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Syllabus

NEC Electronics · Practice

Chapters & sets

1. Basic Electrical and Electronics Engineering

Basic Electrical

Set 1106

Basic Electronics

Set 171 Set 233

2. Digital Logic and Microprocessor

Digital Logic

Set 150 Set 250 Set 350 Set 450 Set 550 Set 650 Set 749 Set 851 Set 950 Set 1050 Set 1150 Set 1232

Microprocessor

Set 150 Set 250 Set 350 Set 445 Set 550 Set 650 Set 720 Set 850 Set 969

3. Programming Language and Its Applications

Mixed chapter MCQs

Set 150 Set 249 Set 349 Set 451 Set 540

4. Computer Organization and Embedded Systems

Mixed chapter MCQs

Set 150 Set 249 Set 350 Set 450 Set 550 Set 650 Set 750 Set 849 Set 950 Set 1050 Set 1150

5. Computer Networks and Network Security

Basic Networking

Set 150 Set 253

Advanced Networking

Set 150 Set 250 Set 350 Set 450 Set 550 Set 655

10. Project Planning, Design and Implementation

Digital Logic Set 7

49 questions

Question 1

The output of an SR flip-flop when

S = 1

and

R = 0

is:

A.
$1$

B.

\text{No change}

C.

0

D.

\text{High impedance}

Question 2

The number of flip-flops contained in IC 7490 is:

A.
$2$
B.
$4$
C.
$3$
D.
$10$

Question 3

The number of control lines for a 32-to-1 multiplexer is:

A.
$4$
B.
$16$
C.
$5$
D.
$6$

Question 4

How many two-input AND & OR gates are required to realize

Y = CD + EF + G

?

A.
$2, 2$
B.
$3, 3$
C.
$2, 3$
D.
$\text{None of these}$

Question 5

Which of the following cannot be accessed randomly?

A.
$\text{DRAM}$
B.
$\text{ROM}$
C.
$\text{SRAM}$
D.
$\text{Magnetic tape}$

Question 6

The excess-3 code of decimal 7 is represented by:

A.
$1100$
B.
$1011$
C.
$1001$
D.
$1010$

Question 7

When an input signal

A = 11001

is applied to a NOT gate serially, its output signal is:

A.
$00111$
B.
$10101$
C.
$00110$
D.
$11001$

Question 8

The result of adding the hexadecimal number A6 to 3A is:

A.
$DD$
B.
$F0$
C.
$E0$
D.
$EF$

Question 9

A universal logic gate is one that can be used to generate any logic function. Which of the following is a universal logic gate?

A.
$\text{OR}$
B.
$\text{XOR}$
C.
$\text{AND}$
D.
$\text{NAND}$

Question 10

The logic 0 level of a CMOS logic device is approximately:

A.
$1.2 \text{ volts}$
B.
$5 \text{ volts}$
C.
$0.4 \text{ volts}$
D.
$0 \text{ volts}$

Question 11

A Karnaugh map is used for the purpose of:

A.
$\text{Reducing the electronic circuits used}$
B.
$\text{Mapping the given Boolean logic function}$
C.
$\text{Minimizing the terms in a Boolean expression}$
D.
$\text{Maximizing the terms of a given Boolean expression}$

Question 12

A full adder logic circuit will have:

A.
$\text{Two inputs and one output}$
B.
$\text{Three inputs and three outputs}$
C.
$\text{Two inputs and two outputs}$
D.
$\text{Three inputs and two outputs}$

Question 13

An eight-stage ripple counter uses flip-flops with a propagation delay of 75 nanoseconds each. The pulse width of the strobe is 50 ns. The frequency of the input signal which can be used for proper operation of the counter is approximately:

A.
$1 \text{ MHz}$
B.
$2 \text{ MHz}$
C.
$500 \text{ MHz}$
D.
$4 \text{ MHz}$

Question 14

The output of a JK flip-flop with asynchronous preset and clear inputs is '1'. The output can be changed to '0' with one of the following conditions:

A.
$\text{By applying } J = 0, K = 0 \text{ and using a clock}$
B.
$\text{By applying } J = 1, K = 0 \text{ and using the clock}$
C.
$\text{By applying } J = 1, K = 1 \text{ and using the clock}$
D.
$\text{By applying a synchronous preset input}$

Question 15

The information in ROM is stored:

A.
$\text{By the user any number of times}$
B.
$\text{By the manufacturer during fabrication of the device}$
C.
$\text{By the user using ultraviolet light}$
D.
$\text{By the user once and only once}$

Question 16

The conversion speed of an analog-to-digital converter is maximum with the following technique:

A.
$\text{Dual slope A/D converter}$
B.
$\text{Serial comparator A/D converter}$
C.
$\text{Successive approximation A/D converter}$
D.
$\text{Parallel comparator A/D converter}$

Question 17

A weighted resistor digital-to-analog converter using N bits requires a total of:

A.
$N \text{ precision resistors}$
B.
$N + 1 \text{ precision resistors}$
C.
$2N \text{ precision resistors}$
D.
$N - 1 \text{ precision resistors}$

Question 18

The 2's complement of the number 1101110 is:

A.
$0010001$
B.
$0010010$
C.
$0010001$
D.
$\text{None}$

Question 19

The decimal equivalent of the binary number 10101 is:

A.
$21$
B.
$26$
C.
$31$
D.
$28$

Question 20

How many two-input AND gates and two-input OR gates are required to realize

Y = BD + CE + AB

?

A.
$1, 1$
B.
$3, 2$
C.
$4, 2$
D.
$2, 3$

Question 21

How many select lines will a 32-to-1 multiplexer have?

A.
$5$
B.
$9$
C.
$8$
D.
$11$

Question 22

How many address bits are required to represent 4K memory?

A.
$5 \text{ bits}$
B.
$8 \text{ bits}$
C.
$12 \text{ bits}$
D.
$10 \text{ bits}$

Question 23

For a JK flip-flop with

J = 0

and

K = 1

, the output after a clock pulse will be:

A.
$1$
B.
$0$
C.
$\text{No change}$
D.
$\text{High impedance}$

Question 24

Which of the following are known as universal gates?

A.
$\text{NAND and NOR}$
B.
$\text{XOR and OR}$
C.
$\text{AND and OR}$
D.
$\text{None}$

Question 25

Which of the following memories stores the most number of bits?

A.
$\text{64Kx8 memory}$
B.
$\text{32Mx8 memory}$
C.
$\text{1Mx8 memory}$
D.
$\text{64x6 memory}$

Question 26

Which of the following consumes minimum power?

A.
$\text{TTL}$
B.
$\text{DTL}$
C.
$\text{CMOS}$
D.
$\text{RTL}$

Question 27

The complement of a variable is always:

A.
$0$
B.
$\text{Equal to the variable}$
C.
$1$
D.
$\text{The inverse of the variable}$

Question 28

The Boolean expression

A + B + C

is:

A.
$\text{A sum term}$
B.
$\text{A product term}$
C.
$\text{A literal term}$
D.
$\text{A complement term}$

Question 29

The Boolean expression

AB'CD'

is:

A.
$\text{A sum term}$
B.
$\text{A literal}$
C.
$\text{A product term}$
D.
$\text{Always 1}$

Question 30

The domain of the expression

AB'CD + AB' + C'D + B

is:

A.
$A \text{ and } D$
B.
$A, B, C, \text{ and } D$
C.
$B \text{ only}$

Question 31

According to the commutative law of addition:

A.
$AB = BA$
B.
$A + (B + C) = (A + B) + C$
C.
$A = A + A$
D.
$A + B = B + A$

Question 32

According to the associative law of multiplication:

A.
$B = BB$
B.
$A + B = B + A$
C.
$A(BC) = (AB)C$
D.
$B + B(B + 0)$

Question 33

According to the distributive law:

A.
$A(B + C) = AB + AC$
B.
$A(A + 1) = A$
C.
$A(BC) = (AB)C$
D.
$A + AB = A$

Question 34

Which one of the following is not a valid rule of Boolean algebra?

A.
$A + 1 = 1$
B.
$AA = A$
C.
$A = A$
D.
$A + 0 = A$

Question 35

Which of the following rules states that if one input of an AND gate is always 1, the output is equal to the other input?

A.
$A + 1 = 1$
B.
$AA = A$
C.
$A + A = A$
D.
$A \cdot 1 = A$

Question 36

According to De Morgan’s theorems, the following equality(s) are correct:

A.
$\overline{AB} = \overline{A} + \overline{B}$
B.
$\overline{A + B + C} = \overline{A} \cdot \overline{B} \cdot \overline{C}$
C.
$\overline{XYZ} = \overline{X} + \overline{Y} + \overline{Z}$
D.
$\text{All of the above}$

Question 37

The Boolean expression

X = AB + CD

represents:

A.
$\text{Two ORs ANDed together}$
B.
$\text{Two ANDs ORed together}$
C.
$\text{A 4-input AND gate}$
D.
$\text{An exclusive-OR}$

Question 38

An example of a sum-of-products expression is:

A.
$A + B(C + D)$
B.
$AB + AC + ABC$
C.
$(A + B + C)(A + B + C)$
D.
$\text{Both answers A and B}$

Question 39

An example of a sum-of-sums expression is:

A.
$A(B + C) + AG$
B.
$A + B + BC$
C.
$(A + B)(A + B + C)$
D.
$\text{Both answers A and B}$

Question 40

An example of a standard SOP expression is:

A.
$AB + ABC + ABD$
B.
$AB + AB + AB$
C.
$ABC + ACD$
D.
$ABCD + AB + A$

Question 41

A 3-variable Karnaugh map has:

A.
$\text{Eight cells}$
B.
$\text{Sixteen cells}$
C.
$\text{Three cells}$
D.
$\text{Four cells}$

Question 42

In a 4-variable Karnaugh map, a 2-variable product term is produced by:

A.
$\text{A 2-cell group of 1s}$
B.
$\text{A 4-cell group of 1s}$
C.
$\text{An 8-cell group of 1s}$
D.
$\text{A 4-cell group of 0s}$

Question 43

On a Karnaugh map, grouping the 0s produces:

A.
$\text{A product-of-sums expression}$
B.
$\text{A "don’t care" condition}$
C.
$\text{A sum-of-products expression}$
D.
$\text{AND-OR logic}$

Question 44

A 5-variable Karnaugh map has:

A.
$\text{Sixteen cells}$
B.
$\text{Sixty-four cells}$
C.
$\text{Thirty-two cells}$
D.
$\text{All of the above}$

Question 45

The output expression for an AND-OR circuit having one AND gate with inputs

A, B, C, D

and one AND gate with inputs

E, F

is:

A.
$ABCDEF$
B.
$(A + B + C + D)(E + F)$
C.
$AFE + C + D + E + F$
D.
$BCD + EF$

Question 46

A logic circuit with an output

X = ABC + AC

consists of:

A.
$\text{Two AND gates and one OR gate}$
B.
$\text{Two AND gates, one OR gate, and two inverters}$
C.
$\text{Two OR gates, one AND gate, and two inverters}$
D.
$\text{Two AND gates, one OR gate, and one inverter}$

Question 47

To implement the expression

ABCD + ABCD + ABCD

, it takes one OR gate and:

A.
$\text{One AND gate}$
B.
$\text{Three AND gates and four inverters}$
C.
$\text{Three AND gates}$
D.
$\text{Three AND gates and three inverters}$

Question 48

The expression

ABCD + ABCD + ABCD

:

A.
$\text{Cannot be simplified}$
B.
$\text{Can be simplified to } ABCD + ABC$
C.
$\text{Can be simplified to } ABC + AB$
D.
$\text{None of these answers is correct}$

Question 49

The input expression for an AND-OR-Invert circuit having one AND gate with inputs

A, B, C, D

and one AND gate with inputs

E, F

is:

A.
$ABCD + EF$
B.
$A + B + C + D + E + F$
C.
$(A + B + C + D)(E + F)$
D.
$(A + B + C + D)(E + F)$

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D.

\text{None of the above}