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Boolean logic and logic gates

Lesson details

Learning outcome

I can identify different logic gates and construct the truth table for each logic gate.

Key learning points

  1. Boolean logic is a form of algebra where all logical relations can be expressed as a combination of AND, OR and NOT.
  2. A logic gate is a fundamental component of a digital circuit.
  3. Each logic gate has a symbol, which is used in circuit diagrams.
  4. Each logic gate has a unique truth table that shows how the output changes with different inputs.

Keywords

  • Boolean - an expression that evaluates to either True or False

  • Logic gate - an electronic component that carries out a logical operation

  • Truth table - a table showing the outputs for all possible combinations of inputs to a logic gate or logic circuit

Common misconception

All logic gates have two inputs and one output.

The number of inputs depends on the logic gate. The NOT gate is different in that it only has one input.

Teacher tip

Get students into the practice of writing out the possible inputs for a truth table as if they were counting in binary. For the AND and OR gates this is 00, 01, 10, 11.

Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0
except where otherwise stated. See Oak's terms & conditions
(Collection 2).

Lesson video

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Prior knowledge starter quiz

6 Questions

Q1.
What are the binary digits?

Correct answer: 1
Correct answer: 0
True
8

Q2.
What do logical operations operate on?

Correct answer: statements that are either True or False
binary circuits
numbers
hardware components

Q3.
What is the result of the statement "NOT raining" when it is raining?

True
Correct answer: False

Q4.
What do binary digits represent in hardware logic?

Correct answer: True or False values
electrical noise in the circuit
unprocessed data

Q5.
A Boolean logic system in computers processes data using 1s and 0s, which represent high and voltages.

Correct Answer: low

Q6.
Logic gates are physical components used in computers to carry out operations.

Correct answer: logical
arithmetic
graphical

6 Questions

Q1.
Who introduced Boolean logic?

Correct answer: George Boole
Claude Shannon
Charles Babbage
Alan Turing

Q2.
What does a Boolean expression evaluate to?

Correct answer: True or False
a numerical value
a text message

Q3.
Which of the following is an example of a Boolean statement?

Correct answer: The sky is blue.
Please open the window.
What is your favourite film?
How old are you?

Q4.
Which logic gate has only one input and one output?

Correct answer: NOT
AND
OR

Q5.
What is the output of an AND gate when both inputs are 1?

Correct Answer: 1, True

Q6.
How many possible input combinations exist for an AND gate with two inputs?

Correct answer: 4
1
2
8

To help you plan your 10 computer science lesson on: Boolean logic and logic gates, download all teaching resources for free and adapt to suit your pupils' needs...