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Logic gate circuits: Class 11 practice

AND outputs 1 only if all inputs are 1; OR outputs 1 if any input is 1; NOT inverts; NAND and NOR are NOT of AND and OR; XOR outputs 1 when inputs differ.. Read the method, follow the three worked examples, then try the six questions.

What you should know first

  • Binary digits

The idea behind logic gate circuits

AND outputs 1 only if all inputs are 1; OR outputs 1 if any input is 1; NOT inverts; NAND and NOR are NOT of AND and OR; XOR outputs 1 when inputs differ.

Step-by-step method

  1. Substitute the input bits.
  2. Evaluate inner gates first.
  3. Combine to the final output.

Worked example 1 (Basic)

A = 0, B = 0. What is A NOR B?

  1. NOR(0, 0) = 1
  2. Answer: 1

Worked example 2 (Standard)

A = 0, B = 1, C = 0. Find (A AND B) XOR C.

  1. A AND B = 0
  2. 0 XOR 0 = 0
  3. Answer: 0

Worked example 3 (Challenge)

Write the output column of Y = (A NOR B) XOR (NOT A) for AB = 00, 01, 10, 11.

  1. Evaluate each row
  2. Answer: 0, 1, 0, 0

Common mistakes and misconceptions

  • Treating XOR like OR
  • Forgetting the NOT in NAND/NOR

Practice questions

  1. (Basic) A = 0, B = 0. What is A XOR B?
  2. (Basic) A = 1, B = 1. What is A XOR B?
  3. (Standard) A = 1, B = 0, C = 0. Find (A NAND B) XOR C.
  4. (Standard) A = 1, B = 0, C = 0. Find (A NOR B) OR C.
  5. (Challenge) Write the output column of Y = (A NOR B) AND (NOT A) for AB = 00, 01, 10, 11.
  6. (Challenge) Write the output column of Y = (A NAND B) OR (NOT A) for AB = 00, 01, 10, 11.

Answer key with full working

  • Q1: XOR(0, 0) = 0 → Answer: 0
  • Q2: XOR(1, 1) = 0 → Answer: 0
  • Q3: A NAND B = 1 → 1 XOR 0 = 1 → Answer: 1
  • Q4: A NOR B = 0 → 0 OR 0 = 0 → Answer: 0
  • Q5: Evaluate each row → Answer: 1, 0, 0, 0
  • Q6: Evaluate each row → Answer: 1, 1, 1, 0

Syllabus note

This skill is listed under "Boolean Logic" for Class 11 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.

Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.

Related practice and notes

Frequently asked questions

Which chapter is logic gate circuits in?

"Boolean Logic", Class 11 Computer Science (NCERT/CBSE). Other boards may place it differently.

How were the answers checked?

Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.

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