Time Allowed: Three Hours Maximum Marks: 300
Candidates should attlnlpt Questions 1 and 5 winch are compulsory and three of the remaining questions sdecting at least one question from each Section.
SEcnONA
Answer any three of the folloWlng
Determine the power delivered by 6 A source <img src='./qimages/1142-1a1.jpg'>
For the Circuit shown in the figure determine v0/i5 using nodal analySiS <img src='./qimages/1142-1a2.jpg'>
A partially filled truth table of a sequence generator flip-flops in cascade) is given below Find the sequence generated q0 is LSB and q2 is MSB <img src='./qimages/1142-1b1.jpg'>
A D/A converter has the lowest and the highest values of resiStances 1 kO and 4 kQ respectively. If the bit-length of the converter iS to be mcreased by what would be the number of reSiStors reqUired and their values? Draw the complete arcuit of the new converter
A 250 50 hp, lOOO-rpm d.c. shunt motor drives a load that reqUires a constant torque regardless of the speed of operation. The armature Circuit reSiStance iS 0.04 o. When this motor delivers rated power, the armature current iS 160 A
If the flux iS reduced to 70°/0 of its onginal value, find the new value of the armature current
What is the new speed?(10)
List the sources 0f noise m bip 01 ar tranS! stor(10)
A 100 kc resistor iS connected in parallel with a 100 pE capaator Determine the effective noise bandoWidth and the nOise voltage appearing at the tenrunals of the combination at 27° C
Solve the folloWing difference equation by use of the z transfonn method
1
Obtain the inverse z transform of

For a three-phase induction motor, establish the ratio of maXimum torque to full-load torque in the form.

<img src='./qimages/1142-2b1.jpg'>
An induction motor of squirrel cage type has starting current 5 times of full-load current and full-load slip, of Evaluate maximum torque and corresponding slip and relation of starting torque to full-load torque Assume the stator impedance and magnetiSing current negligible
What is the essential difference in commutation perfonnance of triac and two thynstors connected m antiparalle1
A battery is charged through a reSiStor R as shown <img src='./qimages/1142-2c2.jpg'> If F is 220 V E" 100 V and R 200, calculate the batteJY chargmg current and power supplied to the battery
write the Maxwell's equation in a lossy dielectric and explain that the electric field leads the magnetic field in time phase
Explain the term intrinsic impedance and its value in free space
(iii)From Maxwell's equation stale the Slgll1ficance of the lenn c!OlG What WIll be its value for a good conductor and a good dielectric?

A three-phase 440 60 Hz, star-connected eight-pole, lOO-hp induction molor has the following parameters expressed per phase
r1=O 0.06omegax1=x2'=0.26 omega
048omega, rc=107.5omega
x.=8.47omega s=0.03
The rolational losses are 160 W Using the apprOXimate eqUivalent circuit determine
the input me current and power factor,
the efficiency
What are the advantages of half-controlled converters over fully-controlled converters? Show the output voltage waveforms for controlled and uncontrolled halves of the converter and the resultant voltage

The speed ofa 20-hp, 220 1000 rpm de senes motor iS controlled by asingle phase
half-controlled full wave 1deal converter Senes field wmding and armature winding have resistances 0.05omega and 0.12 0 respectively Input to converter iS 230 50 Hz supply
Calculate the motor torque, current and supply power factor at rated load and speed for finng delay angle a 30° Assume motor current to be continuous and ripple free ReSidual back emf constantlS 0.08 VI radlsec and armature current, dependent back emf (or torque) constant iS 0.04 Nm/A2.

Derive the condition of oscillation and the expression for the frequency of oscillations for the Circuit shown (Use mesh analySiS and Barkhausen's criteria). Draw actual oscillator circuit with one operational amplifier and minimum number of RC elements <img src='./qimages/1142-4a1.jpg'>
The ac eqUivalent circuit of an tranSiStor circuit is shown below Draw the actual circuit with biasing and coupling cap acitors <img src='./qimages/1142-4a2.jpg'>

Show that at 100% modulation index, power contained min one Side band of AM system is 1/6ft. 0f total power transmitted.
A standard AM transmiSSion, sinusoidally modulated to a depth of 30 produces Side frequencies of4.928 and 4.914 MHz. The amplitude of each Side frequency is 75
(iii)Define conditional probability and random variable
Explain tropospheric scatter propagation
A reflex klystron operates at the peak 0f the n 2 mode The dc power input iS 40mW and V1/v0=0.278 If 20% of the power delivered by the beam is diSSipated in the cavity walls, find the power delivered to the load. Assume b1= 1 andj1= (1.53) 0.562
(iii)Define conditional probability and random variable
Explain tropospheric scalier propagation

A reflex klystron op erates at the peak 0f the n 2 mode The dc power input iS 4 OmW and V,No 0.278 If 20% of the power delivered by the beam is diSSipated in the cavity walls, find the power delivered to the load. Assume b1= 1 and j1=(1.53) 0.562
SECTION B
Answer any Three of the following
State and prove the frequency -shift theorem
Determine the Laplace transform of shOw in the figure, using the frequency-shift theorem
<img src='./qimages/1142-5a1.jpg'>
A system has impulse response e-at What would be the response of the system, if it is excited by a delayed unit step function (delay=t)

i. <img src='./qimages/1142-5b1.jpg'> The above circuit is intended for NOT operation for input leves 0 and 10 V. Calculate the minimum value of R for which this operation is possible Assume hFE 30, VBE VCE(sat) 0 .2 1n respect of above silicon tranSiStor
implement an OR gate with AND and NOT gates
Draw a positive logic OR gale with two diodes and explain its operation
Draw and explain the speed, torque and power-time curves for a typiCal electrical traction drive Differentiale c1early between dynamic Cand regenerative braking.(10)
A 3-phase, 400 Six-pole, 50 Hz induction motor with parameters Rs =Rr 1omega Xs 2omega(referred to stator) is under regenerative braking action. Calculate the maXimum overhauling torque that it can hold and the range of speed for safe operation and the speed at which it will hold the overhauling load with torque of 160N-m
List the differences between microwave tranSistors and transferred e1ectron devices

Explain the structure 0f IMPAIT diode
List the properties 0f S-parameters

Use Thevenin's theorem to replace the three-loop circuits of figure by a Single-loop eqUivalent circuit in which the identity of RL is preserved
Find the value of RL so that the maXimum power is consumed in it i. <img src='./qimages/1142-6a2.jpg'>
Explain principle of super-heterodyning List the advantages of super-heterodyne
receiver over TRF receiver
Explain PLL FM demodulator
A certain microstrip line has the following parameters sigmar =5.23, h 8mils 1=28mils,W=10mils Calculate the characteristic inpedance Zo of the line
Compare linear brodside arrays having uniform binominal and Dolph ­Tchebyscheff distributions
Draw the field lines and equipotential surface when a point charge is placed near an infinite grounded conducting plane
Derive the expression for the force between the point charge and the conductor with the help of the above concept

Explain the cause 0f
polarisation in a dielectric.

(b)(i)Explain the difference between coherent and non coherent detection of ON/OFF
keying SignalS

State the Carson's rule, Given that the peak deviation is 75 kHz, determine, using Carson's rule, the band widths reqUired for sinusoidal EM indexes 0f O. 25, 2.4, 5.5 and
Show that the radiation reSiStance of a small 1oop antenna is 31 200 (A/lamda2)2ohm
Explain with the help of neat diagram, the operation of a Submitt trigger employmg OP-AMP

With OP-AMP draw a a circuit ofa unity gain amplifier having no phase shift and give its one practical application
Draw the circuit of a two input adder with OP-AMP and explain its operation

(b).(i)Transformer is a constant-flux machine' justify

Explain logically why primary current increases when secondary Side is loaded

Derive a condition for maximum efficiency 0f a transformer

An ideal chopper operating with a chopping peroid of 2 in sec is supplying a load of 5 omega reSistance with inductance of 10mHenry, from a battery of 100 volts. Assume the shunt diode to proVide perfect commutation. Determine the load current waveform for the ratio TOFF,uN= 1/4 and average value of load voltage