Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: First Term
Week: 5
Age: 15 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Technology
Previous Lesson: Measuring: Types and Uses of Measuring Instruments.
Topic: PRACTICAL CLASS ON HOW TO USE MEASURING INSTRUMENTS
Subject Matter: Identifying an ohmmeter, setting the meter to ohms, measuring continuity, interpreting continuity readings, safe handling of measuring instruments.

Specific Objectives

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

Cognitive Domain:

Identify an ohmmeter.
Explain the steps for setting an ohmmeter to measure ohms.
Describe how to interpret continuity readings.

Affective Domain:

Appreciate the importance of safe handling of measuring instruments.
Value accuracy when taking measurements in electrical work.

Psychomotor Domain:

Demonstrate how to set an ohmmeter to the appropriate range.
Carry out continuity measurements on simple circuits or wires.
Handle measuring instruments safely during practical work.

Collaborate with peers during practical activities.
Communicate findings clearly during practical demonstrations.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Electrical Installation and Maintenance Work.
State Unified Scheme of Work for Senior Secondary Schools.
Electrical Installation and Maintenance Work for Senior Secondary Schools by N.O. Okoro.
https://www.electricaltechnology.org/2020/09/how-to-use-ohmmeter.html

Instructional Materials

The teacher will teach this lesson with the aid of:

Ohmmeter (analogue and digital).
Continuity practice wires.
Sample circuits (e.g., a simple series circuit with a bulb).
Whiteboard/Chalkboard and markers/chalk.

Rationale for the Lesson

This lesson helps pupils develop practical skills in using essential electrical measuring instruments. Understanding how to use an ohmmeter to check continuity is important for fault finding and ensuring proper electrical connections, which are valuable skills in daily life and future careers in electrical work.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of electrical circuits and the concept of resistance from previous lessons.

Lesson Content/Board Summary

PRACTICAL CLASS ON THE USE OF OHMMETER FOR CONTINUITY MEASUREMENT

Identification of an Ohmmeter

An ohmmeter is an electrical measuring instrument used to measure electrical resistance in ohms. It can be analogue (with a needle and scale) or digital (with a numerical display).

Setting the Ohmmeter to Ohms

Before taking a measurement, the ohmmeter must be set to the correct function and range.

The following are steps to set an ohmmeter:

Select the ‘Ohms’ (Ω) function on the meter.
Choose an appropriate resistance range (e.g., x1, x10, 200Ω, 2kΩ). Start with a higher range if the resistance is unknown.
For analogue meters, zero the meter by touching the probes together and adjusting the ‘zero adjust’ knob.

Measuring Continuity with an Ohmmeter

Continuity refers to whether an electrical path is complete or broken. An ohmmeter is used to check if a wire or component has a continuous path for current to flow.

The following are steps to measure continuity:

Ensure the circuit or component is de-energized (no power supply).
Set the ohmmeter to the continuity test function (often indicated by a buzzer symbol) or a low resistance range (e.g., 200Ω).
Touch the meter probes to each end of the wire or component being tested.

Interpreting Continuity Readings

The reading on the ohmmeter indicates the state of continuity.

The following are ways to interpret continuity readings:

Good Continuity: A very low resistance reading (close to 0 ohms) or a audible beep (on meters with a buzzer) indicates a continuous path.
No Continuity (Open Circuit): A very high resistance reading (infinity, or ‘OL’ on digital meters) indicates a broken path.
High Resistance: A significantly higher resistance than expected may indicate a poor connection or a partially faulty component.

Safe Handling of Measuring Instruments

Proper handling of measuring instruments is important to prevent damage to the instrument and ensure safety.

The following are safety rules for handling measuring instruments:

Always ensure the circuit is de-energized before taking resistance or continuity measurements.
Hold the probes by the insulated parts.
Do not drop the instruments.
Store instruments in their protective cases after use.
Never use an ohmmeter to measure resistance in a live circuit, as this can damage the meter.

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, reviews the previous lesson briefly, and introduces the topic by asking pupils if they know how electricians check if a wire is broken or connected. The teacher then displays an ohmmeter and explains that today’s lesson is a practical class on using it to measure continuity.
Pupils’ Activity: Pupils respond to questions and observe the displayed instruments.
Learning Point: Pupils are introduced to the topic and relate it to real-world scenarios.

Step 2: Identification of an Ohmmeter

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher displays various types of ohmmeters (analogue and digital) and explains their parts, functions, and symbols. The teacher allows pupils to handle the instruments carefully.
Pupils’ Activity: Pupils observe, listen, and carefully handle the ohmmeters as instructed.
Learning Point: Pupils can identify an ohmmeter and its basic features.

Step 3: Setting the Ohmmeter to Ohms

Time: 7 minutes
Teaching Skill: Demonstration/Guidance
Teacher’s Activity: The teacher demonstrates how to set an ohmmeter to the resistance (ohms) function and select an appropriate range. The teacher also shows how to zero an analogue meter. Pupils are guided to practice setting the meters.
Pupils’ Activity: Pupils observe the demonstration and practice setting the ohmmeter under the teacher’s guidance.
Learning Point: Pupils can correctly set an ohmmeter for resistance measurement.

Step 4: Measuring Continuity with an Ohmmeter

Time: 8 minutes
Teaching Skill: Practical Demonstration
Teacher’s Activity: The teacher demonstrates how to measure continuity on practice wires and simple circuits. The teacher emphasizes ensuring the circuit is de-energized before testing. Pupils are then given practice wires and circuits to measure continuity in groups.
Pupils’ Activity: Pupils observe the demonstration and, in groups, practice measuring continuity on provided materials.
Learning Point: Pupils acquire the practical skill of measuring continuity.

Step 5: Interpreting Continuity Readings

Time: 7 minutes
Teaching Skill: Explanation/Interpretation
Teacher’s Activity: The teacher explains how to interpret the readings obtained from the ohmmeter (low resistance/beep for good continuity, high resistance/OL for no continuity). The teacher uses examples from the practical session.
Pupils’ Activity: Pupils listen, ask questions, and relate the explanation to their practical readings.
Learning Point: Pupils can correctly interpret continuity readings.

Step 6: Safe Handling of Measuring Instruments

Time: 6 minutes
Teaching Skill: Instruction/Emphasis
Teacher’s Activity: The teacher discusses the importance of safe handling of measuring instruments, listing rules such as ensuring circuits are de-energized, holding probes by insulation, and proper storage.
Pupils’ Activity: Pupils listen and note the safety rules.
Learning Point: Pupils understand and appreciate the safety precautions for using measuring instruments.

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 an ohmmeter used for?
State two steps for setting an ohmmeter to measure continuity.
How do you interpret a reading of ‘OL’ or infinity on an ohmmeter when checking continuity?
Mention two safety precautions to observe when using an ohmmeter.

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 key points of the lesson, reiterating the importance of practical skills in electrical work and the need for safety. The teacher assigns homework: “Draw and label an ohmmeter (either analogue or digital).”
Pupils’ Activity: Pupils listen attentively and copy the homework.
Learning Point: Pupils consolidate their understanding and receive an assignment.

Lesson Keywords

Ohmmeter – An instrument used to measure electrical resistance.
Continuity – The presence of a complete path for current flow in a circuit or wire.
Ohms (Ω) – The unit of measurement for electrical resistance.
Resistance – The opposition to the flow of electric current.
De-energized – Switched off; having no electrical power supply.

Differentiation

For pupils who grasp the concepts quickly, the teacher can challenge them to identify different types of faults (e.g., short circuits, open circuits) using the ohmmeter. For pupils needing more support, the teacher will provide closer supervision during practical sessions and offer simplified step-by-step instructions.

Note for teachers using this lesson plan

Ensure that all measuring instruments are in good working condition and that there are enough instruments for pupils to practice effectively in small groups. Emphasize safety throughout the practical session. Encourage hands-on participation from all pupils. Provide clear, simple instructions for each practical step.