PAPER-II ELECTRONIC SCIENCE Signature and Name of Invigilator
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D 8 8 1 3

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Number of Pages in this Booklet 8 Number of Questions in this Booklet 50 Instructions for the Candidates

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ELECTRONIC SCIENCE
Paper II

Note This paper contains fifty objective type questions of two marks each. All questions are compulsory.
4. In a p type silicon sample, the hole
1. The current i1 in the following
1015/cm3concentration is 2.25
×

network is given by



i1 40.96 mA


i1 4.096 mA


i1 4.096 mA


i1 40.96 mA



2. The velocity of propagation in a rectangular metallic waveguide is given by the relation
... ...
p2
mp

...... ....
g
p

2
mp

....
p
pmp
.






2
p

...

...

n
.2µ.


ba





2
p

...

...

n
.2µ.


ba
g
.






22
mp
p

...

...

...

...

n
.2µ.


ba
.






22

p

2p


...

...

...

n
.2µ.


ba

3. The radiative and non-radiative life times of the minority carriers in the active region of a double hetero-junction LED are 60 ns and 100 ns respectively. The internal quantum efficiency is given by

60% 62.5%


37.5% 82.5%


.

If the intrinsic carrier concentration
is 1.5
×

1010/cm3, the electron
concentration is given by

zero


1010/cm3


105/cm3


1.5 × 1025/cm3



5. A signal 5 sin (2p 100t) frequency modulates a carrier. The resulting FM signal is {10 cos (2p 105t) 15 sin (2p 100 The approximate bandwidth of FM signal is

0.1 kHz 1 kHz


3.2 kHz 4 kHz



6. What is the Octal equivalent of thebinary number 11111001

761 762





371

372


7. The block diagram given below

is equivalent to












8. The gauge factor of a resistance wire strain gauge is a measure of

Sensitivity of the gauge


Resolution


Dynamic range of displacement measurement capability


Variable inductance



9. In an LVDT, the two secondary wind map are connected in differential to obtain

higher output voltage


an output voltage which is phase sensitive, i.e., the o/p voltage has a phase which can lead up to a conclusion whether the displacement of the core took place from right to left or from left to right.


in order to establish a null or the reference point for the replacement of the core.


both and



10. Microprocessor is also known as CPU. What is CPU

Control Processing Unit


Central Processing Unit


Central Progressing Unit


Control Progressing Unit



11. If is a variable, denotes

is incremented twice


is incremented once


is replaced with i 2


is multiplied by 2



12. For a SMF, following characteristic are given by
1.
0 v 2.405

2.
v 2.405

3.
Core radius is less than 10 µm

4.
Attenuation is of the order of 1 dB/km Which of the following statement is true



1 and 4 is correct.


2 and 3 is correct.


1 and 3 is correct.


3 and 4 is correct.



13. In a directional coupler, the power is applied at port 1 and output is taken from the port 2. For this following statements are given
1. Coupling coefficient is given P1
.by C 10 log10 P4
2. Coupling coefficient is P4
.C 10 log10
P1
3. Directivity is given by P4
.D 10 log10
P3
4. Directivity is given by P2
.D 10 log
P1 Which of the following statement is true

1 and 3 is correct.


2 and 3 is correct.


2 and 4 is correct.


1 and 4 is correct.



14. An AM demodulator can be implemented with
1.
A linear multiplier followed by low pass filter.

2.
A linear multiplier followed by high-pass filter.

3.
A diode followed by low pass filter.

4.
A linear multiplier followed by


band-stop filter. Which one of the following is correct

1 only 3 only


1 and 3 4 only



15. NAND Gate can also be represented by
1.
AND invert Gate


2.
OR Invert Gate


3.
Bubbled OR


4.
Bubbled AND
Which of the following is correct




2 and 3 1 2



2 4 1 3




16. In 8085 processor,
1.
AD0 AD7 are treated as input as well as output signals.

2.
HLDA is a output signal.

3.
HOLD is a output signal.

4.
SOD is a output signal.



2 and 3 are output signals.


3 and 4 are output signals.


2 and 4 are output signals.


3 and 4 are output signals



17. A variable type indicates therange and the no. of bytes.
1. 1 byte 2. 2 bytes
3. -127 to 128 4. -128 to +127

1 3 2 3


1 4 2 4



18. The hygrometer is an instrument used to measure
1. rainfall 2. altitude
3. relative humidity 4. temperatureWhich of the following is true

1 and 2 is true.


1 and 4 is true.


3 is true.


3 and 4 is true



19. Hall effect can be used to measure
1.
conductivity of the charge carrier.

2.
mobility of the charge carrier.

3.
the number of valence electrons per atom.

4.
band gap of the material. Which of the following is correct



1 and 2 are true 2 and 3 are true


3 and 4 are true 1 and 4 are true



20. In a JFET, the amplification factor transconductance and the
mdynamic drain resistance are related as g
m rd
µ µ
rd g
m
µ rd × g µ g· rd2
mm

21. Consider the following materials used for fabrication of Photonic Ics.
1. Ga P 2. In As
3. Ga As 4. Si The correct sequence of the ascending order in terms of band gapenergies is

2 and 3 2 and 3


1 and 4 3 and 1



Paper-II 4
22. Consider the following
1. Quantization 2. Sampling
3. Encoding 4. Low-pass filter The correct sequence for converting a low-pass analog signal to Digital signal is

2 3


3 1



23. Consider the following circuit configurations
1.
Common emitter

2.
Common base

3.
Emitter follower

4.
Emitter follower using Darlington pair The correct sequence in increasingorder of the input resistances of theseconfigurations is



3 3


4 4



24. 8085 microprocessor has a flagregister. The following flags are there, keep them in the ascending order starting from LSB to MSB.
1. Parity flag 2. Zero flag
3. Carry flag 4. Sign flag

3 and 4 1 and 3


1 and 4 2 and 4



25. The following logic families havetheir propagation delay. Arrangethem from lowest propagation delayto highest propagation delay.
1. TTL (Standard) 2. ECL
3. Low power CMOS 4. DTL

4 and 3 1 and 3


3 and 1 3 and 4



26. Match List-I with List-II and select the correct answer using codes given below
List I List II

Indirect band gap Ga As


Direct band gap Cavity


Laser diode (iii) Spontaneous emission


LED Si



Codes
















27. List I List II

Poisson's equation .2V O


Laplace equation fH.dl I


Ampere's Law (iii).·E ../.o


Divergence of the .2V =field


../.
Codes














D-88-13

28. 29. 30. List I List II Frequency Modulation Balanced Modulator Double sideband suppressed carrier Companding PCM Pre-emphasis and De­emphasis AM Envelope Detection Codes List I List II Non-Weighted Code 8421 Error-Detecting Code Gray Code Weighted Code Hamming Code Error-Correcting Parity Check Codes List I (Transducers) List II (Measured Quantity) Capacitive transducer Temperature Thermocouple Power Bourdon gauge Displacement Solar cell Pressure Codes 31. 32. 33. 34. List I List II Voltage regulated IC Figure of merit Bistable multivibrator CMRR OPAMP Capture range and locking range Phase Locked Loop flip-flop Codes List I List II ASK Uses two frequencies,mark and space. FSK Baud rate is same as bit rate. BPSK On-off keying QPSK Baud rate is half of bit rate Codes List I List II if statement case do statement return switch statement while main statement else Codes List I List II (Amplifiertype) (Circuit/property) RC coupling Higher voltagegain and impedence matching. Inductive coupling Ability to amplify dc and low frequency signal. Trans­former coupling Minimum possible non-linear distortion Direct coupling Low collector supply voltagescan be used. Codes
D-88-13 5 Paper-II


35. List I List II

assembler executes programline by line.


compiler creates machine code.


interpreter (iii) finds faults during execution.


debugger creates object file.


Codes















Directions Q. Nos. 36 to 45 The following items consist of two statements, one labelled the "Assertion" and other labelled the "Reason" You are to examine these two statements carefully and decide if the Assertion and the Reason areindividually true and if so, whether the Reason is a correct explanation ofthe Assertion. Select your answers tothese items using the codes givenbelow and mark your answer accordingly. Codes

Both and are true and is the correct explanation of


Both and are true, but

is not the correct explanation of


is true, but is false.


is false, but is true.



36. Assertion A reflex klystronmakes use of a single cavity.
Reason The single cavity performs the functions of buncher as well as catcher cavity.


37. Assertion LP01 is basically
HE11 mode. Reason Linearly polarisedmodes are strongly guidedmodes, in which TE and TM modes do not have identical propagation constants.

38.
Assertion Combinational circuits have no memory, timing or feed back loop.

Reason The output of combinational circuit depends on their input and previous output state.


39.
Assertion Digital base bandmodulation is also referred to as TDM.

Reason Pulse analogmodulation is first step in converting analog signal to Digital Signal.


40.
Assertion Under certain conditions, one gets peakresponse at high frequency intransformer coupled amplifiers.

Reason High frequency model of transformer coupledamplifiers is a resonant circuit.


41.
Assertion At high temperatures, the avalanche breakdown voltage of zenerdiode remains constant.

Reason At high temperatures, mean free paths of electronsand holes are shorter, therefore a larger field is required tocause ionization.


42.
Assertion Piezoelectric transducers are not suitable for ultra-low frequency vibration measurement.

Reason Piezoelectric materials have a high dielectric constant.


43.
Assertion The contents of Random Access memory is a volatile innature. As soon as the power isremoved to the IC, the contents are erased from the memory.

Reason The contents of Read-only Memory is a non-volatile in nature.


44.
Assertion Logarithms are used to change a multiplication or division problem into a simpler addition and subtraction problem.


Reason The Laplace transformenables the circuit analyst to convert the set of integrodifferential equations describing a circuit to the complex frequency domain.

45. Assertion char "paper" acts as a constant pointer to a string.
Reason "Paper" "P" acts as a pointer to a constant string.

Read the passage and answer the QuestionNos. 46 to 50 that follows based on yourunderstanding of passage.
Power devices with pnpn layers suchas SCR, SCS and GTO belong to thyristerseries. However UJT is also a member of this group. The silicon controlled rectifier is three terminal pnpnsemiconductor switching device, which is probably most important circuit element after the diode and the transistor. An SCR can be used as a controlled switch to perform various functions such as rectification inversion and regulation of power flow. It is unidirectional power switch and being extensively used inswitching ac and dc. It has capability to control power as high as 10 MW. The frequency range of its application has alsobeen extended up to 50 kHz. SCR is a rectifier with control action. The third element called gate enables the controlledrectification gate is used to turn SCR but not turn it SCR is made of Si because it has to handle high power andhigh temperature.
There are many advantages of SCR as a switch i.e. the switching speed is veryhigh up to 109 operation per second and itpermits control over a large current (30­100 in the load by means of a small gate current of few mA. SCR has two states turn ON and turn OFF state. There are two ways to turn ON keep the gate open and madethe supply voltage equal to the breakovervoltage operate SCR with supplyvoltage less than breakover voltage. Thegeneral methods used for turning the SCR OFF are anode current interruption and
force commutation. It is not advisable to turn the SCR with zero gate signal.
Some of the applications of SCR aremotor controls, relay controls, inverters, preventive circuits, regulated power supply and phase control. Another pnpn device have characteristic similar to that of SCR is SCS (Silicon Controlled Switch).
A device that can control ac power tothe load during the positive and negativecycle of input is called 'triac'. It isbasically a diac with a gate terminal for bilateral turn ON. Gate Turn OFF switch is one more pnpn device which can be turned ON or OFF with cathode gate. Some application of GTO are counters, pulse generators and multivibrators.
Light activated SCR (SASCR) isturned ON by the light falling on the gate.It is used as a relay, optical light controller,phase controller and motor control device.
46. If the applied voltage is increasedfurther when an SCR is forward biased, then

It becomes more forward biased.


It becomes more reverse biased.


It will come to state.


It will come to state. di



47. The if an SCR in an ac voltage
dt controller is high if the load is

A pure inductance


An induction motor


A pure resistance


A combination of resistance and inductance.



48. Triac can be considered as

Two SCRs connected in antiparallel with common gate.


Two SCRs connected in parallel with common gate.


Two Resisters connected in anti parallel.


Two GTOs connected in parallelwith common cathode gate.



49. Forced commutation is employedwhen anode voltage is

AC DC


Pulsating Triangular



50. Diac is

Two terminal bidirectional switch.


Two terminal Unilateral switch.


Three terminal bidirectional switch.


Three terminal unilateral switch.



Space For Rough Work
Paper-II 8
D-88-13