# Logic Gate MCQ

## Logic Gate MCQ

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Combinational Circuit MCQ

### Multiple Choice Questions

Q.1. What logic function is produced by adding inverters to the inputs of an OR gate?

• NOR
• NAND
• AND
• X-NOR

Q.2. What logic function is produced by adding an inverter to each input and output of an AND gate?

• NOR
• NAND
• X-OR
• OR

Q.3. What logic function is produced by adding an inverter to each input and output of an OR gate?

• NAND
• NOR
• AND
• X-OR

Q.4. Which of the following gates is known as a coincidence detector?

• AND gate
• NAND gate
• X-OR
• X-NOR gate

Q.5. Which of the following gates is known as anticoincidence detector?

• OR gate
• X-OR gate
• AND gate
• X-NOR gate

Q.6. The output of a NOR gate is high

• only when all the inputs are low
• only when all the inputs are high
• only when at least one input is high
• only when at least one input is low

Answer: only when all the inputs are low

Q.7. The output of a NAND gate is low

• only when all the inputs are low
• only when all the inputs are high
• only when at least one input is high
• only when at least one input is low

Answer: only when all the inputs are high

Q.8. How many NOR gates are required to obtain AND operation?

• 2
• 3
• 4
• 1

Q.9. What is the minimum number of NAND gates required to realize an X-OR gate?

• 3
• 4
• 5
• 6

Q.10. What is the minimum number of NOR gates required to realize an X-OR gate?

• 3
• 4
• 5
• 6

Q.11. An AND gate can be imagined as

• switches connected in series
• switches connected in parallel
• transistors connected in series
• transistors connected in parallel

Answer: switches connected in series

Q.12. An OR gate can be imagined as

• switches connected in series
• switches connected in parallel
• transistors connected in series
• transistors connected in parallel

Answer: switches connected in parallel

Q.13. An all or nothing gate is the other name of

• AND gate
• OR gate
• X-OR gate
• X-NOR gate

Q.14. An any or all gate is the other name of

• AND gate
• OR gate
• X-OR gate
• X-NOR gate

Q.15. A bubbled AND gate is equivalent to a

• OR gate
• NAND gate
• NOR gate
• X-OR gate

Q.16. A bubbled OR gate is equivalent to a

• AND gate
• NAND gate
• NOR gate
• X-OR gate

Q.17. A bubbled NAND gate is equivalent to

• OR gate
• NAND gate
• NOR gate
• X-OR gate

Q.18. A bubbled NOR gate is equivalent to a

• AND gate
• NAND gate
• NOR gate
• X-OR gate

Q.19. The output of a gate is LOW when at least one of its inputs is HIGH. This is true for

• AND
• NAND
• NOR
• OR

Q.20. The output of a gate is HIGH when at least one of its inputs is LOW. It is true for

• X-OR
• NAND
• NOR
• OR

Q.21. The output of a gate is LOW if and only if all its inputs are HIGH. It is true for

• AND
• X-NOR
• NOR
• NAND

Q.22. The output of a gate is HIGH if and only if all its inputs are LOW. It is true for

• NOR
• X-OR
• NAND
• X-NOR

Q.23. The most suitable gate for comparing two bits is

• AND
• OR
• NAND
• X-OR

Q.24. Which of the following gates cannot be used as an inverter?

• NAND
• AND
• NOR
• X-NOR

Q.25. A gate is enabled when its enable input is at logic 1. The gate is

• OR
• NAND
• NOR
• none of these

Q.26. A gate is enabled when its enable input is at logic 0. The gate is

• NOR
• AND
• NAND
• none of these

Q.27. A gate is inhibited when its inhibit input is at logic 1. The gate is

• AND
• NAND
• OR
• none of these

Q.28. A gate is disabled when its disable input is at logic 0. The gate is

• AND
• NOR
• OR
• None of these

Q.29. The output of a logic gate is 1 when all its inputs are at logic 1. The gate is either

• a NAND or a NOR
• an AND or an OR
• an OR or an X-OR
• an AND or a NOR

Answer: an AND or an OR

Q.30. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either

• a NAND or a NOR
• an AND or an X-NOR
• an OR or a NAND
• an X-OR or an X-NOR

Answer: a NAND or a NOR

Q.31. The output of a logic gate is 1 when all its inputs are at logic 1. The gate is either

• an OR or an X-OR
• a NAND or an X-NOR
• an AND or a NAND
• an OR or an X-NOR

Answer: an OR or an X-NOR

Q.32. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either

• a NOR or an X-NOR
• a NAND or an X-OR
• an OR or an X-NOR
• an AND or an X-OR

Answer: a NOR or an X-NOR

Q.33. The output of a logic gate is 0 when all its inputs are at logic 1. The gate is either

• a NAND or an AND
• a NAND or an X-OR
• a NOR or an X-NOR
• a NAND or an X-NOR

Answer: a NAND or an AND

Q.34. The output of a logic gate is 0 when all its inputs are at logic 0. The gate is either

• an AND or a NOR
• a NAND or an X-OR
• an OR or an X-OR
• an OR or an X-NOR

Answer: an OR or an X-OR

Q.35. The number of rows in the truth table of a 4-input gate is

• 4
• 8
• 12
• 16