Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 1st Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Basic Electronics
Curriculum Theme: Basic Electronics
Previous Lesson: Conductors and Insulators: Uses in Daily Life.
Topic: ELECTRIC CURRENT: Direct and Alternating Current.
Subject Matter: meaning of direct current, meaning of alternating current, diagrams showing DC and AC sources, distinguishing direct current from alternating current.

Specific Objectives

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

Cognitive Domain:

Define Direct Current (DC).
Define Alternating Current (AC).
State the differences between Direct Current and Alternating Current.

Affective Domain:

Appreciate the importance of distinguishing between DC and AC in electrical applications.
Show willingness to participate in class discussions about current types.

Psychomotor Domain:

Draw simple diagrams representing DC and AC waveforms.
Identify sources of DC and AC from given examples.

Collaborate with peers to answer questions about electric current.
Engage respectfully in discussions on the topic.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Electronics (Senior Secondary).
State Unified Scheme of Work for Basic Electronics, SSS 1.
D.N.O. Anukwu (2009). Basic Electronics for Senior Secondary Schools. Evans Brothers (Nigeria Publishers) Limited.
https://www.electrical4u.com/direct-current-vs-alternating-current/
https://www.electronics-tutorials.ws/dccircuits/direct-current.html

Instructional Materials

The teacher will teach this lesson with the aid of:

Dry cells
Batteries
Charts showing sources of alternating current (e.g., power socket, generator diagram)
Charts showing diagrams of DC and AC waveforms
Whiteboard/Blackboard
Markers/Chalk

Rationale for the Lesson

This lesson helps pupils understand the fundamental differences between direct and alternating current, which are essential concepts in electronics. Knowing these differences enables pupils to comprehend how various electrical devices work and the types of power they use in their daily lives.

Prerequisite/Previous Knowledge

Pupils are assumed to have basic knowledge of electricity, simple circuits, and the concept of electric charge flow.

Lesson Content/Board Summary

ELECTRIC CURRENT: Direct and Alternating Current

1. Meaning of Direct Current (DC)

Direct current (DC) is the flow of electric charge that moves in only one constant direction. The voltage level typically remains steady over time.

Characteristics of DC include:

The current flows in a single, unchanging direction.
The voltage magnitude is constant or nearly constant over time.

Common sources of DC are:

Batteries
Dry cells
Solar cells
DC power supplies (e.g., phone chargers)

2. Meaning of Alternating Current (AC)

Alternating current (AC) is the flow of electric charge that periodically reverses its direction. The voltage magnitude also changes periodically, typically in a sinusoidal (sine wave) pattern.

Characteristics of AC include:

The direction of current flow changes regularly.
The voltage magnitude varies over time, oscillating between positive and negative values.

Common sources of AC are:

Electrical generators (alternators)
Mains electricity supply from wall sockets
Power plants

3. Diagrams Showing DC and AC Sources/Waveforms

The waveform of Direct Current (DC) is typically represented as a straight horizontal line on a voltage-time graph, indicating constant voltage. The symbol for a DC source is often a battery symbol.

The waveform of Alternating Current (AC) is typically represented as a sine wave on a voltage-time graph, showing its periodic change in direction and magnitude. The symbol for an AC source is a circle with a sine wave inside.

4. Distinguishing Direct Current from Alternating Current

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

Direction of Flow: DC flows in one direction, while AC periodically reverses its direction.
Voltage Variation: DC voltage is constant over time, while AC voltage varies over time (e.g., sinusoidally).
Frequency: DC has zero frequency, meaning no cycles per second. AC has a specific frequency (e.g., 50 Hz or 60 Hz).
Generation: DC is typically generated by batteries, solar cells, and rectifiers. AC is typically generated by alternators and power generators.
Applications: DC is used in electronic circuits, batteries, and low-power devices. AC is used for power transmission over long distances and for most household appliances and industrial machinery.

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 they understand by electric current. The teacher then introduces the topic: “ELECTRIC CURRENT: Direct and Alternating Current,” explaining that not all electricity behaves in the same way.
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively to the introduction of the new topic.
Learning Point: Pupils recall prior knowledge about electric current and are introduced to the lesson topic.

Step 2: Meaning of Direct Current (DC)

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines Direct Current (DC) and explains its characteristics. The teacher uses dry cells and batteries as examples, demonstrating how they provide DC. A simple diagram of a DC waveform is drawn on the board.
Pupils’ Activity: Pupils listen to the explanation, observe the demonstrations, and copy notes from the board. They may ask questions for clarification.
Learning Point: Pupils understand the definition and characteristics of Direct Current (DC) and identify its sources.

Step 3: Meaning of Alternating Current (AC)

Time: 10 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher defines Alternating Current (AC) and explains its characteristics, contrasting it with DC. The teacher shows charts displaying sources of AC (e.g., wall socket, generator) and draws a simple diagram of an AC waveform (sine wave) on the board.
Pupils’ Activity: Pupils pay attention to the explanation, observe the charts, and copy notes and diagrams from the board.
Learning Point: Pupils understand the definition and characteristics of Alternating Current (AC) and identify its sources.

Step 4: Diagrams Showing DC and AC Sources/Waveforms

Time: 5 minutes
Teaching Skill: Visualisation/Illustration
Teacher’s Activity: The teacher explicitly compares the diagrams of DC and AC waveforms on the board, pointing out the constant nature of DC versus the periodic variation of AC. The teacher also shows symbols for DC and AC sources.
Pupils’ Activity: Pupils observe the diagrams and note the visual differences between DC and AC representations.
Learning Point: Pupils can visually distinguish between DC and AC waveforms and symbols.

Step 5: Distinguishing Direct Current from Alternating Current

Time: 5 minutes
Teaching Skill: Comparison/Analysis
Teacher’s Activity: The teacher facilitates a discussion to highlight the key differences between DC and AC, focusing on direction of flow, voltage variation, frequency, and typical applications. The teacher lists these differences on the board.
Pupils’ Activity: Pupils participate in the discussion, contributing their understanding of the differences, and copy the points from the board.
Learning Point: Pupils can state and explain the differences between DC and AC.

Step 6: Class Activity/Discussion

Time: 2 minutes
Teaching Skill: Collaboration/Application
Teacher’s Activity: The teacher asks pupils to briefly discuss with their seatmates one device that uses DC and one that uses AC, and why.
Pupils’ Activity: Pupils engage in a short discussion and share their examples with the class.
Learning Point: Pupils apply their knowledge to real-world examples.

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 Direct Current (DC).
Mention two sources of Alternating Current (AC).
State two differences between DC and AC.
Draw a simple diagram showing the waveform of Direct Current.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 3 minutes
Teaching Skill: Summarization/Consolidation
Teacher’s Activity: The teacher summarizes the key learning points of the lesson, reiterating the definitions and differences between DC and AC. The teacher assigns homework: “List five household appliances and state whether they primarily use DC or AC.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their understanding of the lesson and are given an opportunity for further practice.

Lesson Keywords

Direct Current (DC) – Electric current that flows in only one constant direction.
Alternating Current (AC) – Electric current that periodically reverses its direction.
Waveform – A graphical representation of the change in a varying quantity (like voltage or current) over time.
Battery – A device that converts chemical energy into electrical energy, providing direct current.
Generator – A machine that converts mechanical energy into electrical energy, often producing alternating current.

Differentiation

For pupils who grasp the concepts quickly, the teacher can ask them to research practical applications where DC is converted to AC or vice-versa. For pupils who need more support, the teacher will provide simplified diagrams and additional examples, ensuring they understand the basic definitions and differences before moving on.

Note for teachers using this lesson plan

Ensure that the diagrams drawn on the board for DC and AC waveforms are clear and distinct. Use the physical dry cells and batteries to make the concept of DC tangible. Encourage pupils to ask questions to clarify any misconceptions. Emphasize the real-world relevance of understanding DC and AC, as this helps in career choices in electronics and engineering.