Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 2nd Term
Week: 1
Age: 15 years
Duration: 45 minutes
Subject: GSM Maintenance and Repairs
Curriculum Theme: Trade
Previous Lesson: .
Topic: Principles of AC and DC quantities
Subject Matter: Meaning of AC quantities, Meaning of DC quantities, Basic principles of AC, Basic principles 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) quantities.
Explain the basic principles of AC.
Explain the basic principles of DC.

Affective Domain:

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

Psychomotor Domain:

Identify AC power sources.
Identify DC power sources.

Discuss the applications of AC and DC in everyday devices.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (JSS 1-3)
National Senior Secondary Education Curriculum for Trade and Entrepreneurship (GSM Maintenance)
State Unified Scheme of Work for Senior Secondary Schools
GSM Maintenance and Repairs for Senior Secondary Schools by [Author/Publisher, e.g., F.N. Okoro]
https://www.electrical4u.com/alternating-current-vs-direct-current/
https://www.explainthatstuff.com/alternating-current-vs-direct-current.html

Instructional Materials

The teacher will teach this lesson with the aid of:

AC power source (e.g., wall socket, small AC adapter)
DC battery (e.g., AA battery, phone battery)
Connecting wires
Multimeter
Charts showing AC and DC waveforms

Rationale for the Lesson

This lesson helps pupils understand the fundamental types of electrical currents used in electronics, including GSM devices. Understanding AC and DC is important for diagnosing faults and safely working with electrical components in various applications.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of electricity and simple circuits from previous classes.

Lesson Content/Board Summary

Principles of AC and DC Quantities

Meaning of AC Quantities

Alternating Current (AC) is an electric current that periodically reverses direction and continuously changes its magnitude with time, in contrast to direct current, which flows only in one direction.

The following are characteristics of AC quantities:

Direction of flow changes periodically.
Magnitude varies continuously over time.
Can be easily stepped up or down using transformers.
Used for transmitting power over long distances.
Commonly found in household electrical outlets.

Meaning of DC Quantities

Direct Current (DC) is an electric current that flows in only one direction. The magnitude of a pure DC current is constant over time.

The following are characteristics of DC quantities:

Direction of flow is constant.
Magnitude is steady (constant) over time for pure DC.
Cannot be easily stepped up or down using simple transformers.
Often used in battery-powered devices and electronic circuits.
Commonly found in batteries, solar cells, and rectified AC.

Basic Principles of AC

The following are basic principles of AC:

Generation: AC is typically generated by alternators (AC generators) which use electromagnetic induction to produce a constantly changing voltage.
Waveform: The most common AC waveform is a sine wave, representing the periodic variation of voltage and current.
Frequency: AC has a specific frequency, which is the number of cycles per second (measured in Hertz, Hz). In Nigeria, the standard frequency is 50 Hz.
Transformation: AC voltage can be easily increased or decreased using transformers, making it efficient for power transmission.

Basic Principles of DC

The following are basic principles of DC:

Generation: DC can be generated by batteries (chemical reaction), solar cells (photovoltaic effect), or by rectifying (converting) AC into DC using diodes and filters.
Polarity: DC circuits have a definite positive and negative terminal, and current flows from positive to negative.
Steady State: In a pure DC circuit, the voltage and current remain constant over time once the circuit is established.
Applications: DC is essential for most electronic devices, including computers, mobile phones, and electric vehicles, as their internal components require a stable, unidirectional current.

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 asks pupils what they know about electricity and gives examples of devices that use electricity, guiding them towards different types of power. The teacher introduces the topic: Principles of AC and DC quantities.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils are prepared for the lesson and recall previous knowledge.

Step 2: Meaning of AC Quantities

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines Alternating Current (AC) and explains its key characteristics, such as changing direction and magnitude. The teacher gives examples of AC sources like household sockets.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and characteristics of AC.

Step 3: Meaning of DC Quantities

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines Direct Current (DC) and explains its key characteristics, such as constant direction and steady magnitude. The teacher gives examples of DC sources like batteries.
Pupils’ Activity: Pupils listen, take notes, and differentiate between AC and DC.
Learning Point: Pupils understand the definition and characteristics of DC.

Step 4: Basic Principles of AC

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains the basic principles of AC, including how it is generated, its common waveform (sine wave), frequency, and its ability to be transformed using transformers. The teacher may use charts to illustrate the sine wave.
Pupils’ Activity: Pupils observe the charts, listen, and note down the principles.
Learning Point: Pupils grasp the fundamental principles governing AC.

Step 5: Basic Principles of DC

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains the basic principles of DC, covering its generation (batteries, rectification), polarity, steady state nature, and common applications in electronic devices.
Pupils’ Activity: Pupils listen, take notes, and ask questions.
Learning Point: Pupils understand the fundamental principles governing DC.

Step 6: Practical Demonstration and Identification

Time: 5 minutes
Teaching Skill: Demonstration/Observation
Teacher’s Activity: The teacher demonstrates an AC power source (e.g., plugging in an AC adapter) and a DC power source (e.g., a battery). The teacher uses a multimeter to show the voltage readings for both AC and DC, highlighting the difference.
Pupils’ Activity: Pupils observe the demonstration, identify the AC and DC sources, and note the readings.
Learning Point: Pupils can practically identify AC and DC sources.

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).
State two characteristics of Direct Current (DC).
Mention two basic principles of AC.
Give an example of an AC power source and a DC power source.

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 briefly summarizes the main points of the lesson on AC and DC quantities and their principles. The teacher assigns homework: List five devices that primarily use AC and five that primarily use DC.
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and have follow-up tasks.

Lesson Keywords

Alternating Current (AC) – An electric current that periodically reverses direction.
Direct Current (DC) – An electric current that flows in only one direction.
Waveform – The shape of a wave, such as a sine wave for AC.
Frequency – The number of cycles per second for an AC current, measured in Hertz.
Polarity – The positive and negative terminals of a DC source.

Differentiation

The teacher will provide additional support to struggling pupils by simplifying explanations and offering more practical examples. Advanced pupils will be encouraged to research real-world applications of AC and DC in GSM technology.

Note for teachers using this lesson plan

Ensure all instructional materials are available and in working condition before the lesson. Emphasize safety precautions when handling electrical sources during demonstrations. Encourage pupils to actively participate and ask questions.