Quiz Electronics Engineering 7 Nov 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 07/11/2020

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

Q1. Program Counter register stores the:
(a) address of the first memory block
(b) address of the next instruction to be executed
(c) address of the last memory block
(d) size of the primary memory

Q2. In class-A amplifier utilizing a direct coupled load (resistive), the maximum conversion efficiency is
(a) 25%
(b) 90%
(c) 50%
(d) none of these

Q3. Let f(x) be the continuous probability density function of a random variable X. The probability that a < X ≤ b, is
(a) f(b-a)
(b) f(b) – f(a)
(c) ∫_a^b▒〖f(x)dx〗
(d) ∫_a^b▒〖xf(x)dx〗

Q4. Which of the following diodes is limited to the reverse-bias region in its region of operation?
(a) Schottky
(b) Photodiode
(c) Tunnel
(d) Rectifier

Q5. Media of communication between operation and operated unit is not:
(a) OFC
(b) Signaling copper cable
(c) Quad copper cable
(d) Power Aluminium cable

Q6. Which layer is used to link the network support layers and user support layers?
(a) session layer
(b) transport layer
(c) data link layer
(d) network layer

Q7. Which one of the following is the impulse response of the system whose step response is given as c(t) = 0.5(1 – e^(-2t))u(t)?
(a) e^(-2t)u(t)
(b) 0.5 𝛿(t) + e^(-2t)u(t)
(c) 0.5 𝛿(t) – 0.5e^(-2t)u(t)
(d) 0.5 e^(-2t)u(t)

Q8. If P, Q and R are Boolean variables, then (P + Q’)(PQ’ + PR)(P’R’ + Q’) simplifies
(a) PQ’ + R
(b) PR’
(c) PQ’
(d) PR” + Q

Q9. The advantage of using a freewheeling diode with bridge type AC to DC converter is
(a) reliable speed control
(b) reduced cost of system
(c) regenerative braking
(d) improved input power factor

Q10. When electromagnetic waves are propagated in a waveguide
(a) They travel along the walls of the waveguide
(b) They are reflected from the walls but do not travel along the walls
(c) They travel through the dielectric without touching the walls
(d) None of the above

SOLUTIONS

S1. Ans.(b)
Sol. Program Counter is a 16-bit “Auto increment register” in which address of the next instruction to be executed is stored after the content of the current location is sent for fetch.

S2. Ans.(a)
Sol. Conversion efficiency of Class-A amplifier is
% η = (1-V_min/V_CC ) × 25%
Therefore, the maximum conversion efficiency is 25%.

S3. Ans.(c)
Sol. If f(x) is the continuous Probability Density Function of a random variable X then,
p(a < x ≤ b) = p(a ≤ x < b) = p(a ≤ x ≤ b)= ∫_a^b▒f(x)dx

S4. Ans.(b)
Sol. A Photodiode is a PN-junction diode that consumes light energy to produce electric current or voltage based on the mode of operation of the device. It is also known as photo-detector, a light detector, and photo-sensor. They mainly work in reverse bias condition. Photodiodes are used in compact disc players, smoke detectors, medical devices and the receivers for infrared remote control devices for television and AC.

S5. Ans.(d)
Sol. Except Power Aluminium cable, all others are used as communication medium between operation and operated unit.

S6. Ans.(b)
Sol. Physical, Data link and Network layers are network support layers and Session, Presentation and Application layers are user support layers. The transport layer links these layers by segmenting and rearranging the data. Protocols like TCP and UDP are used.

S7. Ans.(a)
Sol. Given:
c(t) = 0.5(1 – e^(-2t))u(t)
Impulse response is –
⇒ 𝛿(t) = (dc(t))/dt
⇒ 𝛿(t) = d/dt{0.5(1 – e^(-2t))u(t)}
⇒ 𝛿(t) =0.5(2e^(-2t))u(t)
So, 𝛿(t) = e^(-2t)u(t)

S8. Ans.(c)
Sol. (P + Q’)(PQ’ + PR)(P’R’ + Q’) = (P + Q`)P(Q` + R)(P`R` + Q`)
= (P + Q`)P(P`Q`R` + Q`Q` + P`R`R + RQ`)
= (P + Q`)P (P`Q`R` + Q` + 0 + RQ`)
= (P + Q`)(PP`Q`R` + PQ` + PRQ`) = (P + Q`)( 0 + PQ` + PRQ`)
= (P + Q`)(PQ` + PRQ’) = (P + Q`)PQ`(1 + R)
= (P + Q`)(PQ’) = PPQ` + PQ`Q`
= PQ` + PQ` = PQ’

S9. Ans.(d)
Sol: At the same firing angle, Freewheeling diode delivers more power to load as compared to without it. Volt-Ampere input is same in both the case. So, we can say that input power factor is improved due to the use of freewheeling diode.

S10. Ans.(b)
Sol. The waveguides are made up of conductor and conductor prevent travelling of waves tangential or parallel to it. Hence, the electromagnetic waves are reflected from the walls but do not travel along the walls.

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