Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 1st Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Basic Electricity
Curriculum Theme: Basic Electricity
Previous Lesson: Ohm’s Law.
Topic: ELECTRIC POWER
Subject Matter: Definition of electric power, symbol and unit of electric power, relationship between power voltage and current, calculation of power using P equals V I, alternative power formulae in simple form

Specific Objectives

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

Cognitive Domain:

Define electric power.
State the symbol and unit of electric power.
State the relationship between power, voltage, and current.
Recall alternative power formulae (P = I²R, P = V²/R).

Affective Domain:

Appreciate the importance of understanding electric power in daily applications.
Develop an interest in solving problems related to electric power.

Psychomotor Domain:

Calculate electric power in a circuit using P = VI.
Solve simple problems involving alternative power formulae.

Participate actively in class discussions on electric power.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Education Curriculum
State Unified Scheme of Work
New System Physics for Senior Secondary Schools by P.N. Okeke and C.N. Anyakoha
https://www.physicsclassroom.com/class/circuits/Lesson-2/Electric-Power
https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/a/electric-power

Instructional Materials

The teacher will teach this lesson with the aid of:

Circuit diagrams
Sample circuit components (e.g., bulb, resistor)
Charts displaying power formulae

Rationale for the Lesson

Understanding electric power helps pupils to know how electrical appliances work and how much energy they consume. This knowledge is important for managing electricity usage in homes and industries, making it relevant to their daily lives.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of basic electrical concepts such as current, voltage, resistance, and Ohm’s Law.

Lesson Content/Board Summary

ELECTRIC POWER

Definition of Electric Power

Electric power is the rate at which electrical energy is converted into another form of energy (e.g., heat, light, mechanical energy) in an electric circuit. It is also defined as the rate at which work is done by an electric current.

Symbol and Unit of Electric Power

The symbol for electric power is ‘P’. The standard unit of electric power is the Watt (W). One Watt is defined as one Joule per second (1 W = 1 J/s).

Relationship between Power, Voltage, and Current

Electric power (P) is directly proportional to both the voltage (V) across a component and the current (I) flowing through it. This relationship is expressed by the formula:

P = V × I

Where:

P = Power in Watts (W)
V = Voltage in Volts (V)
I = Current in Amperes (A)

Calculation of Power using P = VI

To calculate electric power using P = VI, multiply the voltage supplied to the circuit or component by the current flowing through it.

Example: Calculate the power consumed by an electric heater that draws a current of 5 A when connected to a 220 V supply.

Solution:
Given: V = 220 V, I = 5 A
Using P = V × I
P = 220 V × 5 A
P = 1100 W

Therefore, the power consumed is 1100 Watts.

Alternative Power Formulae

Besides P = VI, electric power can also be calculated using other formulae derived from Ohm’s Law (V = IR).

The alternative formulae for electric power are:

P = I²R (Power equals current squared times resistance)
P = V²/R (Power equals voltage squared divided by resistance)

Where:

P = Power in Watts (W)
I = Current in Amperes (A)
R = Resistance in Ohms (Ω)
V = Voltage in Volts (V)

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 questions related to the previous lesson on Ohm’s Law and basic electrical quantities like voltage and current. The teacher then asks pupils what they observe about the brightness of different bulbs or the heat produced by different heaters.
Pupils’ Activity: Pupils respond to questions and share their observations.
Learning Point: Pupils recall previous knowledge and are introduced to the concept of electrical work/energy.

Step 2: Presentation of Topic and Objectives

Time: 2 minutes
Teaching Skill: Explaining
Teacher’s Activity: The teacher introduces the topic “ELECTRIC POWER” and states the lesson objectives to the pupils.
Pupils’ Activity: Pupils listen attentively and note down the topic and objectives.
Learning Point: Pupils know what they are expected to learn during the lesson.

Step 3: Definition of Electric Power

Time: 6 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines electric power as the rate at which electrical energy is converted or work is done by an electric current, providing simple analogies.
Pupils’ Activity: Pupils listen, ask questions for clarification, and write down the definition.
Learning Point: Pupils understand the meaning of electric power.

Step 4: Symbol and Unit of Electric Power

Time: 5 minutes
Teaching Skill: Naming/Stating
Teacher’s Activity: The teacher states the symbol for electric power (P) and its standard unit, the Watt (W), explaining that 1 Watt equals 1 Joule per second.
Pupils’ Activity: Pupils identify the symbol and unit of electric power and write them down.
Learning Point: Pupils can identify and state the symbol and unit of electric power.

Step 5: Relationship and P = VI Formula

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the relationship between power, voltage, and current, presenting the formula P = VI. The teacher then works through a sample calculation on the board using the provided example from the lesson content.
Pupils’ Activity: Pupils observe the demonstration, copy the formula, and solve the example problem.
Learning Point: Pupils understand how to calculate electric power using voltage and current.

Step 6: Alternative Power Formulae

Time: 7 minutes
Teaching Skill: Derivation/Listing
Teacher’s Activity: The teacher presents the alternative formulae for electric power (P = I²R and P = V²/R) and briefly explains how they are derived from Ohm’s Law. The teacher displays a chart showing these formulae.
Pupils’ Activity: Pupils listen, copy the formulae, and ask questions about their application.
Learning Point: Pupils can identify and recall alternative formulae for electric power.

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 electric power.
State the symbol and unit of electric power.
State the relationship between power, voltage, and current.
Mention two alternative formulae for calculating electric power.
Calculate the power consumed by an appliance that draws 2A from a 220V supply.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarizing
Teacher’s Activity: The teacher summarizes the main points of the lesson, reiterating the definition, units, and formulae for electric power. The teacher then gives pupils homework to practice calculations.
Pupils’ Activity: Pupils listen and copy the homework assignment.
Learning Point: Pupils consolidate their understanding of electric power.

Lesson Keywords

Power – The rate at which electrical energy is converted or work is done.
Watt (W) – The standard unit of electric power.
Voltage (V) – The electric potential difference between two points in a circuit.
Current (I) – The flow of electric charge.
Resistance (R) – The opposition to the flow of electric current.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide more complex problems involving combined circuits. For pupils needing extra support, the teacher will provide simplified examples and one-on-one guidance, focusing on the basic P = VI formula and its direct application.

Note for teachers using this lesson plan

Ensure pupils have a solid understanding of Ohm’s Law before introducing electric power formulae. Encourage pupils to always state the units in their calculations. Use real-life examples of appliances and their power ratings to make the lesson more relatable.