Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 2nd Term
Week: 8
Age: 15 years
Duration: 45 minutes
Subject: GSM Maintenance and Repairs
Curriculum Theme: Trade
Previous Lesson: Electronics Signs And Symbols: Types Of Diagrams And Symbols.
Topic: Power Supply and Amplifiers
Subject Matter: Constructional features of power supply, Uses of power supply, Basic power supply circuit

Specific Objectives

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

Cognitive Domain:

Define power supply.
State the constructional features of a power supply.
List at least three uses of power supply.
Describe the basic power supply circuit.

Affective Domain:

Appreciate the importance of power supply in electronic devices.
Show interest in learning about power supply circuits.

Psychomotor Domain:

Identify components of a power supply circuit.
Construct a basic power supply circuit using provided components.

Work cooperatively in groups to discuss power supply concepts.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (JSS 1-3) and Senior Secondary Education Curriculum for Technical Vocational Education (SSS 1-3).
State Unified Scheme of Work for GSM Maintenance and Repairs (SSS 1).
Anyanwu, A. (2018). Fundamentals of GSM Maintenance and Repairs for Senior Secondary Schools. Abuja: Excellent Publishers.
https://nigeriancurriculum.gov.ng/
https://www.waeconline.org.ng/e-learning

Instructional Materials

The teacher will teach this lesson with the aid of:

A functional power supply unit.
Transformer, rectifier diode, capacitor.
Printed Circuit Board (PCB) or breadboard.
Connecting wires and soldering iron (for practical demonstration).
Diagrams of power supply circuits.

Rationale for the Lesson

Understanding power supply is important because it enables pupils to know how electronic devices get the stable direct current they need to function. This knowledge helps them diagnose and repair common faults related to power in GSM devices and other electronics.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of electrical components like resistors, capacitors, and diodes, and understand the difference between AC and DC current.

Lesson Content/Board Summary

Power Supply and Amplifiers

Definition of Power Supply

A power supply is an electronic circuit or device that converts alternating current (AC) from the mains electricity to direct current (DC) of a specific voltage and current, suitable for powering electronic devices.

Constructional Features of a Power Supply

A typical power supply circuit consists of the following stages:

Transformer: This component steps down the high AC voltage from the mains to a lower, more suitable AC voltage for the circuit.
Rectifier: This stage converts the alternating current (AC) into pulsating direct current (DC). Common types include half-wave, full-wave (center-tapped), and bridge rectifiers.
Filter: The filter smooths out the pulsating DC from the rectifier, reducing ripples and making it a more stable DC output. Capacitors are commonly used as filter components.
Voltage Regulator: This stage maintains a constant DC output voltage despite changes in the input voltage or load current. Zener diodes and integrated circuit (IC) regulators are often used here.

Uses of Power Supply

Power supplies are essential in almost all electronic devices and systems. Their uses include:

Powering computers, laptops, and mobile phones.
Operating televisions, radios, and other home appliances.
Providing stable voltage for laboratory and testing equipment.
Charging batteries in various electronic devices.
Supplying power to industrial control systems and communication equipment.

Basic Power Supply Circuit

A basic unregulated DC power supply circuit comprises four main stages:

Transformer Stage: Reduces the high AC input voltage (e.g., 220V) to a lower AC voltage (e.g., 12V).
Rectifier Stage: Converts the reduced AC voltage into pulsating DC. A bridge rectifier made of four diodes is commonly used for efficiency.
Filter Stage: A large electrolytic capacitor is typically used to smooth the pulsating DC into a relatively steady DC voltage by storing and releasing charge.
Load: This is the electronic device or circuit that consumes the DC power from the power supply.

For a regulated power supply, a voltage regulator stage is added after the filter to ensure a constant output voltage.

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 what powers their mobile phones and other electronic gadgets. The teacher then introduces the topic: Power Supply and Amplifiers.
Pupils’ Activity: Pupils respond to the questions and listen attentively to the introduction.
Learning Point: Pupils are engaged and the topic is introduced.

Step 2: Explanation of Power Supply

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines what a power supply is, emphasizing its role in converting AC to DC. The teacher explains that most electronic devices require DC, while mains electricity is AC.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and basic function of a power supply.

Step 3: Constructional Features of a Power Supply

Time: 7 minutes
Teaching Skill: Elucidation/Identification
Teacher’s Activity: The teacher explains the main stages of a power supply circuit: transformer, rectifier, filter, and voltage regulator. The teacher uses diagrams or a physical power supply unit to point out these components.
Pupils’ Activity: Pupils observe the diagrams/components, identify them, and note down their functions.
Learning Point: Pupils identify and understand the function of each component in a power supply.

Step 4: Uses of Power Supply

Time: 6 minutes
Teaching Skill: Listing/Application
Teacher’s Activity: The teacher guides pupils to brainstorm and list various uses of power supplies in daily life and in electronic devices, linking it to GSM maintenance.
Pupils’ Activity: Pupils actively participate by mentioning different applications of power supplies.
Learning Point: Pupils understand the wide application of power supplies in various electronic systems.

Step 5: Basic Power Supply Circuit

Time: 7 minutes
Teaching Skill: Diagrammatic Explanation
Teacher’s Activity: The teacher draws and explains a simplified diagram of a basic power supply circuit, showing the flow from transformer to rectifier, filter, and load. The teacher explains the role of each stage in converting AC to smooth DC.
Pupils’ Activity: Pupils draw the circuit diagram in their notebooks and follow the teacher’s explanation.
Learning Point: Pupils can describe and sketch a basic power supply circuit.

Step 6: Practical Demonstration/Construction Guidance

Time: 5 minutes
Teaching Skill: Demonstration/Guidance
Teacher’s Activity: The teacher demonstrates how to identify the components (transformer, rectifier diode, capacitor) and briefly shows how they are connected on a breadboard or PCB to form a simple power supply circuit. The teacher guides pupils on safety precautions.
Pupils’ Activity: Pupils observe the demonstration and ask questions about the connections and components.
Learning Point: Pupils develop practical skills in identifying and connecting power supply components.

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 power supply.
Mention any three constructional features of a power supply.
List two uses of a power supply.
Describe the function of the rectifier in a power supply circuit.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 3 minutes
Teaching Skill: Summary/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework: “Draw a block diagram of a regulated power supply and label its parts.”
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: The lesson is concluded, and pupils have an assignment to reinforce learning.

Lesson Keywords

Power Supply – An electronic circuit that converts AC to DC to power electronic devices.
Transformer – An electrical device that transfers electrical energy between two or more circuits through electromagnetic induction, usually to change voltage levels.
Rectifier – An electronic device that converts alternating current (AC) into pulsating direct current (DC).
Filter – A circuit component (often a capacitor) used to smooth out pulsating DC, reducing ripples.
Voltage Regulator – A circuit or device that maintains a constant output voltage regardless of changes in input voltage or load current.
AC (Alternating Current) – Electric current that periodically reverses direction.
DC (Direct Current) – Electric current that flows in only one direction.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research different types of rectifiers (half-wave, full-wave bridge) and their applications. For pupils needing more support, the teacher can provide simplified diagrams and one-on-one guidance during the practical identification of components.

Note for teachers using this lesson plan

Ensure all safety precautions are observed during any practical demonstration involving electrical components. Have clear diagrams ready and ensure components are easily visible to all pupils. Encourage group discussion to foster collaborative learning.