Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 3rd Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Basic Electricity
Curriculum Theme: Basic Electricity
Previous Lesson: Trans.
Topic: TRANSFORMERS
Subject Matter: constructional features of transformer, transformer core, primary and secondary windings, insulation and casing, prototype construction steps overview

Specific Objectives

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

Cognitive Domain:

Define a transformer.
Identify the main constructional features of a transformer.
List the key components of a simple transformer.

Affective Domain:

Appreciate the importance of transformers in electrical systems.
Show interest in understanding the internal structure of electrical devices.

Psychomotor Domain:

Identify the primary and secondary windings, core, and casing of a transformer model.
Outline the basic steps for assembling a simple transformer prototype.

Participate actively in class discussions related to transformer construction.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Senior Secondary Schools.
State Unified Scheme of Work for Basic Electricity SSS 1.
Basic Electricity for Senior Secondary Schools, Book 1.

Instructional Materials

The teacher will teach this lesson with the aid of:

A sample step-down transformer.
Circuit diagrams illustrating transformer construction.
Iron core materials.
Insulated copper wire.
Insulating tape.
Basic tools (e.g., wire strippers).
A simple assembled transformer prototype.

Rationale for the Lesson

This lesson helps pupils understand how transformers are built and how they work to change voltage levels. This knowledge is important because transformers are essential components in power transmission and in many electronic devices used in daily life.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of electricity, including concepts of voltage and current, and have been introduced to the idea of electromagnetic induction.

Lesson Content/Board Summary

TRANSFORMERS

Definition of a Transformer

A transformer is a static electrical device that transfers electrical energy from one circuit to another through electromagnetic induction, usually with a change in voltage and current.

Constructional Features of a Transformer

The main constructional features of a simple transformer include the core, primary winding, secondary winding, insulation, and casing.

Transformer Core

The transformer core provides a low-reluctance path for the magnetic flux. It is typically made of laminated soft iron or silicon steel sheets to reduce eddy current losses.

Common types of transformer cores are:

Shell-type core: Both windings are wound on the central limb.
Core-type core: Windings are wound on two separate limbs of the core.

Primary and Secondary Windings

The windings are coils of insulated copper wire. They are wound around the transformer core.

Primary Winding: This is the coil connected to the input alternating current (AC) supply.
Secondary Winding: This is the coil from which the output voltage is obtained. The number of turns in the primary and secondary windings determines whether the transformer is a step-up (more turns in secondary) or step-down (fewer turns in secondary) transformer.

Insulation and Casing

Insulation materials (e.g., varnish, paper, plastic tape) are used to prevent short circuits between the turns of the windings and between the windings and the core. The casing protects the internal components from environmental factors and provides mechanical support.

Overview of Steps for Constructing a Simple Transformer Prototype

Constructing a simple transformer prototype involves the following general steps:

Obtaining a suitable laminated iron core.
Winding the primary coil with a specific number of turns of insulated copper wire around one limb of the core.
Insulating the primary winding from the secondary winding.
Winding the secondary coil with a different number of turns of insulated copper wire around the same or another limb of the core.
Securing the windings with insulating tape.
Connecting the ends of the coils to terminals for input and output.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to recall their previous lesson on electromagnetic induction. The teacher then asks if they know any devices that can change voltage levels in their homes or schools.
Pupils’ Activity: Pupils respond to the questions, sharing their prior knowledge and ideas.
Learning Point: Pupils connect the new lesson to previous knowledge and are introduced to the concept of voltage transformation.

Step 2: Definition of a Transformer

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines a transformer as a static electrical device that transfers electrical energy between circuits, usually changing voltage and current levels. The teacher explains that this process relies on electromagnetic induction.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the basic definition and function of a transformer.

Step 3: Constructional Features of a Transformer

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher displays a sample transformer or a detailed diagram and points out its main constructional features: the core, primary winding, secondary winding, insulation, and casing. The teacher briefly explains the role of each part.
Pupils’ Activity: Pupils observe the sample/diagram, identify the parts, and listen to the explanations.
Learning Point: Pupils can identify the major physical components of a transformer.

Step 4: Transformer Core

Time: 7 minutes
Teaching Skill: Elaboration/Illustration
Teacher’s Activity: The teacher explains the function of the transformer core, emphasizing that it provides a path for magnetic flux. The teacher discusses that cores are typically made of laminated soft iron to reduce energy losses and mentions core-type and shell-type constructions.
Pupils’ Activity: Pupils pay attention, ask questions about the core material and types, and take notes.
Learning Point: Pupils understand the purpose and basic types of transformer cores.

Step 5: Primary and Secondary Windings, Insulation, and Casing

Time: 8 minutes
Teaching Skill: Explanation/Questioning
Teacher’s Activity: The teacher elaborates on the primary and secondary windings, explaining their connection to the input and output. The teacher also discusses the importance of insulation for safety and preventing short circuits, and the role of the casing. The teacher asks pupils to explain the difference between primary and secondary windings.
Pupils’ Activity: Pupils listen, respond to questions, and note down the functions of windings, insulation, and casing.
Learning Point: Pupils understand the roles of the windings, insulation, and casing in a transformer.

Step 6: Prototype Construction Steps Overview

Time: 5 minutes
Teaching Skill: Guided Discussion/Visualization
Teacher’s Activity: The teacher presents a simplified overview of the steps involved in constructing a simple transformer prototype, using the instructional materials (iron core, wire, tape) to illustrate the process. The teacher focuses on the sequence of winding and insulating.
Pupils’ Activity: Pupils observe the materials, visualize the construction process, and ask questions about the steps.
Learning Point: Pupils gain a general understanding of how a simple transformer model can be assembled.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

Define a transformer.
Mention any three constructional features of a transformer.
State the main purpose of the transformer core.
Distinguish between the primary and secondary windings of a transformer.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Consolidation
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the definition and main parts of a transformer. The teacher assigns homework: “Draw a labelled diagram showing the main parts of a core-type transformer.”
Pupils’ Activity: Pupils listen to the summary, ask any final questions, and copy the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

Transformer – An electrical device that transfers energy between circuits with a change in voltage and current.
Core – The laminated iron or steel part that provides a path for magnetic flux.
Primary Winding – The coil connected to the input AC supply.
Secondary Winding – The coil from which the output voltage is obtained.
Insulation – Material used to prevent electrical short circuits between windings and core.

Differentiation

For visual learners, the teacher will use diagrams, a real transformer model, and materials for prototype construction. Auditory learners will benefit from clear explanations and discussions. Kinesthetic learners will be engaged during the overview of prototype construction steps, potentially handling materials. Struggling pupils will receive additional guidance and simplified explanations, while advanced pupils can be challenged to research different types of transformers or their applications.

Note for teachers using this lesson plan

Ensure a clear, visible sample transformer or large, well-labelled diagrams are available. When discussing prototype construction, focus on the principles rather than detailed practical instructions, as the goal is an overview. Emphasize safety precautions if handling any electrical components. Encourage pupils to ask questions to clarify concepts.