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Briefing Document: EJS Falling Magnet Electromagnetism 3D Model

1. Overview

This document summarizes information about an interactive 3D simulation model of a magnet falling through a conductive ring, focusing on the principles of electromagnetic induction and Lenz's Law. The model was created using Easy JavaScript Simulation (EJS) and is hosted by Open Educational Resources / Open Source Physics @ Singapore. This resource is primarily aimed at secondary and junior college levels for physics education and falls under the category of 'Electricity and Magnetism'.

2. Key Concepts and Principles

Electromagnetic Induction: The simulation demonstrates electromagnetic induction, which occurs when a changing magnetic field induces a voltage (electromotive force or emf) in a conductor. In this case, the moving magnet creates a changing magnetic field around the ring, leading to induced current flow.
Faraday's Law: The document states that "the induced emf is proportional to the negative of the rate of change of magnetic flux Φ." This is a fundamental principle governing electromagnetic induction.
Lenz's Law: This law is also explicitly stated: "the induced current produces magnetic field which tends to oppose the change in magnetic flux that induces such currents." This means that the induced current will generate a magnetic field that resists the change in the magnet's field passing through the ring. This can be demonstrated through the direction of the current.
Magnetic Dipoles: The simulation models the magnet as a vertical array of magnetic dipoles instead of a single dipole. This allows for a more realistic representation of a long magnet.

3. Simulation Description

Visualization: The model visualizes the induced current by showing "very big 'electrons' that move according to the strength of the current." This helps students understand the flow of charge in response to the changing magnetic flux.
Interactive Nature: The simulation is interactive, allowing users to observe the relationship between the magnet's motion and the induced current in real time. It is embedded within a webpage.
Minds-On Questions: The resource includes a set of 'Minds-On' questions which suggests an approach to using the simulation as part of an inquiry learning method. These questions probe students’ understanding of the induced emf and current. These questions include:
"Explain the shape (positive and negative peaks) of the recorded signal."
"Why the peaks are not symmetric?"
"At which moment was the magnetic flux changing most quickly?"
"What was the total change of magnetic flux during the first half of the magnet’s fall - while it was moving in to the coil?"
"What was the total change of magnetic flux during the second half of the magnet’s fall - while it was moving out of the coil?"
"How could you change the simulation to increase the magnitude of the sign?"

4. Technical Details and Development

Technology: The simulation is created using Easy Java Simulation (EJS), requiring Java to run.
Accessibility: The model is accessible on Windows, MacOSX, and Linux systems, including laptops and desktops.
Multiple Runs: The simulation can track up to 5 different color-runs.
Authors: The model is a collaborative effort by paco, lookang, and engrg1.
Adaptation: The model was adapted from an original model to accommodate the long magnet design using an array of dipoles.
MOSEM2: The original simulation was part of the MOSEM2 project.
Blogpost: There is reference to "falling magnet through coil simulation. http://weelookang.blogspot.sg/2013/03/falling-magnet-through-coil-simulation.html" suggesting some further explanation or background may be there.

5. Educational Resources

Worksheets: The resource provides a substantial number of associated worksheets (listed by file name) for student use, which seem targeted at different schools and grade levels (e.g. "AJC", "RVHS", "SRJC") demonstrating flexibility in the resource usage. There is also mention of a “Pre-Activity Worksheet” and "Electromagnetic Induction Post Test”.
Version History: The document records several versions of the simulation, indicating that the model has evolved over time.
Video: There are links to videos which may be useful in helping to understand the simulation.
Other Resources: There is a link to another similar interactive resource using GeoGebra, suggesting the model is part of a wider body of similar resources.

6. Credits and Licensing

Credits: The resource acknowledges the contributions of Maria Jose Cano, Ernesto Martin, Francisco Esquembre, lookang, and sze yee, as well as the MOSEM2 project.
Licensing: The educational content is licensed under the Creative Commons Attribution-Share Alike 4.0 Singapore License, while commercial use of the EasyJavaScriptSimulations Library requires separate contact with the This email address is being protected from spambots. You need JavaScript enabled to view it. team.

7. Related Resources

The webpage provides links to a broad variety of additional physics resources, covering topics ranging from mechanics to electromagnetism, suggesting a larger effort to develop open education resources in the field.
A number of 'tracker' based resources are listed. This suggests a use of video analysis to understand and apply physical principles to real world scenarios.
There are multiple references to authors and workshops conducted by Prof Douglas Brown, Wolfgang Christian and Francisco Esquembre, suggesting a broader project to develop physics simulations.

8. Key Takeaways

This EJS simulation is a valuable tool for teaching electromagnetic induction and Lenz's Law.
The model uses a realistic long magnet comprised of magnetic dipoles.
The interactive visualization enhances student learning.
The availability of worksheets suggests that the simulation is intended for structured classroom use, while the set of questions embedded in the text promotes thinking about the underlying physics principles.
The source links to a wider array of educational resources, indicating a comprehensive approach to physics education using interactive simulations and real world scenarios.

Falling Magnet Electromagnetic Induction Study Guide

Quiz

Answer each question in 2-3 sentences.

According to the provided source, what is electromagnetic induction?
What is the relationship between the induced emf and the rate of change of magnetic flux, as described by Faraday's Law?
What is the role of Lenz's Law in this phenomenon?
How is the magnet modeled in the simulation described in the text?
What does the simulation visualize as moving to indicate current?
What is meant by the "positive and negative peaks" of the recorded signal in the experiment?
Why are the positive and negative peaks described in the source as asymmetric?
According to the source, at which point is magnetic flux changing most quickly?
How might one change the simulation to increase the magnitude of the induced voltage signal?
What does the source say was the origin of the original simulation?

Quiz Answer Key

Electromagnetic induction is the phenomenon where a current is induced in a ring when a magnet falls through it. This occurs due to a changing magnetic flux through the ring.
Faraday’s Law states that the induced electromotive force (emf) is proportional to the negative of the rate of change of magnetic flux. This means a faster rate of change results in a greater induced emf.
Lenz's Law states that the induced current creates a magnetic field that opposes the change in magnetic flux that caused it. This means the induced current will resist the motion of the magnet.
The magnet is modeled as a vertical set of magnetic dipoles, rather than a single magnetic dipole as in previous models. This gives a more realistic representation of a long magnet.
The simulation uses large moving “electrons” to visualize the current. The speed and direction of these “electrons” reflect the strength and direction of the current.
The positive and negative peaks of the recorded signal refer to voltage measurements in the coil as the magnet passes through. The polarity of the voltage changes as the magnet enters and then exits the coil.
The peaks are asymmetric because the speed of the magnet increases as it falls through the coil. This means it will spend less time at the second peak.
The magnetic flux is changing most quickly at the times when the magnet's poles are entering and exiting the coil, where the change in the number of magnetic field lines intersecting the coil is largest.
The magnitude of the induced signal can be increased by changing simulation parameters such as the strength of the magnet, the speed of the falling magnet, or the number of coils.
The original simulation was created as part of the MOSEM2 project.

Essay Questions

Discuss the principles of Faraday’s Law and Lenz’s Law and explain how they relate to the observed phenomena in the falling magnet simulation.
Analyze the simulation's use of a vertical array of magnetic dipoles instead of a single magnetic dipole. What difference does this make and how does it improve the simulation?
Explain the relationship between the rate of change of magnetic flux and the induced voltage. Discuss how this is visualized in the simulation and explain the shape of the recorded signal.
Describe how the falling magnet simulation might be adapted for use in a physics class at different educational levels, such as junior college, high school, or introductory college classes.
Using the falling magnet simulation as a starting point, propose an experiment to further investigate the principles of electromagnetic induction. Include suggestions for data collection and analysis.

Glossary

Electromagnetic Induction: The process where a changing magnetic field produces an electromotive force (voltage) in a conductor.
Magnetic Flux (Φ): A measure of the total magnetic field passing through a given area.
Faraday's Law: A law stating that the induced electromotive force (emf) in a closed loop is proportional to the negative rate of change of magnetic flux through the loop.
Lenz's Law: A law stating that the direction of an induced current is always such that it opposes the change in magnetic flux that caused it.
Electromotive Force (emf): The voltage generated by a changing magnetic field.
Magnetic Dipole: A magnetic entity with two poles (north and south), which can be a physical magnet, a current loop, or an atom.
Rate of Change: The measure of how quickly a quantity is changing with respect to time.
Simulation: A model of a real process or system, used to understand its behavior.
MOSEM2 project: The name of the project that created the original version of the simulation.
Magnetic Field: A region around a magnet or electric current in which magnetic force is exerted.

adapted to fit the new model of a long magnet made by an array of magnetic dipoles instead of the original model of a single magnet dipole.

Long Magnet falling through a ring
When a long magnet falls through a ring, current is induced in the ring. This phenomenon is called electromagnetic induction.

According to Faraday’s law, the induced emf is proportional to the negative of the rate of change of magnetic flux Φ. The direction of the induced current is determined by Lenz’s law, the induced current produces magnetic field which tends to oppose the change in magnetic flux that induces such currents.

The voltage induced when a magnet is falling through a ring is simulated in this experiment, where we model the magnet as a vertical set of magnetic 'dipoles'. The current is visualized by very big 'electrons' that move according to the strength of the current.

Please, complete this set of Minds-On questions:
Explain the shape (positive and negative peaks) of the recorded signal.
Why the peaks are not symmetric?
At which moment was the magnetic flux changing most quickly?
What was the total change of magnetic flux during the first half of the magnet’s fall - while it was moving in to the coil?
What was the total change of magnetic flux during the second half of the magnet’s fall - while it was moving out of the coil?
How could you change the simulation to increase the magnitude of the sign?
The original simulation was created as part of the MOSEM2 project.

For Teachers

falling magnet through coil simulation SRJC

falling magnet through coil simulation.

http://weelookang.blogspot.sg/2013/03/falling-magnet-through-coil-simulation.html
falling magnet through coil simulation.https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_FallingMagnet11_4.3.0.jar
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_FallingMagnet11_4.3.0.jar
author: paco, lookang,and engrg1

made changes:
can track up to 5 different color-runs now
right panel 600 width bigger as suggested by zhiye on another collision sim

Posted 27th March 2013 by lookang lawrence wee

Labels: ELECTRICITY AND MAGNETISM

Software Requirements

Java

Worksheet

Credits

Maria Jose Cano, Ernesto Martin & Francisco Esquembre, lookang, sze yee.

MOSEM2 project.

Frequently Asked Questions About the Falling Magnet Through a Ring Simulation

What is the main phenomenon being explored in the "Falling Magnet Through a Ring" simulation?
The simulation explores the phenomenon of electromagnetic induction. This occurs when a magnet falls through a conductive ring (or coil), causing a change in magnetic flux through the ring, which in turn induces an electromotive force (emf) or voltage and subsequently a current in the ring. The magnitude of the induced voltage and current depends on the rate of change of the magnetic flux. This process is described by Faraday’s law and Lenz’s law.
How is the magnet modeled in this simulation, and why is this approach used?
The magnet is modeled as a vertical set of magnetic 'dipoles,' rather than a single magnetic dipole as in some simpler models. This approach allows for a more accurate simulation of a long magnet, taking into account that its magnetic field isn't uniform and changes along the length. This model also more accurately reflects what would happen in a real-world scenario with a long magnet.
What does the induced current in the simulation look like, and how is its strength visualized? The induced current in the ring is visualized using very large “electrons” that move in the ring. The speed and number of these moving “electrons” correspond to the magnitude of the induced current. Thus a larger current is represented by faster moving and potentially more “electrons”.
According to the simulation, why are there both positive and negative peaks in the recorded signal of induced voltage?
The positive and negative peaks in the recorded signal correspond to the direction of the induced current and voltage as the magnet moves through the ring. When the magnet is entering the ring, the magnetic flux is increasing, and the induced current flows in one direction (producing a positive peak in the induced voltage). As the magnet begins to exit the ring, the magnetic flux is now decreasing and so the induced current flows in the opposite direction (producing a negative peak in the induced voltage). This change in the direction of the induced current and voltage is due to Lenz's law.
Why are the positive and negative peaks in the induced voltage not always symmetrical in the simulation?
The lack of symmetry in the peaks indicates that the rate of change of magnetic flux isn't constant as the magnet passes through the ring. The magnet's magnetic field and the rate at which the magnet moves are not uniform at all times of the falling process, meaning that the increasing magnetic flux when the magnet enters the ring is not exactly the same rate of decrease in flux when it exits the ring. This means that the induced voltage in these two phases will not necessarily be equal.
When is the magnetic flux changing most quickly, according to the simulation?

The magnetic flux changes most quickly when the poles of the magnet (the ends) are passing through the ring. At these times the number of field lines from the magnet going through the ring changes at the greatest rate. This also corresponds to when the magnitude of the induced voltage and current will reach its peak.

How can you modify the simulation to increase the magnitude of the induced voltage and current?
To increase the magnitude of the induced voltage and current, you can change the rate at which the magnetic flux is changing. For example, you could make the magnet fall faster, make the magnetic field of the magnet stronger or have a coil with more loops. All of these would lead to a greater rate of change of magnetic flux, therefore a larger induced voltage and current.
What educational resources and materials are associated with this simulation?
The simulation is part of a broader set of open educational resources, including various worksheets and pre/post-tests designed to help students learn about electromagnetic induction. These materials target secondary and junior college levels, allowing students to explore the concepts interactively and through guided exercises. Several video resources are available as well. These resources show the real-world application and phenomenon this simulation seeks to model.

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Details: Written by Loo Kang Wee; Parent Category: 05 Electricity and Magnetism; Category: 09 Electromagnetic Induction; Published: 26 January 2016; Created: 26 January 2016; Last Updated: 04 January 2025; Hits: 8761