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Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
GENERAL APTITUDE
Q.1Q.1Q.1Q.1Q.1 NPA is the asset that a customer borrows and holds it for a period of time without payingany interest. RBI has reduced the holding period for NPA thrice during the period 1993-2004. In 1993 it was four quarters (360 days) how many days is the holding period in2004?(a) 90 (b) 180(c) 45 (d) 270
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)
End of Solution
Q.2Q.2Q.2Q.2Q.2 Number between 1001 to 9999 how many times 37 occurs in same sequence?(a) 279 (b) 280(c) 270 (d) 299
Ans.Ans.Ans.Ans.Ans. (b)(b)(b)(b)(b)
End of Solution
Q.3Q.3Q.3Q.3Q.3 The revenue and expenditure of four companies P, Q, R, S as shown in the figure belowcompany Q earns a profit of 10% on expenditure of 2014, the revenue of Q in 2015 is________.
P Q R S45
35
ExpenditureRevenue
Ans.Ans.Ans.Ans.Ans. ()()()()()Data insufficient
End of Solution
Q.4Q.4Q.4Q.4Q.4 Stock markets _______ at the news of the coup.(a) plugged (b) plunged(c) probed (d) poised
Ans.Ans.Ans.Ans.Ans. (b)(b)(b)(b)(b)
End of Solution
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Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.5Q.5Q.5Q.5Q.5 This book, including all its chapters, ________ interesting. The students as well asinstructor ________ in agreement with it.(a) is, was (b) is, are(c) were, was (d) are, are
Ans.Ans.Ans.Ans.Ans. (b)(b)(b)(b)(b)
End of Solution
Q.6Q.6Q.6Q.6Q.6 People were prohibited ________ there vehicles near the entrance of the main administrativebuilding.(a) to park (b) to have parked(c) from parking (d) parking
Ans.Ans.Ans.Ans.Ans. (c)(c)(c)(c)(c)
End of Solution
Q.7Q.7Q.7Q.7Q.7 Select the word do : undo : : trust :(a) distrust (b) entrust(c) intrust (d) untrust
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.10Q.10Q.10Q.10Q.10 If P, Q, R, S are four individual, how many team of size exceeding one can be formedwith Q as a member?(a) 5 (b) 7(c) 8 (d) 6
Ans.Ans.Ans.Ans.Ans. (b)(b)(b)(b)(b)
End of Solution
ELECTRIC CIRCUITS
Q.11Q.11Q.11Q.11Q.11 A resistor and a capacitor are connected in series to a 10 V dc supply through a switchis closed at t = 0, and the capacitor voltage is found to cross ‘0’ voltage at t = 0.4τ(τ = time constant). The absolute value of % change required in the initial capacitorvoltage if the zero crossing has to happen at t = 0.2τ is _____.
Ans.Ans.Ans.Ans.Ans. (54.989)(54.989)(54.989)(54.989)(54.989)If initial charge polarities on the capacitor is opposite to the supply voltage then onlythe capacitor voltage crosses the zero line.Vc(t) ⇒ Final value + (Initial value – Final value) e–t/τ
0 = 10 + (–V0 – 10) e–0.4
+–
t = 0
R
C10 V10 = (V0 + 10) e–0.4
V0 = 4.918 VNow, t = 0.2τ
0 = 0.2010 ( 10)V e−′+ − −
0V ′ = 2.214
%change in voltage =4.918 2.214
100% 54.989%4.918
− × =
End of Solution
Q.12Q.12Q.12Q.12Q.12 To ensure the maximum power transfer across Vth the values of R1 and R2 will be (Diodein figure is silicon diode)
R1
Vth
+
–
R2Is
I
I < 0
(a) R1 high, R2 high (b) R1 low, R2 low(c) R1 low, R2 high (d) R1 high, R2 low
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)2
2
( )4 ( )
d y ty t
dt+ = 6x(t)
Taking Laplace transform,s2Y(s) + 4Y(s) = 6X(s)
( )( )
Y sX s
=2
6
4s +∴ Poles are at s2 + 4 = 0⇒ s = ±2j
End of Solution
Q.17Q.17Q.17Q.17Q.17 A PMDC motor is connected to 5 V at t = 0. Its speed increases from 0 to 6.32 rad/sec monotonically from t = 0 to t = 0.5s and finally settles down to 10 rad/sec. Assumenegligible armature inductance. Find the transfer function?
(a)10
1 0.5s+ (b)100.5s s+
(c)2
1 0.5s+ (d)20.5s +
Ans.Ans.Ans.Ans.Ans. (c)(c)(c)(c)(c)When the armature inductance is neglected the transfer function of PMDC motorbecomes,
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.21Q.21Q.21Q.21Q.21 For the given block diagram of the system
s1
1+ s21R s( ) C s( )
s20
20+
which of the following is true regarding order and stability of the system(a) 4th order and stable (b) 4th order and unstable(c) 3rd order and unstable (d) 3rd order and stable
Q.24Q.24Q.24Q.24Q.24 The vector function expressed byF = ax(5y – k1 z) + ay(3z + k2 x) + az(k3 y – 4x)
represent a conservative field, where ax, ay, az are unit vector along x, y, z directions,respectively the value of constant k1, k2 and k3 ________.(a) 4, 5, 3 (b) 8, 3, 7(c) 0, 0, 0 (d) 3, 8, 5
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)
F = − + + + −i x x1 2 3ˆ ˆˆ(5 ) (3 ) ( 4 )y k z z k j k y k
Q.25Q.25Q.25Q.25Q.25 The value of mutual inductance figure shows long wire carrying current 2 A placed inaway from square coil as shown in figure. The value mutual inductance will be ____. nH.
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.26Q.26Q.26Q.26Q.26 In a dielectric medium εr = 2.25 and 3ˆ ˆ ˆ2 6r zE r a a ar φ= + +
�� in cylindrical, then find volume
charge density(a) 2∈o (b) 3∈o
(c) 4∈o (d) 9∈o
Ans.Ans.Ans.Ans.Ans. (d)(d)(d)(d)(d)
D�
= o rE E∈ = ∈ ∈�� ��
D��
=3ˆ ˆ ˆ2.25 2 6o r zr a a ar φ
⎛ ⎞∈ + +⎜ ⎟⎝ ⎠
D��
= 6.75ˆ ˆ ˆ4.5 13.5oo r o zr a a a
r φ∈∈ + + ∈
Volume charge density
ρ v = D∇ ⋅�� ��
ρ v =1 1
( ) zr
D DrD
r r r zφ∂∂ ∂+ +
∂ ∂φ ∂
ρ v = 6.751 1( 4.5 ) (13.5 )oo or r
r r r r z∈∂ ∂ ∂⎛ ⎞∈ + + ∈⎜ ⎟∂ ∂φ ∂⎝ ⎠
= 21(4.5 ) 0 0o r
r r∂ ∈ + +∂
=1
(4.5 ) (2 ) 9o orr
∈ = ∈
End of Solution
ELECTRIC MACHINES
Q.27Q.27Q.27Q.27Q.27 In the given figure, the three windings having polarity as shown above, are connectedto 3-φ, balanced supply. The number of turns in the supply winding is 20, the voltageseen in winding X having N = 2 turns will be
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Ans.Ans.Ans.Ans.Ans. (46)(46)(46)(46)(46)
V4 = ∠ ° − ∠ ° − ∠ − °2(230 0 230 120 230 120 )
20= 46∠0° V
End of Solution
Q.28Q.28Q.28Q.28Q.28 A cylindrical rotor synchronous generator delivering constant active power at a constantterminal voltage, a current of 100 A at a 0.9 p.f. lagging. A shunt reactor is connectedso that the reactive power demand doubles then the new value of armature current is______ A.
Ans.Ans.Ans.Ans.Ans. (125.29)(125.29)(125.29)(125.29)(125.29)At Pconstant, Ia1 cos φ1 = Ia2 cos φ2
cos φ1 = 0.9
tan φ1 = 0.484 = QP
⇒2QP
= 0.9686 = tan φ2
cos φ2 = 0.7182∴ 100 × 0.9 = Ia2 × 0.7182⇒ Ia2 = 125.29 A
End of Solution
Q.29Q.29Q.29Q.29Q.29 A cylindrical rotor generator having internal emf 1 + j 0.7 V and terminal voltages(1 + j 00 V). The synchronous reactance is 0.7 pu whereas subtransient reactance is0.2 pu for 3-φ bolted short circuit at generator the value of subtransient generated internalemf is ______.
Q.30Q.30Q.30Q.30Q.30 4 kVA, 200/100 V, 50 Hz single phase transformer has no load core loss of 450 W. Ifhigh voltage side is energized by 160 V, 40 Hz, the core loss will be 320 W. Find thecore loss if the high voltage side is energized by 100 V, 25 Hz.
Ans.Ans.Ans.Ans.Ans. (162.5)(162.5)(162.5)(162.5)(162.5)200 V, 50 Hz, Pc = 450 Watt160 V, 40 Hz, Pc = 320 Watt100 V, 25 Hz, Pc = ? Watt
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Vf
= const. = 20050
= 16040
= 10025
So, Pc = Af + Bf2
450 = A × (50) + B × (50)2 ...(i)320 = A × (40) + B × (40)2 ...(ii)
From (i) and (ii),
45050
= A + B(50) ...(iii)
32040
= A + B(40) ...(iv)
(iii) – (iv),(9 – 8) = B(10)
B =1
10
and A = − ×19 50
10A = 4
Now at 100 V, 25 Hz,
Pc = × + × 214 25 (25)
10= 100 + 62.5 = 162.5 Watt
End of Solution
Q.31Q.31Q.31Q.31Q.31 A 3-φ, 50 Hz, 4 pole induction motor runs at no load with a slip of 1%, at full load themotor runs at a slip of 5%. The percentage speed regulation of the motor is _____.
Ans.Ans.Ans.Ans.Ans. (4.02)(4.02)(4.02)(4.02)(4.02)4 pole, 50 Hz I.M has no load slip 1%4 pole, 50 Hz I.M has full load slip 5%
Q.32Q.32Q.32Q.32Q.32 A sequence detector is designed to detect precisely 3 digital inputs, with overlappingsequence detectable. For the sequence (1, 0, 1) and input data (1,1,0,1,0,0,1,1,0,1,0,1,1,0)the output is
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.33Q.33Q.33Q.33Q.33 A synchronous generator has lossless reactance Xs. Then VA is terminal voltage and Ef
is internal emf voltage.P :P :P :P :P : If power factor is leading then always VA > Ef
Q :Q :Q :Q :Q : If power factor is lagging then always VA < Ef
Which of the statement is true?(a) P is false, Q is true (b) P is false, Q is false(c) P is true, Q is true (d) P is true, Q is false
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)
End of Solution
Q.34Q.34Q.34Q.34Q.34 A 250 DC shunt motor having armature resistance of 0.2 Ω and field resistance of 100 Ω.It draws a no load current of 5 A at 1200 rpm. The brush drop is 1 V per brush at alloperating conditions. If motor draws 50 A at fulled load and flux per pole is decreasedby 5% because of armature reaction. The speed of the motor at full load is ____ rpm.(a) 900 (b) 1000(c) 1200 (d) 1220
Ans.Ans.Ans.Ans.Ans. (d)(d)(d)(d)(d)No load current 5 A
B.R.D = 1 V per brushloaded, IL = 50 A
Rsh = 100 Ω
Ish = =2502.5 A
100Ia0 = 2.5 AIaL = 47.5 AV = Eb + IaRa + B.R.D
0.2 Ω 250 V
Eb no load = V – Ia0Ra – B.R.D= 250 – 2.5(0.2) – 1 × 2= 247.5 Volts
Eb load = 250 – 47.5(0.2) – 1 × 2= 238.5 volts
2
1
NN =
φ×
φ2 1
1 2
b
b
EE
2
1200N
=φ
×φ
1
1
238.5247.5 0.95
N2 = 1217.22 rpm
End of Solution
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Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.35Q.35Q.35Q.35Q.35 For cylindrical rotor synchronous generators which of the following statements is/arecorrect.1. VT always greater then Eg at loading load.2. VT always less than Eg at lagging load.(a) only 1 (b) only 2(c) both 1 and 2 (d) None
Q.40Q.40Q.40Q.40Q.40 A causal control system having poles at (–2, 1), (2, –1) and zeros at (2, 1) and (–2, –1).Identify the nature of transfer function.(a) Unstable, complex, all pass (b) Stable, real, all pass(c) Unstable, complex, HP (d) Stable, real, HPF
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)All pass filter because poles and zeros are mirror-image of eachother (i..e for each polethere is a mirror-image zero).Unstable because one pole in the RHS of s-plane.
⇒ H(s) = [ ( 2 ) [ (2 )](2 )] [ ( 2 )]
s j s js j s j
− − + − −− + − − − σ
–1
1
–2 2
j
=[ (2 ) [ (2 )][ (2 )] [ (2 )]s j s js j s j
+ − − −− + + +
=2 2 2
2 2 2(2 ) [4 1 4 ](2 ) [4 1 4 ]
s j s js j s j
− − − −=− + − − +
= 2
2(3 4 )(3 4 )
s js j
− −− +
Transfer function is complex.h(t) or impulse response will be also complex because poles are not occuring inconjugate pair as well as zeros are also not occuring in conjugate pair.
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.41Q.41Q.41Q.41Q.41 x(t) ∗ h(t) = y(t), where h(t) is impulse response.
⏐x(t)⏐ ∗ ⏐h(t)⏐ = z(t ) then which of the following is correct.(a) For every –∞ < t < ∞, z(t) ≤ y(t) (b) For every –∞ < t ≤ ∞, z(t) ≥ y(t)(c) For some –∞ < t < ∞, z(t) ≤ y(t) (d) For some –∞ < t ≤ ∞, z(t) ≥ y(t)
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.42Q.42Q.42Q.42Q.42 A signal x(n) is given by 1 1( )2
n
n⎛ ⎞⎜ ⎟⎝ ⎠
where,
1 01( )
0 0
nn
n≥⎧
= ⎨ <⎩
Z-transform x(n – K) is 1,
11
2
KZ
Z
−
−− then what will be ROC of x(n – K)
(a) 12
Z > (b) Z < 2
(c) Z > 2 (d) 12
Z <
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)
x(n) = 1 ( )2
n
u n⎛ ⎞⎜ ⎟⎝ ⎠
, ROC of x(n) : 12
z >
( ) ( )n K X z−x ���⇀↽��� =11
12
KZ
Z
−
−−, ROC of x(n – K) :
12
Z >
For x(n – K) ROC will be 12
Z > .
End of Solution
Q.43Q.43Q.43Q.43Q.43 If xA and xR are average and rms values of signal x(t) = x(t – T) respectively.yA and yR are average and rms value of signal y(t) = Kx(t) respectively.K and T are independent of t.(a) yA = KxA, yR = KxR (b) yA ≠ KxA, yR = KxR
(c) yA = KxA, yR ≠ KxR (d) yA ≠ KxA, yR ≠ KxR
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)Given that,⇒ Average x(t) = Xa , Rms x(t) = XR
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
⇒ YR = RK X
Assuming K as real and positive,YR = KXR
End of Solution
Q.44Q.44Q.44Q.44Q.44 Which of the following statement is true about the two sided Laplace transform?(a) It exists for a signal that may or may not have Fourier transform.(b) It has no poles for any bounded signal that is non-zero only inside a finite time interval.(c) If a signal can be expressed as a weighted sum of shifted one sided exponentials,
then its Laplace transform will have no poles.(d) The number of finite poles finite zeros must be equal.
Ans.Ans.Ans.Ans.Ans. ()()()()()
End of Solution
POWER SYSTEMS
Q.45Q.45Q.45Q.45Q.45 A 50 Hz, power system network is operated under load of 100 MW. When the load isincreases, the power input by the synchronous generator is increases by 10 MW andfrequency of the rpm fall to 49.75 Hz. What will be the load an power system for thefrequency falls to 49.25 Hz?
Ans.Ans.Ans.Ans.Ans. (130)(130)(130)(130)(130)Assumed full load frequency is 50 Hz
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.46Q.46Q.46Q.46Q.46 Find admittance matrix 2 bus is connected by 2 transformers having ratios 1 : Ti andTj : 1 respectively and line having Y admittance.
1 : Ti Tj : IY
(a)
2
2
j
j j
T TT
TT T
⎡ ⎤−⎢ ⎥⎢ ⎥−⎣ ⎦
i i
i(b)
2
2
j
j j
T TT
TT T
⎡ ⎤−⎢ ⎥⎢ ⎥−⎣ ⎦
i i
i
(c)2
2
j j
j
TT T
T TT
⎡ ⎤−⎢ ⎥⎢ ⎥−⎣ ⎦
i
i i(d)
2
2
j j
j
TT T
T TT
⎡ ⎤−⎢ ⎥⎢ ⎥−⎣ ⎦
i
i i
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)I = Y(TiVi – VjTj)Ii = Ti I
= Ti2YVi – TiTjYVj
Ij = –Tj I Vi
Ii
Vj
I Ij
Y1 : Tx Tj : 1
= –IiTjYVi + Tj2YVj
⎡ ⎤⎢ ⎥⎢ ⎥⎣ ⎦
iII j
=⎡ ⎤− ⎡ ⎤⎢ ⎥ ⎢ ⎥⎢ ⎥− ⎣ ⎦⎣ ⎦
i i i
i
2
2
j
jj j
T Y TT Y VVTT Y T Y
End of Solution
Q.47Q.47Q.47Q.47Q.47 A transmission line is being protected by distance protection. 80% of the line is beingprotected. The transfer reactance is 0.2 p.u. A solid 3-φ, fault occurred at the end ofthe transmission line. The minimum level of fault current to activate the relay(a) 6.25 (b) 5(c) 1.25 (d) 3
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)
If = =1 10.2ThZ
= 5 pu for 100% of line
Zl = 0.2 p.u.
80%
Relay is operated for 80%Zf = 0.8 Zl ⇒ 0.8 × 0.2 = 0.16 p.u.
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.48Q.48Q.48Q.48Q.48 Voltage at bus 1 = 1.1 p.u.Voltage at bus 2 = 1 p.u.
Q12
1 2jX
Voltage at bus 2 is kept constant, Q12 is the sending reactive power from 1 to 2.On changing the bus 1 voltage, Q12 increases by 20%.Active power is zero in both the condition find the new value of bus 1 voltage.
Ans.Ans.Ans.Ans.Ans. (#)(#)(#)(#)(#)A
End of Solution
POWER ELECTRONICS
Q.49Q.49Q.49Q.49Q.49 In AC voltage controller shown below. Thyristor T1 is fired at α and T2 is fired at 180° + α.To control the output power over range 0 to 2 kW. The minimum range of variation inα is
10 –60° ∠ Ω
T1
T2200 V,50 Hz
(a) 0° to 60° (b) 0° to 120°(c) 60° to 120° (d) 60° to 180°#
Ans.Ans.Ans.Ans.Ans. (d)(d)(d)(d)(d)
End of Solution
Q.50Q.50Q.50Q.50Q.50 A 1-φ, fully controlled rectifier is connected to highly inductive RL load with R = 10 Ωat 230 V, 50 Hz. The source inductance is 2.28 mH. If the firing angle α = 45°, thenthe overlapping angle will be
Q.51Q.51Q.51Q.51Q.51 Value of σ adjusted so that 3rd harmonic is completely eliminated. Find the percentagemagnitude of 5th harmonic w.r.t. fundamental component at this condition.
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.52Q.52Q.52Q.52Q.52 A single-phase, 50 Hz full bridge rectifier with highly inductive RL load. The two mostdominant frequency components will be(a) 50 Hz, 150 Hz (b) 50 Hz, 100 Hz(c) 150 Hz, 250 Hz (d) 50 Hz, 0 Hz
Ans.Ans.Ans.Ans.Ans. (a)(a)(a)(a)(a)1-φ full bridge rectifier,
is
n = 1, 3, 5, ...f = 50, 150, 250 dominant
End of Solution
Q.53Q.53Q.53Q.53Q.53 A DC-DC converter shown below having switching frequency of 10 kHz with duty ratio0.6. All the components are ideal and initial inductor current is zero. Energy stored inthe inductor (in mJ) at the end of 10 switching cycles is
Memory Based Questions of GATE 2020Electrical Engg. | Forenoon Session
Q.58Q.58Q.58Q.58Q.58 The number of purely real elements in lower triangular representation of given 3 × 3 matrixobtained through given decomposition is