Quiz Electronics Engineering 10 Oct 2020

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

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

Q1. A FET can be used as a variable
(a) inductor
(b) capacitor
(c) resistor
(d) voltage source

Q2. In a weighted-resistor digital-to-analog converter with 8-bit input, if the resistance corresponding to the MSB is 2kΩ, what will be the resistance corresponding to the LSB?
(a) 250 kΩ
(b) 256 kΩ
(c) 512 kΩ
(d) 25.5 kΩ

Q3. The impulse response of a system is h(t) = 𝛿(t – 0.5). If two such systems are cascaded, the impulse response of the overall system will be
(a) 𝛿(t – 1)
(b) 𝛿(t – 0.25)
(c) 0.5𝛿(t – 0.25)
(d) 0.5𝛿(t – 1)

Q4. A 1 μF capacitor is connected to 12 V battery. The energy stored in the capacitor is:
(a) 12×10^(-6) J
(b) 24×10^(-6) J
(c) 48×10^(-6) J
(d) 72×10^(-6) J

Q5. Thyristor is a semiconductor switch which is
(a) unilateral and astable
(b) bilateral and bistable
(c) unilateral and bistable
(d) bilateral and astable

Q6. Personal computer’s Basic Input Output System(BIOS) is present in –
(a) RAM chips
(b) magnetic tapes
(c) registers
(d) ROM chips

Q7. De-emphasis circuit is used
(a) before detection
(b) after detection
(c) before modulation
(d) after modulation

Q8. The property of Fourier Transform which states that the compression in time domain is equivalent to expansion in the frequency domain is
(a) duality
(b) frequency shifting
(c) scaling
(d) time scaling

Q9. If the potential functions V_1 and V_2 satisfy Laplace’s equation with in a closed region and assume the same values on its surface, then which of the following is correct?
(a) V_1 and V_2 are identical.
(b) V_1 is inversely proportional to V_2 .
(c) V_1 has the same direction as V_2.
(d) V_1 has the same magnitude as V_2 but has different direction.

Q10. Which of the following is a MAC address?
(b) 00056A:01A01A:5CCA7F:F60
(c) 01 : A5 : BB : A7: FF : 60
(d) 568


S1. Ans. (c)
Sol. Small Signal FET drain resistance varies with applied gate-source voltage V_GS and so FET acts like a Voltage Variable Resistor.

S2. Ans.(b)
Sol. Given:
Resistance corresponding to the MSB = 2kΩ
Number of bits(n) = 8
We know that, Resistance corresponding to LSB is
⇒ R_LSB = 2 × 2^(8-1)
⇒ R_LSB = 2^8 kΩ
So, R_LSB = 256 kΩ

S3. Ans.(a)
Sol. According to the property of Impulse response –
𝛿(t – a)* 𝛿(t – b) = 𝛿(t – a – b)
Here, When the system is cascaded, the overall impulse response is –
⇒ 𝛿(t – 0.5)* 𝛿(t – 0.5) = 𝛿(t – 0.5 – 0.5)
So, 𝛿(t – 0.5)* 𝛿(t – 0.5) = 𝛿(t – 1)

S4. Ans. (d)
Sol. Given:
V = 12 volts
C = 1 μF = 10^(-6) F
We know that Energy stored in the capacitor is
⇒ W =1/2 CV^2
⇒ W = 1/2 × 12^2 × 10^(-6) J
⇒ W = 1/2 × 144 × 10^(-6) J
So, W = 72 × 10^(-6) J

S5. Ans.(c)
Sol. A thyristor is a solid-state semiconductor device having four layers. P- and N-type materials are arranged alternately. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed (by some other means). Thyristor also called SCR is a unidirectional device i.e. Unilateral. It has three modes of operation. Those are-
1. Forward conduction mode
2. Forward blocking mode
3. Reverse blocking mode
First two are stable states so, it is called Bistable.

S6. Ans.(d)
Sol. BIOS is present in the ROM chip of Personal Computer. It is a firmware which initialize the booting process when the system is turned ON.

S7. Ans (b)
Sol. De-emphasis means attenuating those frequencies by the amount by which they are boosted. It will be done in the receiver side after demodulation i.e., after detection.

S8. Ans.(d)
Sol. In Time Scaling,
x(at) ↔┴( F.T ) 1/|a| X(f/a)

S9. Ans.(a)

S10. Ans.(c)
Sol. The standard format of MAC contains 48 bits. Each 4 bits is represented in hexadecimal format i.e. 12 hexadecimal numbers in group, each contains 2 hexadecimal number and each separated by : or – or ;
So, 01 : A5 : BB : A7 : FF : 60 is a MAC address.

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