Lesson Note on Electric Fields: Meaning, Cells and Series-Parallel Circuits for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: Second Term
Week: 8
Age: 16 years
Duration: 45 minutes
Subject: Physics
Curriculum Theme: Electricity and Magnetism
Previous Lesson: Gravitational Field: Solar System, Kepler’s Laws and Satellites.
Topic: ELECTRIC FIELDS
Subject Matter: Meaning of electric field (region where an electric charge experiences a force), production of continuous charges (primary cells, secondary cells), electric circuit (series arrangement of cells and resistors, parallel arrangement of cells and resistors), resultant e.m.f (determination)

Specific Objectives

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

Cognitive Domain:

• Define an electric field.
• Explain how continuous charges are produced.
• Describe series and parallel arrangements of cells and resistors.
• State the formulas for calculating resultant e.m.f and equivalent resistance.

Affective Domain:

• Appreciate the importance of proper circuit connections.
• Develop an interest in analyzing electrical circuits.

Psychomotor Domain:

• Draw simple circuit diagrams for series and parallel arrangements.
• Calculate the resultant e.m.f for various cell arrangements.
• Calculate the equivalent resistance for various resistor arrangements.

Social Domain:

• Work collaboratively to solve problems related to electric circuits.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• New Concept Physics for Senior Secondary Schools by P.N. Okeke and M.Z. Okeke.
• https://www.physicsclassroom.com/class/circuits/Lesson-4/Series-Circuits
• https://www.electronics-tutorials.ws/dccircuits/dcp_4.html

Instructional Materials

The teacher will teach this lesson with the aid of:

• Charts showing circuit diagrams for series and parallel arrangements of cells and resistors.
• Dry cells.
• Connecting wires.
• Resistors of different values.
• Ammeter and voltmeter (optional for demonstration).

Rationale for the Lesson

This lesson helps pupils understand the fundamental concepts of electric fields and how electrical components are connected to form circuits. It enables them to calculate total voltage and resistance in different circuit configurations, which is important for understanding how electrical devices work in homes and industries.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of electric charge, electric current, voltage, and resistance.

Lesson Content/Board Summary

ELECTRIC FIELDS AND CIRCUITS

Meaning of Electric Field

An electric field is defined as the region or space around an electric charge where another electric charge would experience an electrostatic force. Electric fields are represented by electric field lines which originate from positive charges and terminate on negative charges.

Production of Continuous Charges (Sources of e.m.f)

Continuous flow of charge (current) in a circuit requires a continuous source of electromotive force (e.m.f). This is produced by converting other forms of energy into electrical energy.

• Primary Cells: These are non-rechargeable cells that convert chemical energy into electrical energy. Examples include dry cells (Leclanché cell) and Daniel cells.
• Secondary Cells: These are rechargeable cells that can convert chemical energy into electrical energy and vice-versa. They can be recharged by passing current through them in the opposite direction. Examples include lead-acid accumulators (car batteries) and nickel-cadmium batteries.

Electric Circuit

An electric circuit is a complete path through which electric current flows. A simple electric circuit consists of a source of e.m.f (like a cell), conducting wires, and components (like resistors, switches, bulbs).

Arrangement of Cells in Series and Parallel

Series Arrangement of Cells

In a series arrangement, cells are connected end-to-end such that the positive terminal of one cell is connected to the negative terminal of the next cell. This arrangement increases the total voltage.

Resultant e.m.f (E_total):

• If cells are connected assisting each other (positive to negative):
  E_total = E₁ + E₂ + … + E_n
• If cells are connected opposing each other:
  E_total = |E₁ – E₂| (for two cells)

Parallel Arrangement of Cells

In a parallel arrangement, cells are connected across the same two points, with all positive terminals connected together and all negative terminals connected together. This arrangement increases the current capacity but keeps the voltage the same (if identical cells are used).

Resultant e.m.f (E_total):

• If identical cells are connected in parallel:
  E_total = E (where E is the e.m.f of a single cell).

Arrangement of Resistors in Series and Parallel

Series Arrangement of Resistors

In a series arrangement, resistors are connected end-to-end, forming a single path for current. The total resistance is the sum of individual resistances.

Equivalent Resistance (R_total):
R_total = R₁ + R₂ + … + R_n

Parallel Arrangement of Resistors

In a parallel arrangement, resistors are connected across the same two points, providing multiple paths for current. The reciprocal of the total resistance is the sum of the reciprocals of individual resistances.

Equivalent Resistance (R_total):
1/R_total = 1/R₁ + 1/R₂ + … + 1/R_n

Worked Examples

Example 1 (Cells):
Three cells, each with an e.m.f of 1.5 V, are connected in series. What is the resultant e.m.f?

Step 1: Identify the connection type.
The cells are connected in series.

Step 2: Apply the formula for series connection.
E_total = E₁ + E₂ + E₃

Step 3: Substitute values and calculate.
E_total = 1.5 V + 1.5 V + 1.5 V = 4.5 V

The resultant e.m.f is 4.5 V.

Example 2 (Resistors):
Two resistors, 6 Ω and 3 Ω, are connected in parallel. Calculate their equivalent resistance.

Step 1: Identify the connection type.
The resistors are connected in parallel.

Step 2: Apply the formula for parallel connection.
1/R_total = 1/R₁ + 1/R₂

Step 3: Substitute values.
1/R_total = 1/6 + 1/3

Step 4: Find a common denominator and add.
1/R_total = 1/6 + 2/6 = 3/6 = 1/2

Step 5: Invert to find R_total.
R_total = 2 Ω

The equivalent resistance is 2 Ω.

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 asks pupils what makes a torchlight work and how batteries are put into devices.
Pupils’ Activity: Pupils respond by mentioning batteries and how they are inserted.
Learning Point: Pupils are introduced to the concept of electrical power sources and connections.

Step 2: Meaning of Electric Field

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher defines an electric field as a region where a charge experiences a force.
Pupils’ Activity: Pupils listen attentively and copy the definition.
Learning Point: Pupils understand the definition of an electric field.

Step 3: Production of Continuous Charges

Time: 5 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains primary and secondary cells as sources of continuous charges, giving examples.
Pupils’ Activity: Pupils listen and note down the types and examples of cells.
Learning Point: Pupils identify different sources of continuous charges.

Step 4: Electric Circuit

Time: 5 minutes
Teaching Skill: Definition/Listing
Teacher’s Activity: The teacher defines an electric circuit and lists its basic components.
Pupils’ Activity: Pupils define an electric circuit and list its components.
Learning Point: Pupils understand what an electric circuit is and its parts.

Step 5: Arrangement of Cells and Resistors in Series

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher draws circuit diagrams for cells and resistors in series, explains the connections, states the formulas for resultant e.m.f and equivalent resistance, and solves a worked example on the board.
Pupils’ Activity: Pupils observe the diagrams, copy notes, and participate in solving the example.
Learning Point: Pupils learn how to connect cells and resistors in series and calculate their total values.

Step 6: Arrangement of Cells and Resistors in Parallel

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher draws circuit diagrams for cells and resistors in parallel, explains the connections, states the formulas for resultant e.m.f and equivalent resistance, and solves a worked example on the board.
Pupils’ Activity: Pupils observe the diagrams, copy notes, and participate in solving the example.
Learning Point: Pupils learn how to connect cells and resistors in parallel and calculate their total values.

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. Define an electric field.
2. Mention two types of cells that produce continuous charges.
3. State the formula for the total e.m.f of three cells, E₁, E₂, and E₃, connected in series.
4. Calculate the equivalent resistance of two resistors, 10 Ω and 15 Ω, connected in parallel.

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
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework, which includes drawing circuit diagrams for various arrangements and solving calculation problems.
Pupils’ Activity: Pupils ask questions for clarification and copy the homework.
Learning Point: Pupils reinforce their understanding and apply knowledge to new problems.

Lesson Keywords

• Electric Field – A region where a charged particle experiences an electric force.
• Primary Cell – A non-rechargeable cell that converts chemical energy to electrical energy.
• Secondary Cell – A rechargeable cell that converts chemical energy to electrical energy and vice-versa.
• Electric Circuit – A complete path for electric current flow.
• Series Connection – Components connected end-to-end along a single path.
• Parallel Connection – Components connected across the same two points, providing multiple paths.
• Resultant e.m.f – The total electromotive force in a circuit or arrangement of cells.
• Equivalent Resistance – The single resistance that can replace a combination of resistors without changing the circuit’s total current and voltage.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide more complex circuit problems involving combinations of series and parallel arrangements. For pupils needing more support, the teacher can provide simplified diagrams, step-by-step guides for calculations, and peer tutoring opportunities.

Note for teachers using this lesson plan

Ensure that all diagrams drawn on the board are clear and well-labeled. Encourage pupils to draw their own diagrams accurately. Provide practical examples of series and parallel circuits from everyday life to make the lesson relatable. Emphasize the units for e.m.f (Volts) and resistance (Ohms) in all calculations.