Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: First Term
Week: 5
Age: 15 years
Duration: 45 minutes
Subject: Basic Electronics
Curriculum Theme: Basic Electronics
Previous Lesson: Electric Current: Direct and Alternating Current.
Topic: ELECTRIC CURRENT: Differences between Direct Current (D.C) and Alternating Current (A.C)
Subject Matter: Differences between direct current and alternating current, characteristics of DC, characteristics of AC, examples of DC use, examples of AC use

Specific Objectives

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

Cognitive Domain:

Define Direct Current (DC) and Alternating Current (AC).
State at least three characteristics of Direct Current (DC).
State at least three characteristics of Alternating Current (AC).
List at least three key differences between DC and AC.
Identify at least two examples of DC uses and two examples of AC uses.

Affective Domain:

Show interest in understanding the types of electric current used daily.
Appreciate the importance of distinguishing between DC and AC for electrical safety and applications.

Psychomotor Domain:

Draw simple graphical representations of DC and AC waveforms.
Identify sources of DC and AC from given diagrams or actual components.

Participate actively in group discussions about the types of electric current.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (Senior Secondary Education)
State Unified Scheme of Work for Basic Electronics SSS 1
Basic Electronics for Senior Secondary Schools by A. O. Oloruntoba

Instructional Materials

The teacher will teach this lesson with the aid of:

Dry cells
Batteries
Charts showing AC sources (e.g., wall socket, generator)
Charts illustrating DC and AC waveforms
Whiteboard/chalkboard and markers/chalk

Rationale for the Lesson

This lesson helps pupils understand the two main types of electric current they encounter daily, which is important for understanding how various electrical devices work. Distinguishing between direct and alternating current enables pupils to make informed decisions about electrical safety and appropriate power sources for different applications.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of electricity, electric circuits, and the concept of current flow from previous lessons.

Lesson Content/Board Summary

ELECTRIC CURRENT: Direct Current (DC) and Alternating Current (AC)

Direct Current (DC)

Direct Current (DC) is an electric current that flows in only one direction, maintaining a constant polarity. The voltage remains constant or varies smoothly without changing direction.

The following are characteristics of Direct Current (DC):

It flows in a single, constant direction.
Its voltage polarity remains constant (positive and negative terminals do not switch).
It has a constant magnitude or varies smoothly without changing direction.
It has zero frequency.

Alternating Current (AC)

Alternating Current (AC) is an electric current that periodically reverses its direction of flow. The voltage polarity also reverses periodically.

The following are characteristics of Alternating Current (AC):

It periodically reverses its direction of flow.
Its voltage polarity continuously changes (positive and negative terminals switch).
It continuously changes in magnitude over time, typically in a sinusoidal waveform.
It has a specific frequency (e.g., 50 Hz or 60 Hz).

Differences between DC and AC

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

Direction of Flow: DC flows in one direction; AC reverses direction periodically.
Polarity: DC has constant polarity; AC polarity reverses periodically.
Magnitude: DC is usually constant; AC continuously changes magnitude over time.
Frequency: DC has zero frequency; AC has a specific frequency.
Transmission: AC can be transmitted over long distances more efficiently at high voltages; DC is less efficient for long-distance high-voltage transmission.

Examples of DC Uses

The following are examples of devices and systems that use DC:

Batteries (e.g., in phones, laptops, cars)
Solar cells
LED lights
Electronic circuits (e.g., computers, TVs, radios)
Electric vehicles

Examples of AC Uses

The following are examples of devices and systems that use AC:

Household power outlets
Large appliances (e.g., refrigerators, air conditioners)
Electric motors (e.g., in fans, washing machines)
Power transmission grids
Generators (produce AC)

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 what they learned about electric current in the previous lesson. The teacher then asks pupils to identify various electrical devices in the classroom and at home and prompts them to think about how these devices get power.
Pupils’ Activity: Pupils respond to questions, recalling previous knowledge and identifying electrical devices.
Learning Point: Pupils connect previous knowledge to the new topic and are introduced to the concept of different types of current.

Step 2: Presentation of Direct Current (DC)

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines Direct Current (DC) and explains its characteristics using a dry cell or battery as a demonstration. The teacher draws a simple DC waveform on the board and discusses its constant direction and polarity.
Pupils’ Activity: Pupils listen attentively, observe the demonstration, and copy notes from the board. They may ask questions for clarification.
Learning Point: Pupils understand the definition and key characteristics of Direct Current.

Step 3: Presentation of Alternating Current (AC)

Time: 7 minutes
Teaching Skill: Explanation/Visual Aids
Teacher’s Activity: The teacher defines Alternating Current (AC) and explains its characteristics, referring to charts of AC sources (e.g., wall socket). The teacher draws a simple AC sinusoidal waveform on the board, emphasizing its periodic reversal of direction and changing magnitude.
Pupils’ Activity: Pupils listen, observe the charts, and copy notes and the AC waveform from the board.
Learning Point: Pupils understand the definition and key characteristics of Alternating Current.

Step 4: Differences between DC and AC

Time: 8 minutes
Teaching Skill: Comparative Analysis/Discussion
Teacher’s Activity: The teacher leads a discussion comparing DC and AC, highlighting their differences based on direction of flow, polarity, magnitude, and frequency. The teacher uses a table on the board to summarize these differences.
Pupils’ Activity: Pupils actively participate in the discussion, contribute points of difference, and copy the summary table into their notebooks.
Learning Point: Pupils clearly distinguish between Direct Current and Alternating Current based on their fundamental properties.

Step 5: Examples of DC Uses

Time: 4 minutes
Teaching Skill: Illustration/Questioning
Teacher’s Activity: The teacher asks pupils to brainstorm examples of devices or applications that use DC. The teacher then provides additional examples such as batteries, solar cells, and electronic circuits, explaining why DC is preferred in these cases.
Pupils’ Activity: Pupils offer examples and note down the provided examples of DC uses.
Learning Point: Pupils identify practical applications where Direct Current is used.

Step 6: Examples of AC Uses

Time: 4 minutes
Teaching Skill: Illustration/Application
Teacher’s Activity: The teacher asks pupils for examples of devices or applications that use AC, focusing on household power. The teacher expands on these examples, mentioning power outlets, large appliances, and power transmission grids.
Pupils’ Activity: Pupils provide examples and record the examples of AC uses.
Learning Point: Pupils identify practical applications where Alternating Current is used.

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).
State three characteristics of Alternating Current (AC).
Mention two key differences between DC and AC.
List two examples of devices that use DC.

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/Assignment
Teacher’s Activity: The teacher summarizes the main points of the lesson, reiterating the definitions, characteristics, and differences between DC and AC, and their common uses. The teacher then gives an assignment for pupils to research more applications of DC and AC.
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their understanding of the lesson and are encouraged to further explore the topic.

Lesson Keywords

Direct Current (DC) – Electric current that flows in a single, constant direction.
Alternating Current (AC) – Electric current that periodically reverses its direction of flow.
Polarity – The positive and negative terminals of a voltage source.
Frequency – The number of cycles per second for an alternating current, measured in Hertz (Hz).
Waveform – The shape of a wave as plotted on a graph.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to explain why AC is preferred for long-distance power transmission. For pupils needing more support, the teacher will provide simplified diagrams and offer individual attention during activity sessions, focusing on basic definitions and one or two key differences between DC and AC.

Note for teachers using this lesson plan

Ensure that the charts for AC sources and waveforms are clear and visible to all pupils. Real-life examples and demonstrations with dry cells can significantly enhance pupils’ understanding. Encourage active participation and questions to address any misconceptions promptly. Emphasize the safety aspects related to handling electricity.