Фізика 9. Розв'язування задач за темою "Магнітне поле струму. Правило свердлика". Презентація 9 клас

Фізика Онлайн

9 Aug 202311:25

Summary

TLDRThis lesson focuses on solving problems related to the magnetic field generated by an electric current. It introduces the right-hand rule for determining the direction of magnetic field lines and discusses how a compass needle or a coil behaves in different current flow scenarios. Through a series of tasks, students are guided to understand magnetic field strength, pole interactions, and the application of various rules such as Ampère's law. The lesson concludes with homework assignments to reinforce the topic covered, ensuring students have a solid grasp before moving forward.

Takeaways

🔍 The lesson focuses on solving problems related to the magnetic field of current and the right-hand rule.
📋 Before starting the lesson, students should self-assess their understanding of the previous topic using a provided link.
🔄 The direction of the magnetic field is determined by the right-hand rule, depending on the direction of the current flow.
🧭 A compass needle will align with the magnetic field lines generated by the current. The needle’s direction will change if the current’s direction is reversed.
🧲 When a magnetic needle is placed on the opposite side of the conductor, the magnetic poles (north and south) will reverse.
💡 The strength of the magnetic field decreases with distance from the conductor. Points equally distant from the conductor have equal magnetic field strengths.
⚡ In a coil, the right-hand rule can help identify the north and south poles based on the current direction. Like poles repel, while opposite poles attract.
📏 The magnetic field is stronger at points closer to the conductor. When comparing multiple points, proximity determines the magnetic field’s strength.
🧮 When analyzing two coils with current, their interaction can be explained by Ampère's force law. Coils with like poles facing each other will repel.
📚 The homework assignment involves studying paragraph 3 and solving exercises that are similar to the problems discussed in the lesson.

Q & A

What is the main topic of the lesson?
-The main topic of the lesson is solving tasks related to the magnetic field of an electric current.
What is the first step recommended before starting the lesson?
-Before starting the lesson, it is recommended to do a self-check to ensure that the previous topic is well remembered.
What is the rule of thumb used to determine the direction of magnetic induction lines around a conductor with current?
-The rule of thumb used is the right-hand rule for a conductor with current, which states that if you point your thumb in the direction of the current, your fingers will curl in the direction of the magnetic induction lines.
How does the direction of the magnetic field change if the direction of the current changes?
-The direction of the magnetic field will be opposite if the direction of the current changes, as the magnetic field lines are determined by the direction of the current.
What happens when the current flows in a different direction in the wire?
-When the current flows in a different direction, the magnetic field lines will also change direction, aligning with the new flow of the current.
What is the relationship between the distance from the conductor and the strength of the magnetic field?
-The magnetic field is weaker the further away from the conductor, as the strength of the magnetic field decreases with distance.
How can you determine the direction of the magnetic field at point A compared to point B?
-You can use the right-hand rule to determine the direction of the magnetic field. If the magnetic induction lines are arranged in a clockwise direction, and you twist a screw in the same direction with your right hand, the direction your thumb points away from the screw indicates the direction the magnetic field lines go into the screen.
What will happen to the compass needle if the current direction changes?
-If the current direction changes, the compass needle will align itself with the new direction of the magnetic field lines, which will be opposite to the original direction.
How does the interaction between two electromagnets with currents depend on their magnetic poles?
-The interaction between two electromagnets depends on their magnetic poles: like poles repel each other, while opposite poles attract each other.
What will be the effect on the dynamometer if a magnet is suspended above an electromagnet and the circuit is closed?
-If a magnet is suspended above an electromagnet and the circuit is closed, the like poles will repel each other, causing the magnet to move upwards. This will result in the dynamometer showing a lower force as the weight of the magnet decreases.
How can you determine the poles of the electromagnet when the direction of the current is known?
-You can determine the poles of the electromagnet by using the right-hand rule. If you grasp the electromagnet with your right hand such that your fingers point in the direction of the current, your thumb will point towards the north pole of the electromagnet.

Outlines

00:00

🧲 Magnetic Field and Current Flow

This paragraph discusses the concept of magnetic fields created by electric current, using the right-hand rule to determine the direction of magnetic field lines around a conductor. It explains how to visualize the magnetic field using a compass, with the magnetic needle aligning itself with the field lines. The direction of the magnetic field depends on the direction of the current flow, which can be determined by the thumb pointing in the direction of the current using the right-hand rule. The paragraph also explores what happens when the current direction changes, resulting in an opposite magnetic field orientation.

05:02

🤔 Solving Magnetic Field Problems

The second paragraph delves into solving problems related to magnetic fields. It uses diagrams to illustrate how to apply Ampere's right-hand rule to determine the direction of magnetic field lines and the behavior of a compass needle. The paragraph also discusses the interaction between a magnet and a current-carrying conductor, explaining how a compass needle will deflect based on the proximity to the conductor and the direction of the current. It further explores the concept of like poles repelling and unlike poles attracting in the context of magnets and compasses.

10:04

📚 Practical Applications and Homework

The final paragraph wraps up the lesson with practical applications of the concepts discussed, such as determining the poles of a current source and the effect of a magnetic field on a compass needle. It also provides guidance on a homework assignment, suggesting that students practice with similar problems to reinforce their understanding. The paragraph concludes with a summary of the key points and a prompt for students to proceed to the next section of the course material.

Mindmap

Keywords

💡Magnetic Field

A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. In the video, the magnetic field is discussed in the context of the magnetic influence around a current-carrying conductor. For example, when a current flows upwards, the magnetic field lines are formed in a circular pattern around the conductor, as explained using the right-hand rule.

💡Magnetic Flux

Magnetic flux is a measure of the total magnetic field that passes through a given surface. It is a scalar quantity and is related to the number of magnetic field lines that pass through the surface. The video mentions that the strength of the magnetic field, and thus the magnetic flux, decreases with distance from the conductor.

💡Right-Hand Rule

The right-hand rule is a mnemonic for understanding the direction of the magnetic field around a current-carrying conductor. By aligning the fingers of the right hand with the direction of the current, the thumb points in the direction of the magnetic field lines. This rule is used throughout the video to determine the orientation of magnetic field lines and the behavior of magnetic materials in response to the field.

💡Magnetic Induction

Magnetic induction refers to the production of an electromotive force (EMF) across a conductor when it is exposed to a changing magnetic field. The video discusses how the direction of magnetic induction lines is related to the direction of the current and the orientation of the conductor.

💡Compass

A compass is a tool used for navigation and orientation that aligns itself with the Earth's magnetic field, with one end pointing towards the magnetic north pole. In the video, the behavior of a compass needle is used to illustrate the direction of the magnetic field lines around a current-carrying wire.

💡Electric Current

Electric current is the flow of electric charge, typically measured in amperes. The video discusses how the direction of the current affects the formation of magnetic field lines around a conductor. For instance, if the current flows upwards, the magnetic field lines form concentric circles around the conductor.

💡Ampere's Law

Ampere's Law is a fundamental law of electromagnetism that relates the integrated magnetic field around a closed loop to the electric current passing through the loop. The video alludes to Ampere's Law when discussing the interaction between magnetic fields and currents, particularly in the context of two current-carrying conductors.

💡Magnet

A magnet is an object that produces a magnetic field. The video discusses the behavior of magnets in the presence of electric currents, such as how a magnet will be attracted or repelled depending on the orientation of the current-carrying conductor.

💡Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The video explains how the interaction between the magnetic field of an electromagnet and a permanent magnet can be understood using the right-hand rule, and how this interaction affects the force measured by a dynamometer.

💡Dynamo

A dynamo is a device that converts mechanical energy into electrical energy using a magnetic field. The video mentions a dynamo in the context of measuring the force exerted by a magnet, indicating that the force (and thus the reading on a dynamometer) will decrease when the magnetic fields of the electromagnet and the permanent magnet are in the same direction.

Highlights

Introduction to solving magnetic field problems related to electric current.

Self-check before starting the lesson to ensure understanding of the previous topic.

Explanation of the right-hand rule for determining the direction of magnetic field lines around a current-carrying conductor.

Demonstration of how to use the right-hand rule with an example where the current flows upwards.

Illustration of magnetic field lines around a conductor with current flowing upwards.

Application of the right-hand rule to determine the direction of a compass needle near a current-carrying wire.

Discussion on the change in magnetic field direction if the current flow direction is reversed.

Use of the right-hand rule to determine the direction of magnetic field lines around a conductor with current flowing towards and away from the observer.

Comparison of magnetic field strength at different points relative to a conductor.

Analysis of the magnetic field at points A and B, equidistant from a conductor, and their field strength.

Explanation of how the magnetic field direction changes when the compass needle is placed on the opposite side of the conductor.

Introduction to the concept of magnetic poles and their interaction with a current-carrying conductor.

Demonstration of how a compass needle reacts when a permanent magnet is brought near it.

Use of the right-hand rule to determine the direction of magnetic field lines around a current-carrying coil.

Discussion on the behavior of a compass needle when the current direction in a coil is reversed.

Explanation of the interaction between two current-carrying coils and their magnetic poles.

Application of Ampere's law to predict the movement of a compass needle in the presence of another current-carrying coil.

Analysis of the effect of a suspended magnet on a current-carrying coil and the resulting change in the dynamometer reading.

Homework assignment to practice the concepts learned in the lesson.

Conclusion and transition to the next paragraph of the study material.