Boolean Logic Exam Practice (OCR J277 Paper 2 Style)

This lesson brings together everything from the Boolean Logic topic and provides exam-style practice for OCR J277 Paper 2 (Computational Thinking, Algorithms and Programming). Boolean logic questions appear in Paper 2 and can range from 1-mark recall questions to 6-mark extended response questions.

---

What to Expect in the Exam

Boolean logic questions in OCR J277 Paper 2 may ask you to:

Question type	Typical marks	What you need to do
Identify a gate from a truth table	1-2	Name the gate that matches the given truth table
Complete a truth table	2-4	Fill in missing output values for a given circuit
Draw a logic circuit	2-3	Draw the gates for a given Boolean expression
Write a Boolean expression	2-3	Convert a circuit diagram or truth table to an expression
Trace through a circuit	3-4	Calculate the output for given inputs
Simplify an expression	2-3	Use Boolean algebra rules to simplify
Apply De Morgan's Laws	2-3	Rewrite an expression using De Morgan's Laws

---

Practice Question 1: Gate Identification (1 mark)

A logic gate has the following truth table:

A	B	Q
0	0	1
0	1	0
1	0	0
1	1	0

State the name of this logic gate.

Answer: NOR gate

Explanation: The output is 1 only when both inputs are 0. This is the inverse of OR (which outputs 0 only when both inputs are 0).

---

Practice Question 2: Truth Table Completion (3 marks)

Complete the truth table for the circuit: Q = (A AND B) OR (NOT C)

A	B	C	A AND B	NOT C	Q
0	0	0	0	1	1
0	0	1	0	0	0
0	1	0	0	1	1
0	1	1	0	0	0
1	0	0	0	1	1
1	0	1	0	0	0
1	1	0	1	1	1
1	1	1	1	0	1

OCR Exam Tip: Always include intermediate columns in your truth table working, even if the question does not explicitly ask for them. This shows your method and helps you avoid errors.

---

Practice Question 3: Writing a Boolean Expression (2 marks)

Write the Boolean expression for a circuit where gate 1 is an AND gate with inputs A and B, and gate 2 is an OR gate with inputs from gate 1 and input C.

Answer: Q = (A AND B) OR C

---

Practice Question 4: Circuit Tracing (3 marks)

A circuit implements the expression: Q = NOT(A OR B) AND C

Calculate the output Q when A = 0, B = 1, C = 1.