Candiilotes slwuJd attempt questions 1 and 5 which arecompulsory andanythree oftheremaining
questions selection oJ least one question selecting at leastone question/rom e(f£h Section.

SECIIONA
Answer any three of the following
State and explain Thevein's theorem and replace the active network of the figure given below, allermmal s ab with a Thevenin' s eqUivalent <img src='./qimages/1132-1a1.jpg'>
Determine the currents i1,i2 and i4 at t=0 for the Circuit given below Assume that the voltage source is applied at t =-infinity <img src='./qimages/1132-1a2.jpg'>
Determine inverse Laplace transfonn of <img src='./qimages/1132-1b1.jpg'>
Given E=xe0e-jk in a regiOn, where k is a constant Find the time average Poynting vector
Silicon diodes D1and D2 in the Circuit of the figure given below have saturation current of 1 nA and 20 nA, respectively, at 300 K. Find i1,i2,v1,v2 Given Boltzmann constant 1.38 x 10.23 electronic charge q 1.6 x 10.19 C and emission coefficlent n 1 forGe and2for Si <img src='./qimages/1132-1b3.jpg'>
DeSign a 2-input, 3-output a circuit which can be used as half adder or half subtractor by choosing output p oints
Derive an expressiOn for armature torque of a dc motor m terms of back emf armature current and sp eed in rpm
What will be the value of cos ¢ at zero voltage regulation for a smgle phase transfonner?

Two random van abIes X and Y have the Jomt <img src='./qimages/1132-1d1.jpg'> Where A is a constant Evaluate A and detenrune the margmal p dfs and draw the corresp onding graphs
At great distances from the Hertzian dipole antenna the EM fields resemble those of a uniform plane wave. Write the Similarities and differences (at least five pomts)

2. define a network function and explam how the poles zeros are related to a network function

Explain how an analog Signal can be constructed from its samples. What are the conditions for faithful reconstruction? Give anyone reconstruction arcuit
An airline has charactenstic lmpedance of75 ohms and phase constant of3 rad/m at 100 MHz, Find the lnductance and capacitance per meter of the line
(iv)Input voltage to the Circuit of the figure giVen belowlS Vm= 12 sm t V Detemune the output voltage Va and sketch!1, What iS the name 0 f the Circuit?
Determine input se resp onse of the system des cribed by difference equation
<img src='./qimages/1132-2a4.jpg'>
b.(i)Draw the phaser diagram of a Single-phase transfonner For a smgle-phase transformer of 440/4400 volts, 50 Hz, the no load current iS 0 04 amps. Transfonner mput-power fed from low voltage Side lS 80 watts Calculate iron loss and magnetizmg component of currents and the power factor at no load
A 1500 kVA, 6.6/1.1kV, 3-0 delta-star connected transformer has the following test data, when low voltage Side iS short-Circuited 300V,30kW,1312A Calculate
reSiStance and reactance drop s
regulation on fulll0ad and 0.8 P.F.lag
A battery is charged by a smgle-phase half-wave controlled rectifier usmg SCR circuit. A reSlslance of 10 ohms iS used between rectifier and ballery. An ac source voltage 0 f 23 0 50 Hz iS used as mputto rectifier If the battery voltage iS 150 V de, ficd
average chargmg current
power supplied to battery
How iS an SCR protected against high dt/dt and dv/dt? Give Circuit configuration and
explain the role of each component
For the circuit given below draw the network graph and draw any three possible trees
ofthe network
Prove that for the network graph L B where
L=no of links
B no of branches
N=no of nodes
<img src='./qimages/1132-3a1.jpg'>
determine impulse response of the system described by difference
equation

The Ideal op-amp circuit of the figure given below converts voltage Vi mto a current Show that If 2R, 2R, R3+ and then'L=+VimA
<img src='./qimages/1132-3a3.jpg'>
Explain hunting phenomena in a synchronous motor operating at constant voltage and
field eXCitation, when load on the shaftlS suddenly decreased
For aleading power factor load, draw phaser diagram of a synchronous motor
A motor is rated as follows
400 star connected, R. 0.2 ohm, Xs= 2 ohm For 20 A armature current calculate excitation emf at 0 8 leading P. F condition
Draw the Circuit diagram 0f a step-up/step-down dc chopper Write expreSSiOn for the average output voltage uSing energy bal ance equation
A chopper Circuit iS operating on Time Ratio Control strategy at a frequency 0f 2 kHz on 220 V dc supply. If the load voltage iS 200 V dc, compute the conduction and blocking penod of SCR ineach cycle
Compute the quality factor of an RLC senes Circuit With R 20, omega, 50mM and
C=l mew using
<img src='./qimages/1132-4a.jpg'>
Impulse response and input to a discrete time system are given as


Determine response of the system.5
List is ascending order the frequencies of the five lowest (frequency) modes of an air-filled rectangul ar cavity of dimenSions
5 x 4 x 2.5cm
Describe what happens to each of the following CMOS charactenstics as VDD is increased
NOiSe margin
(ii)Power disSipation
(iii)Switching speed

Show that the Signal sigma[cos wt cos (wit+02)-sin omegac tsin is an SSB
Signal. is it USB or LSB? Write an expression for the missing Sideband Obtaln an expreSSiOn for the total DSB-SC Signal
A white-noise current source having a power spectral density n/2 is filtered by a narrow b and, parallel single-tuned Circuit having a resonant frequency at f0 and a 3­dBb and width B «f0. Find the output voltage noise power
The ionosphere can be conSidered as a dielectric with refractive index n. Denve an expressiOn forn
SECTION B
Answer any three of the folloWlng
A balanced three-phase system has a lme voltage of 500 V Two balanced Y­connected loads are present One is a capacitive load with per phase, and the other is an mductive load with 0 per phase. Find the phase voltage; the line current, the total power drawn by the load; the power factor at which source is operating Draw the CircUlt arrangement also
Find the voltage transfer function V,I for the network given below motor
<img src='./qimages/1132-5a2.jpg'>
Impulse response of two systems are gJ ven as
u[n
Determine which 0f the above systems are causal, memory less
A lossless parallel strip line has a conducting Width W. The substrate dielectric
constant iS 10 and has a thickness of4 mn. Calculate the value of W to have a
characterinstic impedance of75 omega and also the line capacitance
What is the impedance reflection pnrinciple as referred to FET Circuits? Draw the circuit of a typiCal source follower and apply reflection principle to obtain its output eqUivalent Circuit
Determine
maximum conversion rate
average conversion rate
maximum conversion time
for a I6-bit counter typ e A/D converter using a I MHz clock
Explain the speed-current, torque-current and speed-torque charactenstics of dc senes
In case of three-phase induction motor, load torque as
.<img src='./qimages/1132-5c2.jpg'>
derive the ratio of maximum torque to full
A fully controlled three-phase bridge iS operating in inverting mode from an ac supply of 220 50 Hz. The source inductance per phase lS 0.32 mH. If the converter iS operating with an angle of finng advance of calculate maXimum current that can be commuted, allowing a recovery angle of 5° Neglect device volt drops in an Armstrong modulator the crystal frequency iS 200 kHz The angular deVlation iS to be 0.2 and the system iS to accommodate modulation frequenCies down to 40 Hz
At the o/P the carrier frequency iS to be 108 MHz and the frequency deviation be 80 kHz. Detenmne multipli er and nuxer oscillator frequencies to accomplish this end
A magnetic field strength of 15 mew a/m is reqUired at a point on x 2 km from an antenna In alL Neglect ohmicloss How much power would the antenna transmit If it is
a lamda/2 dipole?
a 10 turn 100 P antenna of radius lamda/20?

for the giVen network shown below driven by a current source and terminated by a
<img src='./qimages/1132-6a1.jpg'>
resiStor R2 at port calculate the transfer functions y21(s) and the driving point functions
Prove that If at t 0 there iS a charge density p in Side a conductor, then c/o seconds
later the density will decrease to [1/e]p.For copper (sigma= 5 x 107 calculate this
time
minimize and implement the following multiple-output functions
sigma(1, 12, 14, 15)
sigma(1, 12, 13)
In a DSB-SC system, the carrier frequency iS £o= 500 kHz and the modulating Signal met has a urufonn PSD band-l1nuted to 4 kHz The modulated SignalS transmitted over a distortion less channel with a noise PSD
<img src='./qimages/1132-6b.jpg'>
The useful Signal power at the receiver input iS 1meww The received Signal iS band pass filtered, multiplied by 2 cosomegact and then low pass filtered to obtam the output Determine the output SNR
Draw a neat schematic of a traveling-wave amplifier List the elements of the tube and theirb constructional details
Campare the salient features of 0-and M-type tubes. (at least eight pOints)
7. Find the current I in the Circuit shown below
<img src='./qimages/1132-7a1.jpg'>
Determine the time Signal represented by the DTFS coefficients given in the figure below
<img src='./qimages/1132-7a2.jpg'>
A plane wave is normally inCident on a half-space of copper Iff= 2 GHz, calculate
propagation constant, impedance and skin depth forthe conductor
reflection and transmission coefficients
Given sigma=5.8x lO7S/m.
For the Circuit of the figure given below beta= 100, R1= 90 komega, R2=10komega, Rc=5komega
RE=lkomega andVcc =20V
Determine ib,ic and VCE
<img src='./qimages/1132-7a4.jpg'>
Find the mean, the mean square, and the vanance of the GausSian random vanable with the ,dE
<img src='./qimages/1132-7b.jpg'>
Draw a Simple two -valley conduction b and diagram for GaAs The band structure 0f a semiconductor must satisfy three criterions to exhibit negative reSiStance for transferred electron effect 10 occur. State them
With the help of neat sketches explain the fabrication steps for making MOSFETs.
8.a.(i)Define the followinng terms related to electrical circuits
An ideal filter
SPICE
Network graph d
Prove that -zd/zd
where
without any change in ROC
What do you understand by Miller capacitance? For a CE amplifier following parameters are given
<img src='./qimages/1132-8a3.jpg'>
Determine the Mill capacitance

Draw the logic diagram and timing diagram 0f a 3-bit binary ripple up counter using positive edge triggered FF's

A 400 V de shunt molor has no -10 ad sp eed 0f 2000rpm It is runninng at I 00 0 rpm at £Ull10ad torque, reduced armature voltage and full field. Its load torque is reduced to 50% 0f rated value with armature voltage and field voltage held constant at preVIous
values; the speed 1ncreases to 1050 rpm Find armature voltage drop at £Ull10ad Neglect effect of armature reaction
A 500 3-phase star connected synchronous motor has a reSiStance and synchronous reactance of 0.4 ohms and 3.6 ohms per phase respectively The open circuit voltage is 600 V If friction and core loss are I kW calculate line current and power factor when motor OUtpUtlS 62 kW
Explain brifly the different control strategies of chopper
An ideal Single quadrant chopper operating in first quadrant iS supplied with power from an ideal battery source oftenmnal voltage 200 V The load voltage waveform conSists of rectangular pulses of duration I msec m overall chopper time of 3 msec Calculate the average and nns values of the load voltage and voltage npple factor
A 200 875 rpm, 150 separately excited de motor has an armature reSiStance of
0.060. it iS fed from a single phase fully controlled rectifier with an ac source voltage of no 50 Hz. Assummg continuous conduction, calculate
finng angle for rated motor torque and 750 rpm

motor sp eed for a 160degree and rated torque