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1
CB
VB
EF
Detailed solution of IES 2014 (ECE) objective Paper I : Set A
1. (B)
2. (C) V E V E
3. (C) The phenomenon of breakdown in solids is most complicated one and is least understood.
Following three kinds of breakdown are possible in solid dielectrics.
(1) Electrothermal breakdown.
(2) Purely electrical breakdown
(3) Electrochemical breakdown
4. (C) H
1R
n.e
For Metal n = HR 0
5. (C) V 12Volt
P 30 Watt
P V.I I 2.5 A
Q I.t 2.5 60
Q 150C
6. (B) At very high temperature
N-type s.c. becomes Intrinsic s.c.
7. (A)
8. (C) 0.785 4 3.240
9. (A) e r 1
10. (C) Ferromagnetic property is explained on the basis of Domain Theory.
11. (C) Saturation magnetization is higher in Ferrite but less than Ferromagnetic material
12. (A) 5m 10
So diamagnetic is very small & ve.
13. (B) It is property of ferromagnetic material which causes to close their shape or dimension this
occurs due to process of magnetization.
14. (C) Most commonly used material for electrolytic cap in as dielectric is Aluminum oxide.
Mostly used are :
1. Aluminum oxide thin film (7 8)
2. Mica
3. Porcealin
4. Polyethylene
5. Mylar
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2
1
2
1
2 2
1
9 9 9
15. (D)
Here every C has 6 F value.
16. (B) V 2000
Ed 1cm
5E 2 10 V/m
19 5
14
F qE 1.6 10 2 10
3.2 10 N
17. (B) 2Q
U2C
2
3
6
Q10 10
2 100 10
2 2 4Q 2 10 10
3Q 1.414 10 C
18. (B) CF CD
NE E KT n
N
For Degenerate S.C. C
D
N1
N
D
C
N1
N
DN Conc of es in V.B
CN Density of states in C.B
19. (B) 173.8 10 ohm.m
20.0012m / V sec
315mm 15 10 met
I = 25 A
B = 0.6 T
11HV.m
R 3.16 10A.T
HHB.I.RB.I
Vn.e.
0.6
25 113.16 10
15
310
8HV 3.16 10 Volt
20. (C) Zener diode is used as a constant voltage regulator.
-
3
+
Vo
+
V = 0GS
VDS
Pinch off
ID
21. (D) mrms
VV
2
mV 9 2
m02V 18 2
V DC
8.1 Volt
22. (B) mV 800
50825
m
50 825V 51.5
800
23. (C)
3
ac
1.5 0.5 10 A
20 A
= 50
24. (D) By use of schottky diode storage delay time is reduced.
25. (D)
26. (A)
27. (B) Hb'e
1f
2 r c
ie bb' b'eh r r
For higher Hf b 'er shd be small
So for given ie bb'h , r shd be less
28. (D) For Transistor to be work as a switch it must move form cut off to saturation and saturation
to cut off
it is used for lose signal condition which makes transistor into saturation
29. (D) In NPN es move from E to C while in PNP hole moves from E to C but es have higher
mobility than holes
30. (B) EB Junction is F. biased & CB Junction is reverse biased
31. (B) Above Pinch off drain current becomes practically constant.
32. (B) 2 CCB1 2
R .V 1500 18V
R R 4700 1500
= 4.35 V
-
4
ts
Gate current
Anode current
T/2 T/2
1
F.T
33. (B)
34. (B)
35. (C) SCR can be brought back to forward blacking state from conduction state only by reducing
the forward current to a level below that of holding current this can be done by :
1. Natural comm.
2. Forced comm.
SCR are made turned off by commutation methods Turn off time of SCR is time required to
achieve forward blocking capability after commutation is initiated.
Turn off time of SCR varies from (5 200) sec then turn off time of commutation circuit is
called circuit turn off time (tc) and hence circuit turn off time must be greater than turnoff
time of SCR (tc > tq)
36. (B) y t x 2t x 3t
it is linear & causal.
37. (A) m
j
y m x j
y m y m 1 x m
Accumulator is linear & Time In Variant System.
If x m m then y m h m
So h m u m
For stability m m
h m u m
=
So system is not stable.
38. (A)
39. (C) mrmsI
I3
2 2
2 mrms
I 9P I .R .R 20 540Watt
3 3
40. (B) 10 3in 1.5 10 / cm
15 3p 2.25 10 / cm
-
5
1.0
F (x)X
x
2 5 3in.p n n 10 / cm
41. (C) For existence of Fourier series it must follow Dirchlet conditions :
(i) Finite no. of maxima or minima
(ii) Finite no. of discontinuities
(iii) Absolutely integrable
So if a periodic function satisfies Dirchelet conditions then it can be represented by Fourier series.
42. (A) Properties in time domain & frequency domain are same.
43. (*) pr
r l d
GR 73
R R 80 G
d80 16
G 17.5373
d 10G in dB 10 log 17.53 12.4dB
44. (A) For a causal system
h t 0 for t < 0
45. (C) ROC will be z 1/2 & | z | 1/3
So common ROC will be
| z | 1/2
46. (C)
47. (A)
1
1
d z dz 1H z
1 dz z d
Zero is located at z 1/d
Pole is located at z d
| d | 1 so 1st pole then zero
So it is a phase lag compensator and hence it is a low pass filter.
48. (B) It is a non decreasing function
c.d.f. of a discrete R.V. has always
Values less than 1.
49. (A) P X C is basically p.d.f not c.d.f here this value will be Xf x 0 for all x.
Since between a & b there are uncountable values so we can assume values between
Minus infinity and infinity and hence value will be zero for having area equal to 1 .
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h(t)x(t)
y(t)
+
V
R
R
I
50. (B) Random Variable is a mathematical function which maps all the elements of random sample
space on a real line or same part of it. So it should not be complex and the values assigned
by random variable are deterministic.
51. (D) For a wide-sense stationary process correlation function is depends upon time difference only
So it will be always symmetric.
52. (C)
53. (B)
E Y h d . E X
If E[X] is zero then E[Y] will be zero.
If input has WSS then output will also be WSS.
54. (B) Superposition theorem is valid for ac and dc circuits only.
55. (A) If independent source becomes doubled then current will become doubled.
56. (A) C1 1
XWC 2 fC
if cf 0 X
c 61
f 50Hz X2 3.14 50 10 10
318.47
57. (B)
58. (A) LX L 2 fL
LX if both f and L
59. (C) V 282.84sin 377t6
mV 282.84
mrmsV 282.84
V 200Volt2 2
377
377 Rad/ sec f 60Hz6.28
1 1
f T 0.0167secT 60
60. (B) 1
I Vdtc
integration of square wave is a triangular wave.
61. (B) If input is given in sinusoidal then in steady state (o/p) will have sinusoidal nature but with
diff. amp. & phase.
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L = 0.01H
v(t) = 283 sin(300t + 90)
62. (C) V 283 90
300 Rad / sec
V
IZ
1
283 90I
5 tan 3/4
1
Z 4 j 300 0.01
4 3j
56.6 90 tan 3/4
So i t 40 2 sin 300t 53.13
63. (C) 2rmsP I R
2rms10 I 5
mrms
II 2
2
mI 2A
m
V 50 0
I I 0
50 0 50 0I
15 j L | z | 0
Here 50
z (1)| z |
but 15 15
cos 0.6| z | 25
64. (A) Connected graph means at least there must be at least one path between 2 nodes.
65. (B) Twig matrix has either value 1
Twig matrix is square matrix. Link matrix may be square or rectangular matrix
66. (B)
67. (D) A BA 1 Z Y
AB Z
B BC Y 1/ Z
D = 1
68. (C) A B A B
C D C D
69. (B) t 2tS t Ae Be C
if dS
h tdt
is applied then S(0) = 0
t 2th t Ae 28e
so A 4, B 3
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8
R
at S = 0z(0) = 1
I
S 0 0 4 3 C 0 C 1
70. (A)
71. (B)
2
k s 4z s
s 2 25
if k 4
s 0 z 0 129
so 29
k4
at s 0 z 0 1
so R 1
72. (D) Since z(s) has II order terms in r rN & D hence it will be RLC circuit
73. (B)
74. (A)
75. (B) Electric field of lines never form closed loop.
76. (A) Maxwells divergence equation is .B 0
77. (B) I
H2 r
7
0
2
I 4 10 5B
2 r 2 5 10
52 10 T 20 T
78. (B) Time varying magnetic field generates time varying electric field & vice versa.
79. (C) For free space = 0
H j E
.D 0
80. (B) .B 0 means no magnetic pole exists.
81. (C) maxE E sin kx t
max maxmax
E 100120 & H
H 120
7max100
B 4 10120
82. (C) C2a
m
For Dominant mode it must be TEM mode
so m 1 C 2a
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f (10)c
L(dB)
0
83. (B) 1
3
PC 20dB 10log
P
1
3
P100
P
So 3
3
100100 P 1mW
P
84. (C)
85. (C)
R j LZ
G j C
For Low loss R = 0 & G = 0
So R
-
10
R
30mA300V
+
94. (D) 2
c d
I dL
2 d
2
5I dL. 6 102 d
2
520 dL
. 6 102 d
5 7dL 12
10 3 10 H / Rad 0.3 H / Radd 400
73 10 H / Rad 0.3 H / Rad
95. (C) If A is true value of measurement quantity and A is result of measurement then Absolute
error A A = 80 79 = 1.0 Volt
96. (C) I = 2 0.5%
R = 100 0.2%
2P I R P I R
100 2 100%P I R
2 0.5 0.2
1.2%
97. (C) Power = V.I
P V I
100% 100% 100%P V I
100 1502% 2%
40 75
9%
98. (C) % Limiting error 150
1%9
150
% 16.7%9
99. (C)
msh
R 10R 0.010
m 1 1000 1
100. (D) Potential diff across terminal of cell remains at 1.5 V-0.15x2=1.2 V only.
101. (B)
3 3300 3 30 10 R 30 10
3 310 3 10 R 10
R 3 10,000
R 9997
102. (B) 1
1
z a *H z
1 az
Put jz re
Discrete time frequency response will be aperiodic and does not depend upon .
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Vs I
Rs
103. (D) Absolute encoder provides digital value as an o/p signal.
Here output is in binary form which is proportional to angle of shaft.
104. (D)
105. (B) P
n 60T
300060
120
1500 RPM
106. (B) Voltage 30.02V.met 20 10
N
3
2
N2 10
m
40 0.02Volt
0.8V
107. (A)
108. (B)
109. (A) A Thermocouple is a type of temperature sensor which is made by joing two dissimilar
metals at one end.
The joing end is referred as hot junction the other end of these dissimilar metals is referred as
cold end or cold Junction.
The last pt. of thermocouple is known as cold junction. The amount of o/p produces is det. by
difference b/w hot & cold Junction temp.
The cold Junction temperature must be known to accurately determent the temp.
110. (B) 0.003 100%
1.5
0.3
0.2%1.5
111. (C) Hard magnetic materials have large hysteresis loop area.
112. (B) In Ge it is of the order of 0.01 eV which make es free for conduction.
113. (D) FET is a voltage controlled current device.
114. (A)
115. (A)
116. (A) dV
I Cdt
117. (B) Due to presence of 0sin t it will not converge.
118. (D) Helical antenna does not have the largest B.W, high directivity
119. (B) s D
s
V VI
R
sV Supply voltage
DV Voltage drop across LED
sR Current limiting resistor
out F
s
F
V peak VR
I
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outV peak Peak o/p voltage
FV LED Volt drop
FI LED Current drop
Since voltage drop across diode dep. upon value of current through it, therefore it controls the
amount of light output (or brightness) of LED.
In order to avoid fluctuations in the brightness current this LED must be kept constant.
120. (D)