Lesson Plan | Traditional Methodology | Electricity: Electric Field

Objectives

Duration: 10 to 15 minutes

The purpose of this stage is to provide a clear and detailed view of the objectives that students should achieve by the end of the lesson. This will help guide the teacher's explanation and ensure that all necessary skills are effectively covered, providing a solid foundation for understanding the electric field.

Main Objectives

1. Relate the electric field generated to the electric force.

2. Calculate the electric field generated by a given charge.

3. Verify the magnitude, direction, and sense of an electric field.

Introduction

Duration: 10 to 15 minutes

The purpose of this stage is to create a solid foundation for the students by contextualizing the topic and showing its practical relevance. This helps arouse the interest and curiosity of the students, facilitating their understanding of the concepts that will be covered throughout the lesson.

Context

To start the lesson on Electric Field, it is important to place students in the context of electric forces that they already know. Explain that, just as gravitational force acts at a distance between two bodies with mass, electric force acts between charged particles. Mention that the idea of electric field helps us understand how these forces are transmitted through space, even without direct contact between the charges.

Curiosities

Did you know that the concept of electric field is fundamental for the operation of many modern technologies? For example, it is essential for the operation of magnetic resonance imaging devices used in hospitals for medical diagnostics. Moreover, the electric field is a basic principle in capacitors, components that store electrical energy and are used in virtually all electronic devices, from cell phones to computers.

Development

Duration: 55 to 60 minutes

The purpose of this stage is to provide a detailed and practical understanding of electric field concepts, preparing students to apply these concepts to real-world problems. By covering various topics and solving practical questions, students will be able to relate the electric field to electric force, calculate electric fields generated by different charges, and determine the characteristics of the electric field, such as magnitude, direction, and sense.

Covered Topics

1. Concept of Electric Field: Explain that the electric field is a region of space where an electric charge experiences a force. Relate the electric force (F) to the electric field (E) through the formula: F = qE, where q is the charge. 2. Electric Field Lines: Detail that electric field lines are imaginary lines that represent the direction of the electric field. Explain that lines emanate from positive charges and enter negative charges, and they never cross. 3. Electric Field of a Point Charge: Present the formula for the electric field generated by a point charge: E = k * |Q| / r², where k is the electrostatic constant, Q is the charge, and r is the distance from the charge. Show calculation examples. 4. Superposition of Electric Fields: Explain that the resulting electric field at a point due to multiple charges is the vector sum of the individual electric fields. Provide practical examples. 5. Magnitude, Direction, and Sense of the Electric Field: Show how to determine the magnitude, direction, and sense of the electric field in different situations, emphasizing the importance of understanding these characteristics for solving problems.

Classroom Questions

1. Calculate the electric field at a distance of 0.5 m from a charge of +3 μC. 2. Draw the electric field lines for two equal and opposite charges (+Q and -Q) separated by a distance d. 3. Determine the resulting electric field at a point P that is equidistant from two equal charges of +2 μC, separated by a distance of 1 m.

Questions Discussion

Duration: 15 to 20 minutes

The purpose of this stage is to consolidate the knowledge acquired by students through detailed discussion of the solved questions, promoting a collaborative and interactive learning environment. This moment allows students to clarify doubts, reinforce concepts, and share their own reflections, enhancing the understanding and retention of the content addressed.

Discussion

•  Question 1: Calculate the electric field at a distance of 0.5 m from a charge of +3 μC.

Explanation: The formula for the electric field of a point charge is E = k * |Q| / r². Using k = 8.99 x 10⁹ N·m²/C², Q = 3 x 10⁻⁶ C, and r = 0.5 m:

E = (8.99 x 10⁹) * (3 x 10⁻⁶) / (0.5)²

E = (8.99 x 10⁹) * (3 x 10⁻⁶) / 0.25

E = (8.99 x 10⁹) * 12 x 10⁻⁶

E = 107.88 x 10³ N/C

The electric field at 0.5 m from a charge of +3 μC is 107.88 x 10³ N/C.

•  Question 2: Draw the electric field lines for two equal and opposite charges (+Q and -Q) separated by a distance d.

Explanation: The electric field lines emanate from the positive charge and enter the negative charge. In the middle of the path between the two charges, the lines are denser, indicating a stronger electric field. The field lines never cross and form a symmetrical pattern around the charges.

•  Question 3: Determine the resulting electric field at a point P that is equidistant from two equal charges of +2 μC, separated by a distance of 1 m.

Explanation: Since the charges are equal and of the same sign, the electric fields generated by each charge at P will have the same magnitude but opposite direction. Thus, the horizontal components of the fields cancel out, and the vertical components add up.

E_total = 2 * (E * cos(45°))

Using E = k * |Q| / r² with Q = 2 x 10⁻⁶ C and r = 0.5 m (half the distance between the charges):

E = (8.99 x 10⁹) * (2 x 10⁻⁶) / (0.5)²

E = (8.99 x 10⁹) * (2 x 10⁻⁶) / 0.25

E = (8.99 x 10⁹) * 8 x 10⁻⁶

E = 71.92 x 10³ N/C

Then, E_total = 2 * (71.92 x 10³) * (√2 / 2) = 101.66 x 10³ N/C

The resulting electric field at point P is 101.66 x 10³ N/C.

Student Engagement

1.  Question 1: How can the concept of electric field be applied in technologies we use in everyday life? Provide specific examples. 2.  Question 2: Consider two equal positive charges arranged along a horizontal axis. How would the behavior of the electric field lines be between them and around? 3.  Question 3: If we place a third negative charge at point P between two positive charges, how would that affect the resulting electric field at that point? 4.  Reflection: How can understanding the electric field help solve problems in other areas of physics and engineering?

Conclusion

Duration: 10 to 15 minutes

The purpose of this stage is to consolidate students' learning by recapping the main points covered in the lesson and reinforcing the connection between theory and practice. Furthermore, highlighting the relevance of the topic to daily life helps motivate students to delve deeper into the subject and see the importance of the acquired knowledge.

Summary

• The electric field is a region of space where an electric charge experiences a force.
• The relationship between electric force (F) and electric field (E) is given by the formula F = qE.
• Electric field lines emanate from positive charges and enter negative charges.
• The formula for the electric field of a point charge is E = k * |Q| / r².
• The resulting electric field due to multiple charges is the vector sum of the individual fields.
• Determining the magnitude, direction, and sense of the electric field is crucial for solving problems.

Throughout the lesson, the theoretical concepts of the electric field were connected to practice through detailed examples and problem-solving. This allowed students to visualize the application of concepts in real situations and experience the practical resolution of electric field calculations.

Understanding the electric field is fundamental for various technologies we use daily, such as capacitors in electronic devices and magnetic resonance imaging equipment in hospitals. Understanding this concept allows for innovation and maintenance of essential technologies for our modern life.