Control Error (ACE) must be zero at least once in a

1 sec period

1 min period

10 min period

1 hr period

If a network has b branches and n nodes, then the number of independent KVL equations for the

network are

b-n

n-b+1

b-n-1

b-n+1

What will be the value of ZL for maximum power transfer condition in the circuit shown in Fig. Q.47?

(2-j2)W

(2+j2)W

(3-j2)W

(3+j2)W

Which of the following statements does not apply to series RLC circuit?

The current and the admittance are maximum at resonance

The phase angle of the impedance changes from +90o to –90o as the frequency is varied from 0 to ¥

The total stored energy in the circuit is constant at resonance

The power factor is unity at resonance

The average value of a sine wave over a full cycle is

zero

A two port network is reciprocal and symmetrical, if ABCD parameters satisfy the conditions:

AB-CD = 1 and A = D

AD-BC = 1 and A = D

AC-BD = 1 and A = D

AD-BC = 1 and B = C

Tellegen’s theorem is applicable to

linear time invariant networks only

non-linear time invariant network only

any network satisfying Kirchoff’s current and voltage laws

linear time variant network only

The circuit element having identical properties for forward and reverse direction of current flow

through it, is called a

linear element

irreversible element

bilateral element

unilateral element

A fundamental cut set contains

only one tree branch and minimum number of links

only one link and minimum number of tree branches

only tree branches

only links

In the circuit shown in Fig. Q. 54 if the switch is opened at t = 0 and the initial current through the

switch and L1 is 10 A, then the current i(t) and the voltage v(t) of t > 0 are

0 A, 0 V

0 A, ¥ V

6 A, 12 V

10 A, 20 V

The Thevenin and Norton equivalents of network A at points X, Y (Fig. Q.55) can not be found if

Networks A and B are coupled

A is an active network

B is a passive network

B is a non-linear network

If X×Y= 0 then XÅY is equal to

X+Y

1

The value of base x will be

(101)x + (110)7 = (101)8 + (29)16

2

7

8

10

Consider the counter circuit shown in Fig. Q.58.

If the present state QA QB of the counter is QA = 1 & QB = 0, the next state of the counter will be

QA = 1, QB = 1

QA = 1, QB = 0

QA = 0, QB = 1

QA = 0, QB = 0

In 8085 A mp, stack pointer is a 16 bit register which is

Incremented by 2 whenever data is pushed on to stack

Incremented by 2 whenever data is popped from stack

Incremented by 1 whenever data is pushed on the stack

Neither incremented nor decremented a result of PUSH and POP operation

The instruction LDA 0805H is used to input a data from an I/O device. Choose the correct statement

It is possible only if device is interfaced using memory mapped I/O

It is possible only if device is interfaced using I/O mapped I/O

Instead of LDA 0805H, the instruction STA 0805H should be used

only IN PORT instruction can be used in 8085 A mp.

The macro RTL implemented by INR M in 8085 A microprocessor is

(M)¬ (M) +1

(H,L)¬(H,L) + 1

M(H,L) ¬M(H,L) +1

(H) ¬ (H) + 1, (L) ¬ (L) +1

In an 8085 A microprocessor when INTR interrupt, becomes active, the control will be transferred to

0024 H memory location

003C H memory location

anywhere in the memory decided by the interrupting device

0034 H memory location

In an 8255 programmable peripheral interface both the groups are programmed in made ‘0’. The

possible number of combination in which the ports can be programmed is

16

4

3

2

The meaning of direct addressing mode is

The address of operand is available in register pair

The address of operand is available in PC

The data is directly available in the instruction itself

The address of the operand is available in the instruction itself.

The schematic symbol shown in following Fig. Q. 65 is that of

Zener diode

Esaki diode

Varistor

Varactor

The V-I characteristic shown in Fig. Q. 66 is that of

PN junction diode

Tunnel diode

Zener diode

Varactor

In a four variable V-K Map shown in Fig. simplified expression for X is

In following circuit assuming voltage drop of LED as 2 V, the LED current when transistor is saturated

will be

12 mA

9.7 mA

6 mA

5.8 mA

In the following circuit the collector voltage VC is (assume VBE = 0.7 V)

-17.4 V

5.6 V

12.3 V

17.4 V

From the following V-K map the simplified expression for Z is

The method of absolute measurement of resistance is

Ohm method

Potentiometer method

Lorenz method

Rayleigh method

The instrument which gives the value of the quantity to be measured in terms of instrument constants

and its deflection is called the

absolute instrument

secondary instrument

recording instrument

integrating instrument

The current passing through a resistor of (50±0.2)W is (4.0±0.02)A. The limiting error in the computed

value of power will be

0.2 %

0.4 %

0.9 %

1.4 %

The coil of an instrument has 40 turns. The mean length of the coil is 25 mm and the axial length of

the coil is 20 mm. If the flux density is 0.1 T and the coil current is 20 mA, the torque on the moving coil

will be

40×10–6 N-m

20×10–6 N-m

40×10–3 N-m

20×10–3 N-m

In thermocouple element, heat energy transferred to the hot junction is converted to electrical energy

by

Johnson’s effect

Seebeck effect

Hall effect

Faraday’s effect

The scale of dynamometer type instrument marked in terms of RMS value would be

uniform throughout

non-uniform, crowded near full scale

non-uniform, crowded at the beginning

non-uniform, crowded around mid-scale

The harmonic distortion percentage is accurately measure with

V.T.V.M.

An oscilloscope

Harmonic distortion meter

Square wave generator

A thermometer has a time constant of 3.5 s. It is quickly taken from a temperature 0oC to water bath

at 100oC. What temperature will be indicated after 1.5 s?

100oC

50oC

35oC

15oC

A digital voltmeter employees an ADC which requires a start pulse, uses an analog comparator and

has a relatively fixed conversion time independent of applied voltage. The ADC is

digital ramp converter

dual slope converter

successive approximation converter

flash type

In measurements made using Q-meter, impedance elements should be connected in

star

delta

series

parallel

The measured values of iron losses of a magnetic specimen are 15 W and 25 W at, 40 Hz and 60 Hz

respectively at constant flux density. The respective hysteresis and eddy current losses at 50 Hz are

14.584 W and 5.208 W

7.5 W and 12.5 W

5.208 W and 14.548 W

5 W and 10 W

The most common and best bridge method for precise measurement of inductance over a wise range

is

Maxwell’s

Hay’s

Wien

Anderson

The AC bridge that can be used for accurate determination of excitation frequency is

Wien bridge

Schering bridge

Anderson bridge

De Sauty bridge

A thermo-couple arrangement is to be used to measure temperature in the range of 700-800oC. Point

out the pair that would be most suitable for this application

Copper-constantan

Chromel-alumel

Platinum-platinum rhodium

Iron-constantan

Rotameter is employed for measuring

flow

rotation

specific gravity

viscosity

Consider the following statements regarding the stability of a control system

Gain margin and phase margin are negative

Gain margin and phase margin are positive

All roots of characteristic equation must lie in left half of s-plane

Gain margin is positive and phase margin is negative

Out of these statements

1 and 3 are correct

1 and 2 correct

2 and 3 are correct

3 and 4 are correct

In the feedback system shown below, if the steady state error for a step input is 0.05, then the value

of K is

0.05

0.95

1.9

19

Match List I with List II and select the correct answer using the codes given below the lists:

List I (Location of poles on s-plane)

List II (Impulse Response)

Codes:

A B C D

4 1 2 3

3 4 2 1

1 3 2 4

1 3 4 2

The Nyquist plot for a control system is shown in Fig. Q.89. The Bode plot of |G| for the same system

will be

A unity feedback second order control system is characterized by

where

J = moment of inertia

B = viscous damping coefficient

K = system gain

The transient response specification which is not affected by variation of system gain is the

peak overshoot

damped frequency of oscillations

setting time

rise time

The second order system X = AX has . The value of its damping factor x and natural frequency wn are

respectively

0.5 and 1

1 and 1

0.707 and 2

1 and 2

A negative unit feedback system has forward path transfer function as Ks/(s2+2s+25). The break in

point(s) of root locus occur at

s=5

s=-5

both A & B

s = 25

In an electrical analog of mechanical system of rotational motion, using torque-voltage analogy,

inertial and viscous damper are respectively analogous to

Inductance and capacitance

Capacitance and resistance

Inductance and resistance

Capacitance and inductance

The characteristic equation of a feedback system is given by

For this system, stable closed loop behavior can be ensured when gain K is such that

0 £ K £ 40

0 £ K £ 10

0 £ K £ ¥

0 £ K £ 20

The eigen values of the matrix are

(a+1), 0

a, 0

(a-1), (a-1)

0, 0

A first order linear system is initially relaxed. For a unit step signal u(t), the response of the system is

(1-e-3t), t > 0

If a signal 3. u(t) + d(t) is applied to the same initially relaxed system, the response will be

3(1-e-3t) .u(t)+ e-3t. d(t)

(1-3e-3t) .u(t)

3(1+e-3t) .u(t)

3.u(t)

Consider the following statements regarding the non linear system

dead zone can be classified as single valued non-linearity

hysteresis and backlash can be classified as double valued non-linearity

Coulomb friction can be classified as double valued non-linearity

Out of these statements

1 and 3 are correct

all three are correct

1 and 2 are correct

2 and 3 are correct

Consider the system

.

The condition for complete state controllability and complete observability is

d1 > 0, b2 > 0, b1 and d2 can be anything

d1 > 0, d2 > 0, b1 and b2 can be anything

b1 > 0, b2 > 0, d1 and d2 can be anything

b1 > 0, b2 > 0, d1 < 0 and d2 can be anything

The semilog plot of gain characteristic (BODE plot) of a network is shown in the Fig. Q.99.

The gain cross over frequency wc is

20 rad/sec

30 rad/sec

40 rad/sec

25 rad/sec

The pole-zero configuration of a phase lead compensating network is given by