MCQs on Logic Gates

Logic gates are devices that act as the building blocks for digital circuits, and perform basic logical functions by taking decisions through a combination of digital signals coming from the inputs. Logic gates operate on the concept of Boolean function with having two inputs and one output. There are two binary conditions, true or false where true represents 1 and false represents 0. There are different types of logic gates and based on the type of logical gate, the output varies due to variation in the logical operation. 

Multiple Choice Questions

Which gate is known as the universal gate?

1. 1. NAND
   2. OR
   3. AND
   4. None

Answer. A. NAND gate.

This is so because using multiples of nand gates, any logical gate (AND, OR, NOT, NAND,NOR) can be created. 

2. How does a logic gate function?

1. 1. Using the flow of electric current
   2. Spontaneously
   3. By using energy from a chemical reaction
   4. None of the above

Answer. A. Using the flow of electric current.

Logic gates work on the concept of getting two input electric current flows, comparing them and sending on another electrical output, depending on what it finds.

3. Which of the following is not a logic gate?

1. 1. AND
   2. OR
   3. IF
   4. NOT

Answer. C. IF is not a logic gate.

Different types of basic logic gates that are there include AND, OR, NOT. using these gates and making different combinations out of them, various other gates like NAND, NOR, etc are created but there is no such gate by the name of IF.  

4. Which of the following are the arithmetic logic gates?

1. 1. X-OR
   2. X-NOR
   3. Both
   4. None

Answer. C. Both.

X-OR and X-NOR are termed as arithmetic gates because these gates are so connected that they carry out an arithmetic action and the output they give are the digits of the result. 

5. What is the full form of DCDVS logic?

1. 1. Differential cascade voltage switch
   2. Differential cascade voltage static
   3. Differential complex voltage switch
   4. None

Answer. A. Differential cascade voltage switch is the expanded form of DCDVS logic. 

6. Who was the inventor of the idea of logic gates?

1. 1. George Boole
   2. Bardeen 
   3. Claude Shannon
   4. Kornard Zuse

Answer. A. George Boole, son of a shoemaker class family, born in Lincoln, England, was the inventor of the idea and concept of logic gates. 

7. What is the one’s complement for the binary number 011001

1. 1. 000111
   2. 100110
   3. 111001
   4. 110001

Answer. B. 100110.

The one’s complement means that one has to swap all the 0’s and 1’s. So for the given number, swapping 0’s and 1’s would give the number designated as option b as the answer. 

8. Expand TTL

1. 1. Transistor-transducer logic
   2. Transistor- transistor logic
   3. Transducer-transistor logic
   4. None

Answer. B. Transistor-transistor logic is the correct full form of TTL.

9. How many types of logic families exist?

1. 1. Two
   2. Six
   3. Four
   4. Seven

Answer. D. Seven.

There are seven types of logic families, namely, RTL, DTL, IIL, TTL, ECL, MOS, CMOS.

10. Which of the following signifies a NOT gate?

1. 1. 1 (input)- 0 (output)
   2. 1,0 (input)- 1 (output)
   3. 0,0 (input)- 0 (output)
   4. None

Answer. A. 1 (input)- 0 (output).

NOT gate reverses the input,so if input is true (1), output will be false (0) therefore, a is the correct option. 

11. What is the boolean operation performed by an OR gate?

1. 1. Equivalent of addition
   2. Equivalent of multiplication
   3. Equivalent of dificsin
   4. Equivalent of subtraction. 

Answer. A. Equivalent of addition

An OR gate performs addition function, so that if any of the two inputs is 1, it will give the output also as 1. 

12. Which of the following gates can function on a single input?

1. 1. NOT
   2. AND
   3. OR
   4. None

Answer.A. Not gate can function on a single input, and invert that input. 

13. A NAND gate has —– inputs and —— outputs. 

1. 1. High input and High output
   2. High input and low output
   3. Low input and low output
   4. Low input and high output

Answer. D. Low input and high output.

A NAND gate is a combination of NOT and AND gates, so it will convert two low inputs to high inputs first and then give an AND based output for the modified inputs. 

14. What is the Truth Table?

1. 1. It is a table representing what output will one get for a given input. 
   2. It is a table representing what input and output will be given by a given boolean operator. 
   3. Both of these
   4. None of these

Answer. C. Both of these.

Truth table represents for a given logic gate, what output will a particular input give. 

15. What will be the output of the given logic gate?

1. NOR
2. NAND
3. AND
4. OR

Answer. 2.NAND gate.

These are a combination of OR gates and thus will in totality function to first invert the input and then give the high value output.

16. What is the full form of ILL?

1. 1. Injection integrated circuit
   2. Integrated injection circuit
   3. Integrated integrated circuit
   4. None 

Answer. B. Integrated Injection circuit.

17. Who first made use of truth tables?

1. 1. Charles Sanders Pierce
   2. Father of Pragmatism
   3. Irving Annelis
   4. Both a and b

Answer. D. Both a and b.

Charles Sanders Pierce is also called the father of pragmatism, who first made use of truth tables. 

18. Which are the forms of complex logic gates?

1. 1. OAI
   2. AOI
   3. Both 
   4. None

Answer. C. Both OAI (OR-AND- Invert) and AOI (AND-OR-Invert) are the forms of complex logic gates. 

19. What combination is a NAND gate?

1. 1. NOT AND 
   2. NOT OR
   3. NOT NOT
   4. None of these

Answer. A. NOT AND.

NAND is a combination of NOT + AND gates

20.  XOR circuits can be constructed using

1. 1. OR gates only
   2. AND, OR gates
   3. AND, NOT gates
   4. AND, NOT and OR gates

Answer. D. AND, NOT and OR gates can be combined to get exclusive-OR gates.