Quiz Electronics Engineering 10 Aug 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 10/08/2020

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

Q1. Which of the following has the greatest mobility?
(a) Positive ion
(b) Negative ion
(c) Electron
(d) Hole

 

Q2. The discrete-time equation y(n + 1) + 0.5y(n) = 0.5x(n + 1) is NOT attribute to a
(a) memoryless system
(b) time-varying system
(c) linear system
(d) causal system

 

Q3. A message signal m(t) = Amsin(2πfmt) is used to modulate the phase of a carrier Accos(2πfct) to get the modulated signal y(t) = Accos(2πfmt + m(t)). The bandwidth of y(t)
(a) depends on Am but not on fm.
(b) depends on both Am and fm.
(c) depends on fm but not on Am.
(d) does not depend on Am or fm.

 

Q4. The sum of two or more arbitrary sinusoids is
(a) always periodic
(b) periodic under certain conditions
(c) never periodic
(d) periodic only if all the sinusoids are identical in frequency and phase

 

Q5. The amplitude spectrum of a Gaussian pulse is
(a) uniform
(b) a sine function
(c) an impulse function
(d) Gaussian

 

Q6. In a VSWR measurement, a square law detector is used to detect the signal level. The voltmeter reads maximum and minimum as 64 mV and 16 mV respectively. The VSWR of the system will be
(a) 4
(b) 2
(c) 8
(d) 16

 

Q7. The JFET can operate in
(a) depletion mode only
(b) enhancement mode only
(c) either depletion or enhancement mode at a time
(d) both depletion and enhancement mode simultaneously

 

Q8. What will be the total resistance of the given circuit?

(a) 200 Ω
(b) 125 Ω
(c) 50 Ω
(d) 150 Ω

 

Q9. Compared to a CISC processor, a RISC processor has –
(a) reduced cache memory
(b) reduced number of interrupts
(c) less number of instructions
(d) reduced address lines

 

Q10. What does the Boolean expression AD+ABCD+ACD+A ̅ B+AC ̅ D+(A ) ̅B ̅ become on minimization?
(a) A+D
(b) AD+A ̅
(c) AD
(d) A ̅+D

 

SOLUTIONS

S1. Ans.(c)
Sol. Positive and negative ions are immobile ions so they don’t move. So, Electron has the greatest mobility.

 

S2. Ans.(a)
Sol. . For any system to be dynamic it must have memory. Here, the output value of the independent variable at a given time not depends only on the input at the same time , so the system is not memoryless.

 

S3. Ans.(b)
Sol. Given:
Amplitude of message signal = Am
Frequency of message signal = fm

We know that,
Phase sensitivity = Kp
BW of PM signal(BW) = 2(Δf + fm)
and frequency deviation(Δf) = Am Kp fm

Now, BW = 2( Am Kp fm + fm) = 2( Am Kp + 1)fm

Therefore, The bandwidth of y(t) depends on both fm and Am.

 

S4. Ans.(b)
Sol. The sum of two or more arbitrary sinusoids is periodic if the ratio of the sinusoids is rational number. So, under certain condition the signal is periodic.

 

S5. Ans.(d)
Sol. The Fourier transform of a Gaussian signal in time domain is also Gaussian signal in the frequency domain.
Fourier transform is
e^(〖-πt〗^2 ) □(↔┴(Fourier Transorm) ) e^(〖-πf〗^2 )

 

S6. Ans.(a)
Sol. Given:
V_max = 64 mV
V_min = 16 mV

Now,
VSWR = V_max/V_min
⇒ VSWR = 64/16
So, VSWR = 4

 

S7. Ans.(a)
Sol. JFET operates in depletion mode only because it works only when a reverse voltage VGS is applied between the gate and source and due to this VGS, the width of the depletion layers increased. Channel width and drain current both decrease so it operates only in depletion mode.

 

S8. Ans.(c)
Sol. Two resistors of 50 Ω are connected in series and in parallel with 100 Ω resistor.
The equivalent resistance is
⇒ R_eq = (50 + 50) || 100
⇒ R_eq = 100 || 100
⇒ 1/R_eq =(100 × 100)/(100 + 100)
⇒ 1/R_eq =10000/200
So, R_eq = 50 Ω

 

S9. Ans.(c)
Sol. CISC stands for “Complex Instructions Set Computing” and RISC stands for “Reduced Instructions Set Computing”. Hence, a RISC processor has less number of instructions.

 

S10. Ans.(a)
Sol.
AD+ABCD+ACD+A ̅ B+A C ̅ D+ A ̅( B) ̅
= AD+ABCD+ACD+A C ̅ D+ A ̅( B) ̅ + A ̅ B
=AD(1+AB+C+C ̅ )+A ̅(B+B ̅)
=AD+A ̅ [∵ B+B ̅ =1]
=AD+(A ) ̅(1+D) [∵ 1 = 1 + D]
=AD+A ̅D+A ̅
=A+D(A+A ̅)
=A+D

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