Primary and Secondary Cells for SS 3

Class: SS 3
Term: First Term
Week: 5
Age: 16 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Electrical Energy Sources
Previous Lesson:
Topic: CELL
Subject Matter: Types of cell; primary and secondary cells. and secondary cells; Construction of a simple cell

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Define primary and secondary cells.
• Differentiate between primary and secondary cells.
• Describe the working principles of primary cells.
• Describe the working principles of secondary cells.
• Identify the components of a simple cell.

Psychomotor Domain

• Sketch a simple cell and label its parts.
• Construct a simple cell using available materials.

Affective Domain

• Appreciate the importance of cells in daily life and electrical systems.
• Demonstrate careful handling of cell components and chemicals.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Electrical Installation and Maintenance Work for Senior Secondary Schools, Book 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Primary cells (e.g., dry cell, button cell)
• Secondary cells (e.g., car battery, phone battery)
• Charts and posters illustrating different types of cells and their construction
• Materials for constructing a simple cell (e.g., lemon/potato, copper wire, zinc strip/galvanised nail, connecting wires, small LED or voltmeter)

Rationale for the Lesson

This lesson provides students with foundational knowledge of electrical cells, which are essential components in various electrical and electronic devices. Understanding primary and secondary cells, their operation, and construction principles is crucial for effective electrical installation and maintenance work. It equips students with practical skills and theoretical understanding necessary for future applications in the field.

Prerequisite/Previous Knowledge

Students should have a basic understanding of electricity, simple circuits, and the concept of conductors and insulators from their Junior Secondary School science classes.

Lesson Content/Board Summary

CELL

Types of Cells

Cells are devices that convert chemical energy into electrical energy through a chemical reaction. They are broadly classified into two main types:

1. Primary Cells: These are cells designed for single use and cannot be recharged. Once the chemical reactants are consumed, the cell stops producing electricity and is discarded.
2. Secondary Cells: These are rechargeable cells. Their chemical reactions can be reversed by applying an external electrical current, allowing them to be used multiple times.

Differences Between Primary and Secondary Cells

1. Rechargeability: Primary cells are non-rechargeable, while secondary cells are rechargeable.
2. Chemical Reaction: The chemical reaction in primary cells is irreversible, whereas in secondary cells, it is reversible.
3. Cost: Primary cells are generally cheaper per unit, but secondary cells offer long-term savings due to rechargeability.
4. Applications: Primary cells are used in low-drain, disposable devices (e.g., remote controls, flashlights). Secondary cells are used in high-drain, reusable devices (e.g., mobile phones, laptops, car batteries).

Working Principles of Cells

Working Principle of Primary Cells

Primary cells generate electricity through an irreversible chemical reaction between two different electrodes and an electrolyte. For example, in a simple Voltaic cell:

1. A zinc electrode (anode) and a copper electrode (cathode) are immersed in an electrolyte (e.g., dilute sulphuric acid or a lemon).
2. Zinc is more reactive than copper, so it loses electrons and gets oxidised, forming positive zinc ions in the electrolyte.
3. These electrons flow from the zinc electrode through an external circuit to the copper electrode.
4. At the copper electrode, positive hydrogen ions from the electrolyte gain electrons and are reduced, forming hydrogen gas.
5. This flow of electrons constitutes electric current. The reaction continues until one of the reactants is used up.

Working Principle of Secondary Cells

Secondary cells operate on reversible chemical reactions. They have two phases:

1. Discharging: During discharge, the cell converts chemical energy into electrical energy, similar to a primary cell. The electrodes undergo chemical changes as electrons flow through the external circuit.
2. Charging: During charging, an external electrical current is applied to the cell. This forces the chemical reaction to reverse, restoring the original chemical composition of the electrodes and electrolyte, thereby storing electrical energy as chemical energy.

Construction of a Simple Cell

A simple cell, often called a Voltaic or Galvanic cell, can be constructed using two different metals (electrodes) and an electrolyte. For instance, a lemon battery:

1. Electrodes: A copper strip/coin and a zinc strip/galvanised nail.
2. Electrolyte: The acidic juice inside a lemon.
3. Procedure:
   1. Insert the copper strip into one part of the lemon.
   2. Insert the zinc strip into another part of the lemon, ensuring the two metals do not touch inside the lemon.
   3. Connect one end of a connecting wire to the copper strip and the other end to one terminal of a small LED or voltmeter.
   4. Connect another connecting wire from the zinc strip to the other terminal of the LED or voltmeter.
   5. The LED should light up (if enough voltage is produced) or the voltmeter will show a reading, indicating current flow.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Activating Prior Knowledge

Teacher’s Activity: The teacher greets the students and asks them to recall what they know about sources of electricity and basic electrical components. The teacher then introduces the topic “CELL” as a fundamental source of electrical energy.

Pupils’ Activity: Students respond to questions about electricity and listen attentively to the introduction.

Learning Point: Introduction to cells

Step 2: Types of Cells

Time: 8 minutes

Teaching Skill: Explanation/Classification

Teacher’s Activity: The teacher explains the two main types of cells: primary and secondary cells, using real-life examples (e.g., dry cells, car batteries) and charts. The teacher defines each type and highlights their key characteristics.

Pupils’ Activity: Students observe the examples, listen to the explanations, and ask questions for clarification.

Learning Point: Primary and secondary cells

Step 3: Differences Between Primary and Secondary Cells

Time: 7 minutes

Teaching Skill: Comparison/Differentiation

Teacher’s Activity: The teacher guides students to identify and discuss the major differences between primary and secondary cells, focusing on rechargeability, chemical reactions, cost, and typical applications. The teacher uses a comparison chart if available.

Pupils’ Activity: Students participate in the discussion, contributing their understanding of the differences and noting key points.

Learning Point: Cell type distinctions

Step 4: Working Principles of Primary Cells

Time: 7 minutes

Teaching Skill: Explanation/Illustration

Teacher’s Activity: The teacher explains the working principle of primary cells, using a simple Voltaic cell as an example. The teacher describes how chemical reactions between electrodes and electrolytes generate electric current.

Pupils’ Activity: Students observe diagrams or illustrations and listen to the explanation of how primary cells work.

Learning Point: Primary cell operation

Step 5: Working Principles of Secondary Cells

Time: 5 minutes

Teaching Skill: Explanation

Teacher’s Activity: The teacher explains the working principle of secondary cells, focusing on the reversible nature of their chemical reactions during discharge and charge cycles. The teacher highlights how they store and release energy.

Pupils’ Activity: Students listen and understand the concept of charging and discharging in secondary cells.

Learning Point: Secondary cell operation

Step 6: Construction of a Simple Cell

Time: 8 minutes

Teaching Skill: Demonstration/Practical Activity

Teacher’s Activity: The teacher demonstrates the construction of a simple cell (e.g., a lemon battery) using the prepared materials. The teacher explains each step and the role of the components. Students are encouraged to observe closely and ask questions.

Pupils’ Activity: Students observe the demonstration of simple cell construction and identify the parts involved.

Learning Point: Simple cell construction

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity:H The teacher evaluates the learning by asking the following questions:

1. What is the main difference between a primary cell and a secondary cell?
2. Give two examples of primary cells.
3. Give two examples of secondary cells.
4. Briefly explain how a simple primary cell generates electricity.
5. Mention two components needed to construct a simple cell.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Understanding cell types and principles

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on types, differences, and working principles of cells, and construction of a simple cell, into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson content

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Consolidation

Teacher’s Activity: The teacher summarises the key points of the lesson, reiterating the importance of understanding primary and secondary cells in electrical installation. The teacher encourages students to explore more about different types of cells.

Pupils’ Activity: Students listen to the summary and prepare for the next lesson.

Learning Point: Lesson recap

Continuous Assessment/Further Study

Type: Homework/Practical Exercise

Instruction: Answer the following questions and attempt the practical task:

1. Explain the charging and discharging process in a secondary cell.
2. List three applications for primary cells and three for secondary cells in modern technology.
3. Research and identify one specific type of primary cell (e.g., Alkaline cell) and one specific type of secondary cell (e.g., Lithium-ion cell), describing their internal components.
4. Practical Task: Using readily available materials like lemons/potatoes, copper wires, and galvanised nails, construct a simple cell at home and try to power a small LED. Document your process and observations.

Lesson Keywords

• Cell – A device that converts chemical energy into electrical energy.
• Primary Cell – A non-rechargeable cell designed for single use.
• Secondary Cell – A rechargeable cell whose chemical reactions can be reversed.
• Electrolyte – A substance that contains ions and can conduct electricity.
• Electrode – A conductor through which electricity enters or leaves an electrolyte.
• Anode – The negative electrode where oxidation occurs (electrons are lost).
• Cathode – The positive electrode where reduction occurs (electrons are gained).

Differentiation

For learners who need additional support, the teacher will provide simplified diagrams and focus on the core definitions and basic differences between primary and secondary cells. Faster learners will be encouraged to research specific types of cells (e.g., lead-acid, lithium-ion) and their detailed chemical reactions, as well as explore series and parallel connections of cells.

Suggested Lesson Videos

For further understanding, students can search on YouTube for:

• “Primary and Secondary Cells explained”
• “How a simple voltaic cell works”
• “Building a lemon battery”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have gathered various types of primary and secondary cells, charts, and materials for constructing a simple cell (e.g., lemon, copper wire, zinc strip, small LED). Begin by engaging students with their prior knowledge of electricity. Systematically introduce primary and secondary cells, clearly defining each and highlighting their differences. Use the demonstration of a simple cell construction to make the concept concrete and practical. Emphasise safety when handling chemicals and electrical components during the practical activity. Allow students to observe and ask questions throughout the demonstration. During Step 7, assess understanding using the provided questions, and provide immediate feedback. Students should copy the Board Summary notes in Step 8. For weaker learners, provide extra visual aids and simplify explanations. Challenge faster learners with additional research questions or by exploring more complex cell types. Ensure all students grasp the fundamental distinction and working principles of cells before concluding the lesson.