Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: 1st Term
Week: 3
Age: 16 years
Duration: 45 minutes
Subject: Basic Electricity
Curriculum Theme: Electrical Energy and Power Distribution
Previous Lesson: Electricity Generation: Gas, Steam and Thermal Power Stations.
Topic: TRANSMISSION OF ELECTRICITY
Subject Matter: Meaning of transmission of electricity (sending power over long distances), method of transmission of electricity (high voltage transfer), parts of national grid (power stations, transmission lines, substations), differences between short and medium transmission lines (distance and voltage levels).

Specific Objectives

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

Cognitive Domain:

Define transmission of electricity.
Explain the method of electricity transmission.
Identify the main parts of the national grid.
State the differences between short and medium transmission lines.

Affective Domain:

Appreciate the importance of efficient electricity transmission.
Show interest in how electricity reaches consumers.

Psychomotor Domain:

Draw a simple diagram illustrating a basic transmission line.
Point out components of the national grid on a diagram.

Discuss the socio-economic impact of reliable electricity transmission.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
NELSON: Comprehensive Certificate Physics for Senior Secondary Schools.
Any relevant Basic Electricity textbook for Senior Secondary Schools.

Instructional Materials

The teacher will teach this lesson with the aid of:

Pictures showing parts of the national grid.
Charts illustrating electricity transmission.
Diagrams of transmission lines and substations.

Rationale for the Lesson

This lesson helps pupils understand how electricity generated at power stations is delivered to homes and industries over long distances. It enables pupils to appreciate the system that ensures power availability and the reasons behind specific transmission methods.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of electricity generation, basic electrical circuits, voltage, and current.

Lesson Content/Board Summary

TRANSMISSION OF ELECTRICITY

Meaning of Transmission of Electricity

Transmission of electricity is the bulk transfer of electrical energy from generating power stations to electrical substations located near demand centers. This process involves sending electrical power over long distances through a network of transmission lines.

Method of Transmission of Electricity (High Voltage Transfer)

Electricity is transmitted using very high voltages (e.g., 132kV, 330kV) to minimize energy loss during transmission. At the power station, step-up transformers increase the generated voltage to high levels. This reduces the current (I) for a given power (P = VI). Since power loss in transmission lines is proportional to the square of the current (P_loss = I²R), reducing the current significantly decreases power loss, making transmission more efficient.

Parts of the National Grid

The national grid is a network of interconnected power stations, transmission lines, and substations that ensures electricity is available across a country. Its main parts are:

Power Stations: Facilities where electricity is generated (e.g., thermal, hydro, solar).
Step-up Substations: Located at power stations, they increase the voltage of the generated electricity for efficient long-distance transmission.
Transmission Lines: High-voltage cables, typically mounted on tall pylons, that carry electricity over long distances from power stations to substations.
Step-down Substations: Located near consumption areas, these reduce the high transmission voltage to lower levels suitable for distribution to consumers.
Distribution Lines: Lower voltage lines that carry electricity from step-down substations to individual homes and businesses.

Differences between Short and Medium Transmission Lines

Transmission lines are categorized based on their length and the voltage levels they carry:

Short Transmission Lines:
- Distance: Typically less than 80 kilometers (50 miles).
- Voltage Levels: Usually operate at voltages below 20 kV.
- Characteristics: Line capacitance is often neglected in analysis due to short length.
Medium Transmission Lines:
- Distance: Typically range from 80 kilometers to 250 kilometers (50 to 150 miles).
- Voltage Levels: Operate at voltages between 20 kV and 100 kV.
- Characteristics: Line capacitance is considered and modeled using methods like the nominal T or nominal Pi methods.

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 how they think electricity gets from power stations to their homes.
Pupils’ Activity: Pupils respond by sharing their ideas, leading to the topic of electricity transmission.
Learning Point: Pupils are introduced to the concept of electricity transmission and its importance.

Step 2: Meaning of Transmission of Electricity

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines transmission of electricity as the bulk transfer of electrical energy over long distances and explains its purpose.
Pupils’ Activity: Pupils listen attentively and copy the definition into their notebooks.
Learning Point: Pupils understand the definition and purpose of electricity transmission.

Step 3: Method of Transmission of Electricity

Time: 7 minutes
Teaching Skill: Explanation/Justification
Teacher’s Activity: The teacher explains that electricity is transmitted at high voltages and justifies why this method is used (to minimize power loss).
Pupils’ Activity: Pupils listen and ask questions for clarification, explaining why high voltage is used.
Learning Point: Pupils understand the high voltage transmission method and its efficiency benefits.

Step 4: Parts of the National Grid

Time: 8 minutes
Teaching Skill: Illustration/Identification
Teacher’s Activity: The teacher displays pictures and diagrams of the national grid, pointing out and explaining its main components: power stations, transmission lines, and substations.
Pupils’ Activity: Pupils observe the pictures, identify the parts, and note their functions.
Learning Point: Pupils can identify and describe the components of the national grid.

Step 5: Differences between Short and Medium Transmission Lines

Time: 8 minutes
Teaching Skill: Comparison/Differentiation
Teacher’s Activity: The teacher explains the differences between short and medium transmission lines based on distance and voltage levels, using examples.
Pupils’ Activity: Pupils listen, ask questions, and state the key differences between the two types of lines.
Learning Point: Pupils can differentiate between short and medium transmission lines.

Step 6: Discussion and Clarification

Time: 5 minutes
Teaching Skill: Questioning/Feedback
Teacher’s Activity: The teacher facilitates a brief discussion to address any remaining questions and clarify misconceptions.
Pupils’ Activity: Pupils participate in the discussion and seek further clarification.
Learning Point: Pupils consolidate their understanding and clarify doubts.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is meant by the transmission of electricity?
State one reason why electricity is transmitted at high voltages.
List three main parts of the national grid.
Mention two differences between short and medium transmission lines.

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 key points of the lesson and assigns homework: “Draw a simple diagram showing the path of electricity from a power station to a consumer, labeling the main components.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils review the lesson and prepare for further learning.

Lesson Keywords

Transmission – The process of sending electrical energy over long distances.
National Grid – A network of power stations, transmission lines, and substations.
High Voltage – A very large electrical potential difference used for efficient power transfer.
Substation – A facility that transforms voltage levels for transmission or distribution.
Power Station – A place where electricity is generated.
Transmission Line – Cables that carry high-voltage electricity between power stations and substations.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research the types of conductors used in transmission lines and their properties. For pupils needing more support, the teacher will provide simplified diagrams and allow for peer-tutoring and additional explanations.

Note for teachers using this lesson plan

Teachers should ensure that visual aids are clear and relevant to the Nigerian context. Emphasize the practical implications of efficient electricity transmission on daily life. Encourage pupils to ask questions and relate the concepts to their experiences with electricity.