Quiz Electronics Engineering 1 Aug 2020

Quiz Electronics Engineering
Exam: NIC
Topic: Miscellaneous
Date: 01/08/2020

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

Q1. The ideal Op-Amp has the following characteristics:
(a) R_i = ∞, A = ∞, R_o = 0
(b) R_i = 0, A = ∞, R_o = 0
(c) R_i = ∞, A = ∞, R_o = ∞
(d) R_i = 0, A = ∞, R_o = ∞

Q2. A 3 µF capacitor is charged by a constant current of 2 µA for 6 seconds. The voltage across the capacitor to the end of charging will be
(a) 9 V
(b) 6 V
(c) 4 V
(d) 3 V

Q3. Gunn diode is a:
(a) Negative resistance device
(b) Positive resistance device
(c) High noise device
(d) Low frequency device

Q4. The number of nibbles which make up one byte is …..
(a) 2
(b) 4
(c) 8
(d) 16

Q5. The input and output of a continuous time system are respectively denoted by x(t) and y(t). Which of the following descriptions corresponds to a causal system?
(a) y(t) = x(t-2) + x(t+4)
(b) y(t) = (t-4)x(t+1)
(c) y(t) = (t+5)x(t+5)
(d) y(t) = (t+4)x(t-1)

Q6. The VHF band is
(a) 30 Hz – 300 Hz
(b) 300 Hz – 3 KHz
(c) 3 MHz – 30 MHz
(d) 30 MHz – 300 MHz

Q7. In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be
(a) 1655 kHz
(b) 745 kHz
(c) 2110 kHz
(d) 910 kHz

Q8. Resistance of a conductor is proportional to its
(a) length
(b) width
(c) both (a) and (b)
(d) none of these

Q9. A DIAC can be fired
(a) only by +ve half cycle of supply
(b) only by –ve half cycle of supply
(c) both (a) and (b)
(d) without any biasing

Q10. Programs in which of the following memories can’t be erased ?
(a) RAM
(b) ROM
(c) Cache Memory
(d) Virtual Memory

SOLUTIONS

S1. Ans. (a)
Sol. In an Ideal Operational Amplifier input resistance is infinite, output resistance is always zero and Gain is also infinity.
So, R_i = ∞, A = ∞, R_o = 0 is the correct option.

S2. Ans.(c)
Sol. Given:
C = 3 µF = 3 × 10^(-6) F
I = 2 µA = 2 × 10^(-6) A
time = t = 6 sec
We know that,
I = CdV/dt
At the end of charging,
⇒ V = (I × t)/C
⇒ V = (2 × 10^(-6) × 6)/(3 × 10^(-6) )
⇒ V = (2 × 6)/3
So, V = 4 V

S3. Ans.(a)
Sol. A Gunn diode is a two-terminal semiconductor diode, with Negative Differential Resistance. It is also known as a transferred electron device (TED). It is based on the “Gunn effect” Gunn diodes are used to build oscillators for generating microwaves with high frequencies ranging from GHz to THz. It is a tuned circuit consisting of Gunn diode with DC bias voltage applied to it.

S4. Ans.(a)
Sol. The number of nibbles which make up one byte is 2 because we know that
⇒ 1 nibble = 4 bit
and 1 byte = 8 bits
So, 1 byte = 2 nibbles

S5. Ans.(d)
Sol. A system is said to be causal if the output at any time depends only on the present and the past values. i.e. for t < 0, y(t) = 0.

S6. Ans.(d)

S7. Ans.(c)
Sol. Given:
IF frequency(fIF) = 455 kHz
Tuned frequency(fS) = 1200 kHz
We know that, Image frequency is
⇒ fS = fS + 2fIF
So, fSi = 1200 + 2 x 455 = 1200 + 910 = 2110 kHz

S8. Ans.(a)
Sol. Resistance of a conductor is
R=ρ l/a
where,
ρ = specific resistivity
l = length of the conductor
A = cross-sectional area.

S9. Ans.(c)
Sol. DIAC are three terminal bidirectional device. So, if a DIAC can be fired in +ve half cycle of supply then it can also be fired in –ve half cycle when it is connected in reversed direction into the circuit.

S10. Ans.(b)
Sol.
ROM (Read Only Memory) is a non-volatile memory because the data stored in ROM is not lost or erased when the computer power is turned off.
Virtual memory is a memory management capability of an operating system. In this data is temporarily transferred from Random Access Memory (RAM) to disk storage using hardware and software. It is used to compensate for physical memory shortages.
A Cache memory is a small and very fast temporary storage memory. It is designed to speed up the transfer of data and instructions by storing program instructions that are frequently re-referenced by software during operation. It is located inside or close to the CPU chip. It is faster than RAM.

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