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Quiz Electronics Engineering 21 Sep 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 21/09/2020

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

Q1. If X(ω) = ?(ω – ω_o), then x(t) is
(a) e^(-jω_o t)
(b) ?(t)
(c) 1/2π e^(jω_o t)
(d) 1

Q2. The waveguide modes are usually excited from a signal source through
(a) a coaxial cable
(b) an aperture
(c) an antenna
(d) free-space coupling

Q3. Which of the following is used for serial access storage –
(a) RAM
(b) Magnetic Tape
(c) Magnetic Disk
(d) Core Memory

Q4. The hexadecimal equivalent of 1110011011110101 is
(a) E67F
(b) E76F
(c) E7F5
(d) E6F5

Q5. What is SIM in microprocessor?

Q6. A sinusoidal signal of amplitude A is quantized by a uniform quantizer. Assume that the signal utilities all the representation levels of the quantizer. If the Signal to Quantization ratio is 31.8 dB, the number of levels in the quantizer will be
(a) 32
(b) 16
(c) 64
(d) 8

Q7. The voltage in a circuit follows the law V = 100 sin⁡ωt. If the frequency is 25 Hz, how long will it take for the voltage to rise to 50 volts?
(a) 1/50s
(b) 1/100s
(c) 1/300s
(d) 1/600s

Q8. The fourier transform of a function is equal to its two-sided Laplace transform evaluated
(a) on the real axis of the s-plane
(b) on the imaginary axis of the s-plane
(c) on a line parallel to the real axis of the s-plane
(d) on a line parallel to the imaginary axis of the s-plane

Q9. The Address Resolution Protocol (ARP) is used for
(a) Finding the IP address from the DNS
(b) Finding the IP address of the default gateway

Q10. The transconductance is measured in
(a) mhos
(b) amperes
(c) ohms
(d) volts

SOLUTIONS

S1. Ans.(c)
Sol. In Fourier Transform –
e^(+jω_o t).x(t) ↔┴( F.T ) X(ω – ω_o)
1 ↔┴( F.T ) 2π?(ω)
Now,
e^(+jω_o t).1 ↔┴( F.T ) 2π?(ω – ω_o)
⇒ 1/2π e^(+jω_o t) ↔┴( F.T ) ?(ω – ω_o)

S2. Ans.(a)

S3. Ans.(b)

S4. Ans.(d)
Sol. We know that one digit in Hexadecimal is equivalent to 4 binary digits.
Here, Grouping binary numbers in a group of 4 we get,
⏟1110┬(↓┬E ) ⏟0110┬(↓┬6 ) ⏟1111┬(↓┬F ) ⏟0101┬(↓┬5 )
Therefore, The hexadecimal equivalent of 1110011011110101 is E6F5.

S5. Ans.(b)
Sol. SIM stands for Set Interrupt Mask which is handling the interrupts in 8085 microprocessors.

S6. Ans.(a)
Sol. Given:
SQNR = 31.8 dB
SQNR of a uniform quantized sinusoidal signal is given by
SQNR in dB = 1.8 + 6n where, n is number of bits
Now,
31.8 = 1.8 + 6n
⇒ 6n = 31.8 – 1.8 = 30
∴ n = 5
Therefore, Number of quantized level = 2n = 25 = 32

S7. Ans.(c)
Sol. Given:
V = 50 Volt
f = 25 Hz
Here,
⇒ ω = 2πf = 2π × 25
∴ ω = 50π
Now,
⇒ 50 = 100sinωt
⇒ sinωt = 50/100 = 1/2
⇒ ωt = π/6
⇒ 50πt = π/6
⇒ t = π/(50π × 6)
So, t = 1/300 sec

S8. Ans.(b)
Sol. Relation between Fourier Transform and Laplace Transform: –
As s = σ + jω
F(σ + jω) = ∫_(-∞)^∞▒〖f(t)〗 e^(-σt) e^(-jωt)dt = e^(-σt)F(ω)
When σ = 0, then LT becomes FT.

S9. Ans.(d)
Sol. ARP discovers the hardware address, also called Media Access Control (MAC) address of a host from its known IP address.

S10. Ans.(a)
Sol. The unit of transconductance is similar to unit of conductance. It is measured in Siemens also represented as mho.

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