Earthing, Importance, Methods and Accessories for SS 3

Class: SS 3
Term: First Term
Week: 7
Age: 16-17 years
Duration: 45 minutes
Subject: Basic Electricity
Curriculum Theme: Electrical Safety
Previous Lesson: Electrical Installation Faults, Location and Remedies
Topic: EARTHING
Subject Matter: Importance of earthing: Methods of earthing and Earthing accessories

Specific Objectives

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

Cognitive Domain

• State the importance of earthing in electrical installations.
• List and describe various methods of earthing.
• Identify common earthing accessories.

Psychomotor Domain

• Describe the application of different earthing accessories.
• Differentiate between various earthing methods based on their setup.

Affective Domain

• Appreciate the role of earthing in ensuring electrical safety.
• Show interest in learning about electrical safety measures.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Basic Electricity for Senior Secondary Schools Textbook
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Diagrams illustrating different earthing methods (plate, pipe, rod earthing).
• Samples of earthing accessories such as earthing rod, earthing plate, earthing wire, earthing clamp, and earth continuity conductor.
• A chart showing the symbols for earthing.

Rationale for the Lesson

This lesson is important because it introduces students to earthing, a fundamental safety measure in electrical systems. Understanding earthing helps prevent electric shocks and protects electrical appliances from damage. This knowledge is crucial for anyone working with or around electrical installations.

Prerequisite/Previous Knowledge

Students should have a basic understanding of electric circuits, conductors, insulators, and the general concept of electrical safety.

Lesson Content/Board Summary

EARTHING

Importance of Earthing

Earthing is the process of connecting the non-current carrying metallic parts of an electrical installation to the general mass of the earth. Its importance includes:

1. Protection against electric shock: It provides a safe path for fault current to flow to the earth, preventing dangerous voltages from appearing on exposed metallic parts.
2. Protection of equipment: It protects electrical appliances and equipment from damage due to overcurrents or voltage surges.
3. Stabilisation of voltage: It helps to maintain a stable voltage reference for the electrical system.
4. Discharging lightning current: It provides a path for lightning current to safely dissipate into the earth, protecting structures and equipment.
5. Ensuring proper operation of protective devices: It facilitates the operation of circuit breakers and fuses by providing a low-resistance path for fault currents.

Methods of Earthing

The common methods of earthing include:

1. Plate Earthing: In this method, a copper or galvanised iron (GI) plate is buried vertically in the ground at a depth of at least 3 meters. The earth wire is bolted to the plate. A mixture of charcoal and salt is used around the plate to improve conductivity and keep the soil moist.
2. Pipe Earthing: This is the most common method. A galvanised iron (GI) pipe of suitable diameter and length (usually 2.5 to 4 meters) with holes is buried vertically in the ground. The earth wire is connected to the pipe using a bolt and nut. Charcoal and salt are also used around the pipe to maintain soil moisture and reduce resistance.
3. Rod Earthing: This method uses one or more copper or GI rods driven vertically into the earth. The length of the rod depends on the soil conditions and the required earth resistance. Multiple rods can be connected together to achieve lower resistance. This method is suitable for sandy soil.

Earthing Accessories

Various components are used to achieve effective earthing:

1. Earth Electrode: This is the conductor or group of conductors in direct contact with the earth. Examples include earthing plates, pipes, or rods.
2. Earth Wire (Earthing Conductor): This is the conductor connecting the earth electrode to the main earthing terminal. It is usually green/yellow insulated copper wire.
3. Earthing Clamp: A device used to securely connect the earth wire to the earth electrode or other metallic parts.
4. Earth Continuity Conductor: This conductor connects all the metallic non-current carrying parts of an installation (e.g., appliance casings, conduit pipes) to the main earthing terminal.
5. Main Earthing Terminal: A terminal or bar provided for the connection of the earthing conductor, protective conductors, and equipotential bonding conductors.
6. Test Link: A removable link in the earthing conductor that allows for the disconnection of the earth electrode for testing purposes without disturbing other connections.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Engaging/Questioning

Teacher’s Activity: The teacher begins by asking students about the importance of safety when handling electrical appliances and what happens if a live wire touches the metal casing of an appliance.

Pupils’ Activity: Students share their ideas and experiences related to electrical safety and hazards.

Learning Point: Electrical safety importance

Step 2: Importance of Earthing

Time: 8 minutes

Teaching Skill: Explanation/Discussion

Teacher’s Activity: The teacher explains the concept of earthing and elaborates on its importance, focusing on protection against electric shock and equipment damage. The teacher uses diagrams to illustrate how fault current flows to the earth.

Pupils’ Activity: Students listen attentively, ask questions for clarification, and contribute to the discussion on the benefits of earthing.

Learning Point: Reasons for earthing

Step 3: Methods of Earthing (Plate Earthing)

Time: 7 minutes

Teaching Skill: Explanation/Illustration

Teacher’s Activity: The teacher introduces the first method, Plate Earthing, explaining its setup, the materials used (copper/GI plate, charcoal, salt), and its application. Diagrams are used to show the installation process.

Pupils’ Activity: Students observe the diagrams, take notes, and ask questions about the components and installation of plate earthing.

Learning Point: Plate earthing method

Step 4: Methods of Earthing (Pipe Earthing)

Time: 7 minutes

Teaching Skill: Explanation/Demonstration

Teacher’s Activity: The teacher explains Pipe Earthing, highlighting its common use and describing the installation of the GI pipe, the connection of the earth wire, and the use of charcoal and salt. A sample pipe or diagram is shown.

Pupils’ Activity: Students compare pipe earthing with plate earthing, noting similarities and differences, and engage in a brief discussion.

Learning Point: Pipe earthing method

Step 5: Methods of Earthing (Rod Earthing)

Time: 5 minutes

Teaching Skill: Explanation/Visualisation

Teacher’s Activity: The teacher describes Rod Earthing, explaining how rods are driven into the ground, the materials used, and its suitability for certain soil types. The teacher may show a sample rod.

Pupils’ Activity: Students visualise the process and ask about the factors determining the length and number of rods used.

Learning Point: Rod earthing method

Step 6: Earthing Accessories

Time: 4 minutes

Teaching Skill: Identification/Demonstration

Teacher’s Activity: The teacher presents various earthing accessories (e.g., earth wire, earthing clamp, test link) using actual samples or clear pictures, explaining the function of each accessory in an earthing system.

Pupils’ Activity: Students examine the samples, identify the accessories, and ask questions about their specific uses.

Learning Point: Common earthing accessories

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. What is earthing?
2. State two importance of earthing.
3. Mention two methods of earthing.
4. Name three accessories used in earthing.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Earthing concepts reviewed

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on the importance, methods, and accessories of earthing into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Earthing notes copied

Step 9: Conclusion

Time: 3 minutes

Teaching Skill: Summarising

Teacher’s Activity: The teacher concludes the lesson by reiterating the vital role of earthing in electrical safety and encouraging students to always prioritise safety in electrical installations.

Pupils’ Activity: Students listen and reflect on the importance of the lesson.

Learning Point: Earthing importance reinforced

Continuous Assessment/Further Study

Type: Homework/Practice Exercise

Instruction: Answer the following questions in your notebook:

1. Draw and label a simple diagram illustrating the pipe earthing method.
2. Explain why charcoal and salt are used around earth electrodes.
3. Research and write a short paragraph on the importance of routine testing of earthing systems.

Lesson Keywords

• Earthing – Connecting electrical equipment to the earth to provide a safe path for fault currents.
• Earth Wire – The conductor connecting the earth electrode to the main earthing terminal.
• Earth Electrode – A conductor buried in the earth to provide a connection to the general mass of the earth.
• Plate Earthing – An earthing method using a buried metal plate.
• Pipe Earthing – An earthing method using a buried metal pipe.
• Rod Earthing – An earthing method using metal rods driven into the ground.
• Earthing Clamp – A device for securing earth wire connections.

Differentiation

Support for weaker learners: Provide simplified diagrams and pre-labelled pictures of earthing accessories. Pair them with stronger learners for note-taking and discussion. Focus on identifying the main purpose of earthing and basic accessories.

Extension for faster learners: Encourage them to research different types of soil and their impact on earth resistance, or to investigate the standards and regulations for earthing in Nigeria.

Suggested Lesson Videos

For further visual understanding, search on YouTube for:

• importance of earthing basic electricity SS3
• methods of earthing electrical SS3

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have collected actual samples of earthing accessories or prepared clear, large diagrams. This practical element is key to student understanding. Begin by engaging students with questions about electrical safety to establish relevance. Systematically explain the importance of earthing, followed by each method (plate, pipe, rod earthing), using the visual aids to make the concepts concrete. Allow students to handle the accessories if available, explaining their function. Guide students through the note-taking process after the main concepts have been taught and reviewed. Emphasise the safety aspects throughout the lesson and encourage questions. Pay attention to common misconceptions about electricity flowing to the earth; clarify that it’s about providing a low-resistance path for fault current. Ensure students understand when and why they should copy the Board Summary notes.