Quiz Electronics Engineering 27 July 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 27/07/2020

Each Question carries 1 Mark
Negative Marking: 1/4
Time: 10 Minutes

Q1. Which of the following does not cause permanent damage to an SCR?
(a) High current
(b) High rate of rise of voltage
(c) High temperature rise
(d) High rate of rise of current

Q2. The VSWR of a transmission line is
(a) directly proportional to load impedance and inversely to characteristic impedance
(b) directly proportional to characteristic impedance and inversely to load impedance
(c) proportional to load and characteristic impedances
(d) directly to voltage minimum and inversely to voltage maximum

Q3. In a PCM system each quantization level is encoded into 8 bits. The signal to quantization noise ratio is equal to
(a) 24 dB
(b) 50 dB
(c) 64 dB
(d) 256 dB

Q4. In Boolean algebra, A + A + A + ….. + A is the same as
(a) zero
(b) A
(c) n A
(d) A^n

Q5. Transient current in a circuit results from
(a) Voltage applied to the circuit
(b) Impedance of the circuit
(c) Resistance of the circuit
(d) Changes in the stored energy in inductors and capacitors

Q6. BCD numbers are obtained by
(a) converting binary to decimal
(b) each decimal digit is represented by a four-bit binary
(c) converting decimal number to binary
(d) converting decimal to octal numbers

Q7. X-band frequencies are in which one of the following ranges?
(a) 3.5 to 5.5 GHz
(b) 5.5 to 8.0 GHz
(c) 8.0 to 12.0 GHz
(d) 12.4 to 16.4 GHz

Q8. A read bit can be read
(a) by CPU and written by the peripheral
(b) and written by CPU
(c) and written by peripheral
(d) by peripheral and written by CPU

Q9. Which one of the following is not a LED material?
(a) GaAs
(b) GaP
(c) SiO2
(d) SiC

Q10. Two waves of the same frequency have opposite phase when the phase angle between them is
(a) 360°
(b) 180°
(c) 90°
(d) 0°

SOLUTIONS

S1. Ans.(b)
Sol. If there is higher rate of increase in applied voltage then the SCR is not damaged permanently. SCR is triggered ON due to large applied voltage so it is not damaged.

S2. Ans.(c)
Sol. Standing Wave Ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. SWR in terms of maximum and minimum AC voltage is called VSWR. VSWR is also the ratio of maximum to minimum voltages.

S3. Ans.(b)
Sol. Given:
Number of bits(n) = 8

We know that in PCM,
S/N_q (dB)=(1.8 + 6n)dB where, n is number of bits

Now, S/N_q =( 1.8+6×8 )
= 49.8 dB ≈ 50 dB

Therefore, The signal to quantization noise ratio is equal to 50 dB.

S4. Ans.(b)
Sol. We know, A + A = A

S5. Ans.(d)
Sol. Transient occurs due to the sudden release of stored energy either in inductor or capacitor. Transient may be either due to both high Voltage or high Current.

S6. Ans.(b)
Sol. In Binary Coded Decimal (BCD) each decimal digit is represented by a 4-bit binary number because BCD Number is from 0 to 9, which requires four bits to store. It is also called as 8421 code.

S7. Ans.(c)
Sol. Table of frequency band and their respective frequencies range –
Frequency Band Frequency range(in GHz)
HF 0.003 – 0.030
VHF 0.030 – 0.300
UHF 0.300 – 1.000
L band 1 – 2
S band 2 – 4
C band 4 – 8
X band 8 – 12
Ku band 12 – 18
K band 18 – 27
Ka band 27 – 40
Millimeter 40 – 300
Submillimeter > 300

S8. Ans.(a)
Sol. A read bit is read by CPU and this process is done in the CPU and written by peripheral like Monitor Screen.

S9. Ans.(c)
Sol. SiO2 is an insulating material used in MOSFET for preventing current loss though gate.

S10. Ans.(b)
Sol. When the phase difference between two waves is 1800 (it may be = + 1800 or – 1800), then the waves are said to be in opposite phase.

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