GATE'22 EE: Daily Practices Quiz 13-NOV-2021

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GATE’22 EE QUIZ

GATE’22 EE: Daily Practices Quiz 13-NOV-2021

Each question carries 2 marks
Negative marking: 2/3 mark
Total Questions: 10
Total marks: 20
Time: 20 min.

Q1. In a DC machine, with the number poles being equal to 2, which of the following is
possible?
(a) Electrical degrees = 8 × (mechanical degrees)
(b) Electrical degrees = 2 × (mechanical degrees)
(c) Electrical degrees = mechanical degrees
(d) Electrical degrees = 4 × (mechanical degrees)

Q2. A boost converter is supplying a load of 24 W at a voltage of 12 V. If the source voltage is 6V then the source current of converter under steady state is …….
(a) 8 A
(b) 4 A
(c) 1 A
(d) 2 A

Q3. What is the value of x(t) = Sgn(t) at t = 0?
(a) -1
(b) 1
(c) Infinite
(d) 0

Q4. An oscilloscope produces Lissajous pattern with 2 vertical tangencies and 3 horizontal tangencies when fed with two frequencies to vertical and horizontal inputs.
If the vertical input frequency is 300 Hz, then the horizontal input frequency is ……
(a) 600 Hz
(b) 900 Hz
(c) 200 Hz
(d) 300 Hz

Q5. A 100 MVA, 11 KV, 3-phase, 50 Hz, 8-pole synchronous generator has an inertia constant H equal to 4 seconds. The stored energy in the rotor of the generator at synchronous speed will be:
(a) 100 MJ
(b) 12.5 MJ
(c) 800 MJ
(d) 400 MJ

Q6. For a 15-bus power system with a 3-voltage controlled bus, the size of the Jacobian matrix is
(a) 11 × 11
(b) 12 × 12
(c) 22 × 22
(d) 25 × 25

Q7. The speed regulation of a motor falls from 1100 rpm at no-load to 1050 rpm at rated load. The speed regulation of the motor is:
(a) 6.77 %
(b) 2.33 %
(c) 8.84 %
(d) 4.76 %

Q8. In a star connected three-phase balanced system. If the line current is 125A then the phase current is?
(a) 216.5 A
(b) 72.16 A
(c) 250 A
(d) 125 A

Q9. A series RLC circuit has R=4 Ω, X_L=12 Ω,X_C=9 Ω and is supplied with 200 V, 50 Hz. Calculate the power.
(a) 8000 W
(b) 6400 W
(c) 19,200 W
(d) 14,400 W

Q10. The pressure coil of an energy meter is…….
(a) Purely resistive
(b) Purely inductive
(c) Highly resistive
(d) Highly inductive

SOLUTIONS

S1. Ans.(c)
Sol. Өe=P/2×Өm=2/2×Өm
⇒ Өe=Өm

S2. Ans.(b)
Sol. For boost converter: V_0=V_dc/(1-D)
ACQ: 12=6/(1-D)⇒D=0.5
And P=V_0 I_0⇒24=12×I_0
∴I_0=2 A
∴I_S=I_0/(1-D)=2/(1-0.5)=4 A

Daily Quizzes
S4. Ans.(c)
Sol. f_y/f_x =(horizontal tangencies)/(vertical tangencies)
∴300/f_x =3/2⇒f_x=600/3=200 Hz.

S5. Ans.(d)
Sol. Inertia constant(H)=(stored KE in MJ at synchronous speed)/(machine rating in MVA)
∴Stored energy=4×100=400 MJ

S6. Ans.(d)
Sol. Number of bus(n)=15
Voltage controlled bus(m)=3
∴size of Jacobian matrix=(2n-m-2)×(2n-m-2)=25×25

S7. Ans.(d)
Sol. %Speed regulation=(Nnl-Nfl)/Nfl ×100=(1100-1050)/1050×100=50/1050×100=4.76 %.

S8. Ans.(d)
Sol. for star (γ) – connection: –
Line current (IL) = Phase current (Iph )
Line voltage (VL )=√3×Phase voltage (Vph )
Or, phase voltage = (Line voltage)/√3
⇒ (Vph=VL/√3) – For star connection

S9. Ans.(b)
Sol. |Z|=√(R^2+(XL-XC )^2 )=√(4^2+(12-9)^2 )=5 Ω
∴I=V/|Z| =200/5=40 A
∴P=I^2 R=1600×4=6400 W

S10. Ans.(d)
Sol. The pressure coil of an energy meter is highly inductive while for wattmeter it is highly resistive.