# ELECTRICAL ENGINEERING IMPORTANT MCQ-DIGITAL ELECTRONICS

1.In which of the following base systems is 123 not a valid number?

(a) Base 10

(b) Base 16

(c)Base8

(d) Base 3

Ans:d

2. Storage of 1 KB means the following number of bytes

(a) 1000

(b)964

(c)1024

(d) 1064

Ans:c

3. What is the octal equivalent of the binary number:

10111101

(a)675

(b)275

(c) 572

(d) 573.

Ans:b

4. Pick out the CORRECT statement:

(a) In a positional number system, each symbol represents the same value irrespective of its position

(b) The highest symbol in a position number system as a value equal to the number of symbols in the system

(c) It is not always possible to find the exact binary

(d) Each hexadecimal digit can be represented as a sequence of three binary symbols.

Ans:c

5.The binary code of (21.125)10 is

(a) 10101.001

(b) 10100.001

(c) 10101.010

(d) 10100.111.

Ans:a

6.A NAND gate is called a universal logic element because

(a) it is used by everybody

(b) any logic function can be realized by NAND gates alone

(c) all the minization techniques are applicable for optimum NAND gate realization

(d) many digital computers use NAND gates.

Ans:b

7. Digital computers are more widely used as compared to analog computers, because they are

(a) less expensive

(b) always more accurate and faster

(c) useful over wider ranges of problem types

(d) easier to maintain.

Ans:c

8. Most of the digital computers do not have floating point hardware because

(a) floating point hardware is costly

(b) it is slower than software

(c) it is not possible to perform floating point addition by hardware

(d) of no specific reason.

Ans:a

9. The number 1000 would appear just immediately after

(a) FFFF (hex)

(b) 1111 (binary)

(c) 7777 (octal)

(d) All of the above.

Ans:d

10. (1(10101)2 is

(a) (37)10

(b) ( 69)10

(c) (41 )10

(d) — (5)10

Ans:a

11. The number of Boolean functions that can be generated by n variables is equal to

(a) 2n

(b) 22 n

(c) 2n-1

(d) — 2n

Ans:b

12. Consider the representation of six-bit numbers by two’s complement, one’s complement, or by sign and magnitude: In which representation is there overflow from the addition of the integers 011000 and 011000?

(a) Two’s complement only

(b) Sign and magnitude and one’s complement only

(c) Two’s complement and one’s complement only

(d) All three representations.

Ans:d

13. A hexadecimal odometer displays F 52 F. The next reading will be

(a)F52E

(b)G52F

(c)F53F

(d)F53O.

Ans:d

14. Positive logic in a logic circuit is one in which

(a) logic 0 and 1 are represented by 0 and positive voltage respectively

(b) logic 0 and, -1 are represented by negative and positive voltages respectively

(c) logic 0 voltage level is higher than logic 1 voltage level

(d) logic 0 voltage level is lower than logic 1 voltage level.

Ans:d

15. Which of the following gate is a two-level logic gate

(a) OR gate

(b) NAND gate

(c) EXCLUSIVE OR gate

(d) NOT gate.

Ans:c

16. Among the logic families, the family which can be used at very high frequency greater than 100 MHz in a 4 bit

synchronous counter is

(a) TTLAS

(b) CMOS

(c)ECL

(d)TTLLS

Ans:c

17. An AND gate will function as OR if

(a) all the inputs to the gates are “1”

(b) all the inputs are ‘0’

(c) either of the inputs is “1”

(d) all the inputs and outputs are complemented.

Ans:d

18. An OR gate has 6 inputs. The number of input words in its truth table are

(a)6

(b)32

(c) 64

(d) 128

Ans:c

19. A debouncing circuit is

(a) an astable MV

(b) a bistable MV

(c) a latch

(d) a monostable MV.

Ans:c

20. NAND. gates are preferred over others because these

(a) have lower fabrication area

(b) can be used to make any gate

(c) consume least electronic power

(d) provide maximum density in a chip.

Ans:b

21. In case of OR gate, no matter what the number of inputs, a

(a) 1 at any input causes the output to be at logic 1

(b) 1 at any input causes the output to be at logic 0

(c) 0 any input causes the output to be at logic 0

(d) 0 at any input causes the output to be at logic 1.

Ans:a

22. The fan put of a 7400 NAND gate is

(a)2TTL

(b)5TTL

(c)8TTL

(d)10TTL

Ans:d

23. Excess-3 code is known as

(a) Weighted code

(b) Cyclic redundancy code

(c) Self-complementing code

(d) Algebraic code.

Ans:c

24. Assuming 8 bits for data, 1 bit for parity, I start bit and 2 stop bits, the number of characters that 1200 BPS communication line can transmit is

(a)10 CPS

(b)120 CPS

(c) 12CPS

(d) None of the above.

Ans:c

25. Indicate which of the following three binary additions are correct?

1.1011 + 1010 = 10101

II. 1010 + 1101 = 10111

III. 1010 + 1101 = 11111

(a) I and II

(b) II and III

(c) III only

(d) II and III

Ans:a

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