Class: Senior Secondary School 1 (SS1 / SSS1)
Term: 2nd Term
Week: 2
Age: 15 years
Duration: 45 minutes
Subject: GSM Maintenance And Repairs
Curriculum Theme: Trade
Previous Lesson: Principles Of AC And DC Quantities: Meaning Of AC And DC Quantities.
Topic: The principles of AC and DC quantities
Subject Matter: Differences between AC and DC, Characteristics of AC, Characteristics of DC

Specific Objectives

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

Cognitive Domain:

Define Alternating Current (AC) and Direct Current (DC).
State at least three characteristics of Alternating Current (AC).
State at least three characteristics of Direct Current (DC).
Differentiate between Alternating Current (AC) and Direct Current (DC).

Affective Domain:

Appreciate the importance of understanding AC and DC in electronic devices.
Show interest in identifying various AC and DC power sources.

Psychomotor Domain:

Identify common AC and DC power sources from given examples.

Participate actively in class discussions about AC and DC applications.
Collaborate with peers to list devices that use AC and DC.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for GSM Maintenance and Repairs.
State Unified Scheme of Work for Senior Secondary School GSM Maintenance and Repairs.
Akinola, P.O. (2018). Basic Electronics and GSM Repairs for Senior Secondary Schools. Lagos: Macmillian Publishers.

Instructional Materials

The teacher will teach this lesson with the aid of:

AC adapter
DC power pack
Charts showing AC and DC waveforms
Test leads

Rationale for the Lesson

This lesson helps pupils understand the fundamental types of electrical current that power electronic devices, including mobile phones. Knowing the differences between AC and DC is important for diagnosing power-related issues and safely handling electrical components in GSM maintenance.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of electricity, simple circuits, and common power sources like batteries.

Lesson Content/Board Summary

The Principles of AC and DC Quantities

Alternating Current (AC)

Alternating current (AC) is an electric current that periodically reverses its direction and continuously changes its magnitude with time. It is the type of current supplied to homes and businesses.

The characteristics of Alternating Current (AC) are:

It continuously changes its magnitude and direction.
It has a specific frequency, typically 50 Hz or 60 Hz, meaning it completes 50 or 60 cycles per second.
It can be easily transformed to higher or lower voltages using transformers.
It is represented by a sinusoidal (wave-like) waveform.
It does not have fixed positive and negative terminals (polarity changes).

Examples of AC sources include power outlets in homes and offices, and electrical generators.

Direct Current (DC)

Direct current (DC) is an electric current that flows in only one constant direction. The voltage is typically steady over time.

The characteristics of Direct Current (DC) are:

It flows in a constant, single direction.
Its voltage magnitude is typically steady over time (constant).
It has no frequency, as its direction does not change.
It is difficult to transform to higher or lower voltages without complex electronic circuits.
It has fixed positive (+) and negative (-) terminals (fixed polarity).

Examples of DC sources include batteries, solar cells, and rectified AC power supplies (like phone chargers).

Differences between AC and DC

The main differences between Alternating Current (AC) and Direct Current (DC) are:

Direction of Flow: AC periodically reverses direction, while DC flows in one constant direction.
Voltage Magnitude: AC voltage continuously changes, while DC voltage is typically constant.
Frequency: AC has a frequency (e.g., 50 Hz in Nigeria), while DC has zero frequency.
Transformation: AC can be easily transformed (stepped up or down) using transformers; DC cannot be easily transformed without complex circuits.
Polarity: AC polarity continuously changes; DC has fixed positive and negative polarity.
Sources: AC comes from power generators and wall sockets; DC comes from batteries, solar cells, and rectified power supplies.

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 reviews the previous lesson briefly. The teacher then introduces the topic by asking pupils about common power sources they use daily (e.g., wall sockets, phone batteries) and explains that these sources provide different types of electricity.
Pupils’ Activity: Pupils respond to questions and listen attentively to the introduction.
Learning Point: Pupils recall previous knowledge and are prepared for the new topic.

Step 2: Presentation of Alternating Current (AC)

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines Alternating Current (AC) and explains its key characteristics using charts showing AC waveforms. The teacher shows an AC adapter as an example of a device that uses AC input.
Pupils’ Activity: Pupils listen, observe the charts, and ask questions for clarification.
Learning Point: Pupils understand the definition and characteristics of AC.

Step 3: Presentation of Direct Current (DC)

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines Direct Current (DC) and explains its key characteristics, contrasting it with AC. The teacher shows a DC power pack or a battery as an example of a DC source.
Pupils’ Activity: Pupils listen, observe, and note down important points.
Learning Point: Pupils understand the definition and characteristics of DC.

Step 4: Comparison of AC and DC

Time: 10 minutes
Teaching Skill: Comparative Analysis/Discussion
Teacher’s Activity: The teacher facilitates a discussion to highlight the differences between AC and DC, using a comparison chart or by listing points on the board. The teacher guides pupils to identify the practical implications of these differences.
Pupils’ Activity: Pupils actively participate in the discussion, contributing points and asking questions to clarify the differences.
Learning Point: Pupils can clearly differentiate between AC and DC based on their properties.

Step 5: Practical Identification of AC and DC Sources

Time: 5 minutes
Teaching Skill: Practical Application
Teacher’s Activity: The teacher displays various power sources (e.g., wall socket, phone battery, AC adapter, DC power supply) and asks pupils to identify whether each provides AC or DC.
Pupils’ Activity: Pupils identify and state whether the displayed items are AC or DC sources, explaining their reasoning.
Learning Point: Pupils can practically identify common AC and DC power sources.

Step 6: Class Activity/Discussion on Applications

Time: 4 minutes
Teaching Skill: Group Work/Collaboration
Teacher’s Activity: The teacher divides pupils into small groups and asks them to list devices they use daily that are powered by AC and those powered by DC, specifically mentioning their relevance to GSM.
Pupils’ Activity: Pupils discuss in groups and present their lists to the class.
Learning Point: Pupils understand the real-world applications of AC and DC.

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 Alternating Current (AC).
List three characteristics of Direct Current (DC).
State two differences between AC and DC.
Give two examples of AC sources and two examples of DC sources.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of understanding AC and DC in electronics and GSM maintenance. The teacher assigns homework: “Draw simple diagrams of an AC waveform and a DC waveform.”
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their understanding of the topic.

Lesson Keywords

AC – Alternating Current, an electric current that periodically reverses direction.
DC – Direct Current, an electric current that flows in only one constant direction.
Frequency – The number of cycles per second for an AC current, measured in Hertz (Hz).
Polarity – The positive or negative terminal of a DC source.
Waveform – The shape of the graph of current or voltage over time.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional questions on the applications of AC and DC in specific GSM components. For pupils needing more support, the teacher will use more visual aids and provide one-on-one guidance during practical identification and group activities.

Note for teachers using this lesson plan

Ensure that all safety precautions are observed when demonstrating with electrical components. Emphasize the practical relevance of AC and DC to the repair and maintenance of GSM devices. Encourage pupils to bring examples of AC adapters and DC batteries from home (under supervision) for a more interactive session.