Quiz Electronics Engineering 23 Oct 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 23/10/2020

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

Q1. After counting 0, 1, 10, 11 the next binary number is
(a) 15
(b) 100
(c) 110
(d) 120

Q2. Maximum theoretical conversion efficiency of a transformer coupled class-A amplifier is typically
(a) 90%
(b) 75%
(c) 50%
(d) 25%

Q3. Consider a complex exponential sequence ω_o. Suppose ω_o = 2π, then
(a) such a sequence is periodic.
(b) such a sequence is not periodic at all
(c) periodic for some value of period ‘N’
(d) some definite range N_o < n < N_1 exists for a periodic sequence

Q4. Which of the following is a unipolar device?
(a) P-N junction diode
(b) Zener diode
(c) Tunnel diode
(d) Schottky diode

Q5. A variable reluctance stepper motor is constructed of ______________ material with salient poles.
(a) Paramagnetic
(b) Ferromagnetic
(c) Diamagnetic
(d) Non-magnetic

Q6. CRC stands for __________
(a) code redundancy check
(b) code repeat check
(c) Cyclic Redundancy Check
(d) cyclic repeat check

Q7. In a microprocessor, the register which holds the address of the next instructions to be fetched is:
(a) Program Counter
(b) Accumulator
(c) Stack Pointer
(d) Instruction Register

Q8. Charge needed within a unit sphere centered at the origin for producing a potential field, V=-6r5∈_O , for r ≤ 1 is
(a) 60π C
(b) 12π C
(c) 180π C
(d) 120π C

Q9. The output waveform of a 555 Timer is:
(a) Sinusoidal
(b) Triangular
(c) Rectangular
(d) Elliptical

Q10. To separate channels in FDM receiver we have to use
(a) integration
(b) band pass filter
(c) AND gate
(d) differentiation

SOLUTIONS

S1. Ans (b)
Sol. The sequence is as following:
⇒ 02 = 010
⇒ 12 = 110
⇒ 102 = 210
⇒ 112 = 310
⇒ 1002 = 410

S2. Ans.(c)
Sol. Conversion efficiency is
% η = (1-V_min/V_CC ) × 50 %
Maximum efficiency in class A amplifier is 50% in case of transformer coupled Class – A amplifier.

S3. Ans.(a)
Sol. In any complex exponential sequence,
⇒ h(n) = e^(jω_o n)
Period is –
⇒ N = 2π/ω_o .m where, m is integer
⇒ N = 2π/2π.m
⇒ N =m
For any integer value of m, N is rational. So, sequence is periodic.

S4. Ans.(d)
Sol. Schottky diode is a unipolar device because current conduction takes place only in one direction due to majority charge carrier either electrons or holes. This class of diodes use metal-to-semiconductor junction for rectification purposes instead of PN-junctions.

S5. Ans (b)
Sol. A Variable-reluctance Stepper motor is constructed of a soft iron multi-toothed rotor, a wound stator and ferromagnetic material with salient poles. The stator is made from a stack of steel laminations and has six equally-spaced projecting poles (or teeth) each wound with an exciting coil. Rotation occurs when the rotor teeth are attracted to the energized stator poles.

S6. Ans.(c)
Sol. A Cyclic Redundancy Check (CRC) is an error-detecting code used in digital networks and storage devices to detect accidental changes to raw data. It is inserted into the frame trailer i.e. a data, to identify any error that occurred during the transmission of the data. It only detects error but do not correct them.

S7. Ans.(a)
Sol. Program Counter is used to hold the memory address of the next instruction to be fetched for execution. It is an automatic counter which increases the address of the memory when execution is completed.

S8. Ans.(d)
Sol. Given:
V=-(6r^5)/∈_O
We know that,
E = -dV/dr
and, in case of charge with in a unit sphere( i.e. r = 1)
E = 1/(4π∈_O ) . q/r^2
Now,
E = -dV/dr = (30r^4)/∈_O
and 1/(4π∈_O ) . q/r^2 = (30r^4)/∈_O
⇒ 1/4π . q/1 = 30/1 [ for r = 1]
So, q =120π Coulomb.

S9. Ans.(c)
Sol. IC555 timer is used to generate Square Wave & Pulse signal which may be rectangular in shape.

S10. Ans.(b)
Sol. Channels are separated in FDM with the help of Bandpass filters.
Band pass filter allows a band of frequencies to pass through and attenuates other frequencies.

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