Lesson Plan | Traditional Methodology | Magnetism: Force on Current-Carrying Wire
| Keywords | Magnetic Force, Wire with Electric Current, Biot-Savart Law, Right-Hand Rule, Magnetic Field, Electric Current, Practical Problems, Formula F = I × L × B × sin(θ), Student Engagement, Everyday Technologies |
| Required Materials | Whiteboard and markers, Projector or TV to display slides, Presentation slides, Notebook and pen for each student, Examples of practical problems, Illustrative diagrams, Ruler and protractor to measure angles in the diagrams, Calculators |
Objectives
Duration: 10 - 15 minutes
The purpose of this stage is to introduce students to the concept of magnetic force acting on wires with electric current. By providing an overview of the lesson's objectives, students will be better prepared to understand and apply the physics concepts presented. This stage establishes a solid foundation for detailed understanding and practical application of subsequent topics.
Main Objectives
1. Explain the concept of magnetic force in wires with electric current.
2. Demonstrate how to calculate the magnetic force using Biot-Savart's Law and the right-hand rule.
3. Solve practical problems involving the calculation of magnetic forces in wires with electric current.
Introduction
Duration: 10 - 15 minutes
Purpose
The purpose of this stage is to contextualize and engage students with the theme of magnetic force in wires with electric current. By providing interesting and relevant information, students will be more motivated and prepared to dive into the physical concepts that will be addressed in the lesson. This introduction aims to spark curiosity and establish a connection between academic content and the real world.
Context
Initial Context
Start the lesson by explaining the concept of magnetism and its relationship to electricity. Use everyday examples, such as the operation of electric motors and speakers, which rely on magnetism to function. Briefly describe how electric current can generate a magnetic field around a wire, introducing the idea that magnetic forces can act on wires carrying electric current. This is a fundamental phenomenon behind many modern technologies that students use daily, such as smartphones and computers.
Example: "Have you ever wondered how the speakers in your phones can produce sound? This happens thanks to the interaction between electric currents and magnetic fields!"
Curiosities
Curiosity
The Earth is a giant natural magnet! The Earth's magnetic field protects our planet from solar winds and is essential for life on Earth. This same principle of magnetism is used in compasses, which always point north, helping navigation for centuries.
Development
Duration: 40 - 50 minutes
Purpose
The purpose of this stage is to provide students with a detailed and practical understanding of the magnetic force in wires with electric current. By explaining the fundamental concepts and applying these concepts to practical problems, students will be able to calculate and predict magnetic forces in different situations. This stage also aims to consolidate theoretical knowledge through practical examples and application questions, ensuring that students can effectively use the formulas and rules.
Covered Topics
1. Magnetic Force in Wires with Electric Current
Explain that the magnetic force acting on a wire with electric current is given by the formula F = I × L × B × sin(θ), where: F is the magnetic force I is the electric current L is the length of the wire B is the magnetic field θ is the angle between the wire and the magnetic field
Detail each of these components and how they influence the resultant force. Provide practical examples and use diagrams to illustrate the orientation of the wire concerning the magnetic field. 2. Biot-Savart Law
Describe the Biot-Savart Law, which explains how electric current creates a magnetic field around a wire. The formula is B = (μ₀ / 4π) × (I × dl × sin(θ) / r²). Explain each term of the formula: B is the magnetic field μ₀ is the magnetic permeability of vacuum I is the electric current dl is an infinitesimal length element of the wire θ is the angle between the element dl and the line connecting the element to the point where the field is calculated r is the distance between the element dl and the point where the field is calculated. 3. Right-Hand Rule
Teach the Right-Hand Rule to determine the direction of the magnetic force. Explain that if the thumb points in the direction of the current and the fingers in the direction of the magnetic field, the palm points in the direction of the magnetic force. Practice with different examples of current and magnetic field orientations to reinforce understanding.
Classroom Questions
1. 1️⃣ A 50 cm long wire carries an electric current of 2 A and is immersed in a uniform magnetic field of 0.3 T. The wire makes an angle of 30° with the direction of the magnetic field. Calculate the magnetic force on the wire. 2. 2️⃣ Using Biot-Savart's Law, calculate the magnetic field at a distance of 10 cm from a long straight wire carrying a current of 5 A. 3. 3️⃣ Determine the direction of the magnetic force acting on a wire carrying a current of 3 A in the +x direction, when the magnetic field is directed towards the +y direction.
Questions Discussion
Duration: 15 - 20 minutes
Purpose
The purpose of this stage is to consolidate the knowledge acquired during the lesson, ensuring that students fully understand the concepts and know how to apply them in different situations. The detailed discussion of the questions and the active engagement of students help reinforce learning and clarify any doubts, promoting a deeper and lasting understanding of the content.
Discussion
- Discussion of Questions
1️⃣ Question 1: A 50 cm long wire carries an electric current of 2 A and is immersed in a uniform magnetic field of 0.3 T. The wire makes an angle of 30° with the direction of the magnetic field. Calculate the magnetic force on the wire.
Explanation: Length of wire (L): 0.50 m Current (I): 2 A Magnetic field (B): 0.3 T Angle (θ): 30°
The formula to calculate the magnetic force is F = I × L × B × sin(θ). Substituting the values: F = 2 A × 0.50 m × 0.3 T × sin(30°) F = 2 A × 0.50 m × 0.3 T × 0.5 F = 0.15 N
The magnetic force on the wire is 0.15 N.
2️⃣ Question 2: Using Biot-Savart's Law, calculate the magnetic field at a distance of 10 cm from a long straight wire carrying a current of 5 A.
Explanation: Distance (r): 0.10 m Current (I): 5 A Magnetic permeability of vacuum (μ₀): 4π × 10⁻⁷ T⋅m/A
The formula for Biot-Savart's Law for a long straight wire is B = (μ₀ / 2π) × (I / r). Substituting the values: B = (4π × 10⁻⁷ T⋅m/A / 2π) × (5 A / 0.10 m) B = (2 × 10⁻⁷ T⋅m/A) × 50 A/m B = 1 × 10⁻⁵ T
The magnetic field 10 cm from the wire is 1 × 10⁻⁵ T.
3️⃣ Question 3: Determine the direction of the magnetic force acting on a wire carrying a current of 3 A in the +x direction, when the magnetic field is directed towards the +y direction.
Explanation: Using the Right-Hand Rule: Thumb points in the direction of the current (+x) Fingers point in the direction of the magnetic field (+y) The palm points in the direction of the magnetic force
Therefore, the magnetic force will be directed in the +z direction.
Student Engagement
1. Student Engagement
- What factors influence the magnitude of the magnetic force in a wire with current?
- How does the orientation of the wire concerning the magnetic field affect the direction and magnitude of the magnetic force?
- Why is it important to understand Biot-Savart's Law when studying magnetism in wires?
- How can the Right-Hand Rule be applied in different practical contexts?
- What other technologies, besides speakers and motors, use the principle of magnetic force in wires with current?
Conclusion
Duration: 10 - 15 minutes
The purpose of this stage is to summarize and consolidate the main points addressed in the lesson, reinforcing students' understanding of the content. Additionally, this stage aims to highlight the connection between theory and practice, as well as the importance of the topic for daily life, ensuring that students recognize the relevance of what they have learned.
Summary
- Concept of magnetism and its relationship with electricity.
- Magnetic force acting on a wire with electric current, using the formula F = I × L × B × sin(θ).
- Biot-Savart Law for calculating the magnetic field around a wire with electric current.
- Right-Hand Rule for determining the direction of the magnetic force.
- Solving practical problems involving the calculation of magnetic forces in wires with electric current.
The lesson connected theory with practice by utilizing everyday examples, such as electric motors and speakers, and by solving practical problems that illustrate the application of the formulas and concepts discussed. In this way, students were able to see how the principles of magnetism and electricity are fundamental to many technologies they use daily.
Understanding the magnetic force in wires with electric current is crucial for comprehending the functioning of various technological devices, such as electric motors, generators, and transformers. Furthermore, knowledge of magnetism is applied in areas such as medicine (magnetic resonance), telecommunications (antennas), and navigation (compasses), demonstrating the broad practical relevance of the topic.
