SS 2 First Term

Lesson objectives

By the end of the week, learners should be able to:

1. Define AND, OR and NOT gates and state the operation of each.
2. Complete truth tables for each gate and each compound expression.
3. Simplify a Boolean expression using De Morgan's laws.
4. Draw simple gate circuits on paper.
5. State why combinational circuits produce predictable outputs.

Key vocabulary

• Logic gate: a circuit performing a fundamental boolean operation.
• AND gate: produces one output only when all inputs are true.
• OR gate: produces output when any input is true.
• NOT gate: inverts its single input.
• Truth table: a table listing outputs for every input combination.
• Boolean expression: a formula using AND OR NOT operators.
• De Morgan's laws: rules simplifying complex boolean expressions.
• Combinational circuit: a circuit whose output depends only on current inputs.
• Predictable output: a value determined purely by the inputs present.

Common misconceptions

• "A truth table lists one column for inputs." Truth tables list outputs as the final column.
• "De Morgan's laws apply to normal arithmetic." They apply only to boolean logic.
• "Combinational circuits have memory." Combinational circuits depend only on current inputs.

Teacher activities

1. Starter: ask what happens to an AND gate when one input is false.
2. Define AND, OR and NOT one by one and build truth tables.
3. Demonstrate De Morgan's laws by simplifying a compound expression.
4. Draw a simple AND circuit showing two inputs meeting at an output.
5. Contrast combinational circuits with sequential circuits briefly.
6. Close with the truth-table task and exit question.

Student activities

1. Answer the starter and explain why AND gives zero when any input is false.
2. Name the three basic gates and give the truth condition for each.
3. Complete truth tables for AND, OR and NOT.
4. Simplify a compound expression using De Morgan's laws step by step.
5. Draw a simple AND circuit and label the inputs and output.
6. Contrast combinational circuits with sequential circuits in one sentence.

Practical / learning evidence

Three complete truth tables, one De Morgan simplification with steps, one circuit drawing and a combinational versus sequential comparison. Submit all four for marking.

Resources and preparation

Printed truth tables, blank circuit templates and sample expressions. Offline route: paper versions, no device needed. Display any logic gates carefully and avoid touching circuit boards.

Assessment for learning

Inspect each truth table for every row filled correctly. Check the De Morgan simplification for valid steps. Mark the circuit for correct gates and connections. Flag any learner who claims a combinational circuit has memory.

Inclusion and homework

Provide the truth tables prefilled for the first row and allow oral completion of the rest. Reduce the circuit drawing to one simple gate. Extend confident learners with NAND and NOR combinations and a fourth truth-table exercise. Homework: simplify a second De Morgan expression and compare the two simplified results.