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

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 .

6

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.

7

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

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

9

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 .

11

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

12

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)