UPPSC-LECTURER'21 EE: Daily Practices Quiz 02-Oct-2021

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UPPSC Technical Education Teaching Exam Notification 2021

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UPPSC-LECTURER’21 EE: Daily Practices Quiz

UPPSC-LECTURER’21 EE: Daily Practices Quiz 02-Oct-2021

Each question carries 3 marks.
Negative marking: 1 mark each or 1/3rd
Total Questions: 06
Time: 08 min.

Q1. When supply voltage to a 3-phase squirrel cage induction motor is reduced by 20%, the maximum torque will decrease by
(a) 10 %
(b) 20%
(c) 36 %
(d) 40 %

Q2. A 10-bit D/A converter gives a maximum output of 10.23 V. the resolution is
(a) 25 mV
(b) 20 mV
(c) 15 mV
(d) 10 mV

Q3. A linear time invariant control system with unsatisfactory steady state error is to be compensated. Which is/are the correct type of cascade compensation to be provided?
1. Lead
2. Lag
3. Lag-lead
Select the correct answer using the codes given below:
(a) 1, 2 and 3
(b) 1 only
(c) 2 only
(d) 3 only

Q4. The number of address lines required to address a memory size of 16K is:
(a)16
(b) 14
(c) 12
(d) 15

Q5. Skin effect occurs when a conductor carries current at………frequencies.
(a) Medium
(b) High
(c) Low
(d) Very low

Q6. What are the average and RMS values of half wave rectified output if peak voltage is 5 V?
(a) 1.59 V, 2.5 V
(b) 3.18 V, 2.5 V
(c) 1.59 V, 5 V
(d) 3.18 V, 5 V

SOLUTIONS

S1. Ans.(c)
Sol. T_max α V^2
According to the question, voltage is reduced by 20%, i.e., V2=0.8 V1
∴Tm2/Tm1 =(V2/V1 )^2=0.64
So Tmax2 is reduced by 36 %.

S2. Ans.(d)
Sol. Resolution=Vm/(2^N-1)=10.23/(2^10-1)=10.23/1023=10 mV

S3. Ans.(c)
Sol. steady state error is reduced by Lag compensator.

S4. Ans.(b)
Sol. memory size=16K=16×1024 bytes=2^4×2^10=2^14 bytes
So, the number of address lines required to address a memory size of 16K is 14.

S5. Ans.(b)
Sol. The non-uniform distribution of electric current over the surface or skin of the conductor carrying a.c is called the skin effect. In other words, the concentration of charge is more near the surface as compared to the core of the conductor.
Factors affecting skin effect
Frequency – Skin effect increases with the increase in frequency.
Diameter – It increases with the increase in diameter of the conductor.
The shape of the conductor – Skin effect is more in the solid conductor and less in the stranded conductor because the surface area of the solid conductor is more.
Type of material – Skin effect increase with the increase in the permeability of the material (Permeability is the ability of material to support the formation of the magnetic field).

S6. Ans.(a)
Sol. For half-wave rectifier: V_avg=V_m/π=5/3.14=1.59 V
And Vrms=Vm/2=5/2=2.5 V