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About

Briefing Document: EJS Lorentz Force 3D Java Applet Simulation Model

1. Overview

This document reviews the "EJS Lorentz Force 3D Java Applet Simulation Model," an interactive educational resource hosted by Open Educational Resources / Open Source Physics @ Singapore. The model is designed to help students understand the Lorentz force, which is the force exerted on a charged particle moving in a magnetic field, and how it applies to current-carrying wires in magnetic fields. The applet is built using EasyJavaSimulation (EJS), making it cross-platform compatible with Windows, MacOSX, and Linux.

2. Main Themes

• Lorentz Force: The central theme is the Lorentz force and its application to current-carrying wires in a magnetic field. The simulation allows users to visualize the relationship between current, magnetic field, and the resulting force.
• Interactive Learning: The simulation prioritizes active learning through exploration and experimentation. Users can manipulate various parameters and observe the effects on the motion of a wire within the magnetic field.
• Hands-On Approach: The materials emphasize real-world examples and encourage engagement, for example, "a real live demo is the best."
• Mathematical & Conceptual Understanding: It caters to different levels of understanding, offering both conceptual explanations (like Fleming's Left-Hand Rule) and mathematical formulations (vector cross-product).
• Physics Principles: Concepts like Newton's First Law, drag force, and the magnetic force equation are explored through the simulation.
• Open Educational Resource: The model is provided as an open educational resource for teachers to use to improve conceptual understanding.

3. Key Ideas & Facts

• Lorentz Force Explanation: The document explains that "A current-carrying wire in a magnetic field experiences a force." The magnitude and direction of this force (F) depend on the current (I), the strength and direction of the magnetic field (B), the length of the wire exposed to the field (L), and the angle between the current and field (ϑ).
• Force Calculation: The force can be calculated using two main approaches:
• Advanced: Using vector cross-product: "F = I ^ B. L where ^ is the cross product"
• O Level/A Level: Using a simplified scalar form: "F = I . B. L.sin ϑ"
• Direction of Force: The direction of the force is "perpendicular to both the current I and the magnetic field B".
• Fleming's Left-Hand Rule: A simplified method, "Fleming’s Left Hand Rule predicts the using the left hand, F (thumb) B (index finger) I (middle finger)". This rule is provided as a tool for O-level students.
• Simulation Features: The applet includes adjustable parameters such as:
• Magnetic field strength (By)
• Current (Ix)
• Position (z)
• Velocity (vz)
• Drag coefficient (b)
• Time of simulation (t)
• Checkbox to graph height vs. time
• Exploration Activities: The provided questions guide users to investigate:
• The motion of the wire in the absence of a magnetic field with varying position, velocity and drag.
• The relationship between the force and varying magnetic field and current.
• The effect of the drag force "drag force = b.v".
• The verification of the hypothesis "F = I . B. L. where ϑ =90 deg".
• Gravity is not modeled: The computer model does not include gravity. This choice is presented as an explicit limitation and topic for evaluation. The document suggests that users suggest with reasons why they agree or disagree with this statement.
• Engage: The document promotes engagement by referring to real life demo on "a wire can jump up even though it is not alive" and use of direct current to create rotary motion as in "some simple toys (e.g Tamiya cars)".
• Software Requirement: The simulation requires the use of Java
• Versatile Tool: The resource is designed for Secondary and Junior College levels and can be embedded in web pages using an iframe.

4. Quotes

• "You can use this hand trick F-B-I to predict the magnetic force from magnetic field and current direction."
• "Personally, i prefer F = I^B*L cross product to predict :)"
• "A current-carrying wire in a magnetic field experiences a force."
• "The magnitude and direction of this force F, depend on four variables: the magnitude and direction of the current (I), the strength and direction of the magnetic field (B), the length of the wire expose to magnetic field is (L), the angle between the current I and field B is (ϑ)"
• "F = I ^ B. L where ^ is the cross product"
• "F = I . B. L.sin ϑ where ϑ is the angle between I and B"
• "The direction of the force F is perpendicular to both the current I and the magnetic field B, and is predicted by the Advanced: right-hand cross-product rule."
• "a real live demo is the best.!!"
• "drag force = b.v."
• "O level and A level: F = I . B. L. where ϑ =90 deg"

5. Educational Value

The applet provides an accessible and interactive way for students to learn about the Lorentz force. The combination of conceptual and mathematical explanations, along with hands-on exploration, makes it an effective educational resource. The inclusion of "explore", "mechanics", "elaborate", and "evaluate" promotes active learning and a deeper understanding of the subject.

6. Conclusion

This EJS Lorentz Force 3D Java Applet Simulation Model offers a powerful tool for teaching electromagnetism. Its ability to visualize complex phenomena and facilitate interactive learning makes it a valuable asset for teachers and students. The focus on both conceptual understanding and mathematical rigor ensures that students gain a thorough grasp of the Lorentz force. The questions also encourage scientific investigation into the simulation.

Lorentz Force Study Guide

Quiz

1. What is the Lorentz force?
2. Describe the relationship between the direction of the magnetic force, the current, and the magnetic field.
3. Explain how Fleming's Left Hand Rule can be used to determine the direction of the magnetic force.
4. State the formula that describes the magnitude of the magnetic force on a current-carrying wire, including the angle between the current and magnetic field.
5. In the simulation, what does the slider labeled 'z' control?
6. In the simulation, what does the slider labeled 'vz' control?
7. What does the simulation demonstrate about the motion of the wire when both the current and magnetic field are set to zero?
8. Explain the effect of the drag coefficient 'b' on the motion of the wire in the simulation.
9. What does the simulation show about the relationship between the magnitude of the current and the magnitude of the force on the wire?
10. According to the text, what is an advanced way of describing force mathematically?

Quiz Answer Key

1. The Lorentz force is the force exerted on a charged particle moving through an electromagnetic field. This force is manifested as a force on a current-carrying wire in a magnetic field.
2. The direction of the magnetic force is perpendicular to both the direction of the current and the direction of the magnetic field. This can be visualized using Fleming's Left Hand Rule.
3. Fleming's Left Hand Rule uses the thumb, index finger, and middle finger, positioned at right angles to each other, to represent the directions of the force (thumb), the magnetic field (index finger), and the current (middle finger).
4. The formula is F = I * B * L * sin(ϑ), where F is the force, I is the current, B is the magnetic field strength, L is the length of the wire, and ϑ is the angle between the current and the magnetic field.
5. The slider labeled 'z' controls the initial vertical position of the wire within the simulation.
6. The slider labeled 'vz' controls the initial vertical velocity of the wire within the simulation.
7. The simulation demonstrates that in the absence of magnetic force the wire will remain motionless unless it has a starting velocity, in which case it will move due to its starting velocity and the force of drag.
8. The drag coefficient 'b' represents the resistance to motion due to air or fluid resistance and opposes the wire's motion. It is described as drag force = b.v.
9. The simulation shows that the magnitude of the force on the wire is directly proportional to the magnitude of the current. Increasing the current increases the force.
10. Force can be mathematically represented as a vector cross-product as F= I ^ B * L.

Essay Questions

1. Discuss the practical applications of the Lorentz force, providing real-world examples. How might the simulation be modified to demonstrate another application?
2. Explain the relationship between the various parameters in the Lorentz force equation (F = I * B * L * sin(ϑ)). Use specific examples with the simulation to support your explanation.
3. Compare and contrast the O level Fleming's Left Hand Rule and the advanced right-hand cross-product rule for determining the direction of the Lorentz force. Discuss why two methods of understanding this concept might be necessary for learners.
4. How does the simulation demonstrate Newton's First Law of Motion? Discuss how each of the adjustable variables in the simulation might affect the wire's motion.
5. The simulation does not include gravity. Evaluate the impact of omitting gravity from the simulation, suggesting changes that might make the model more realistic.

Glossary of Key Terms

• Lorentz Force: The force exerted on a charged particle moving through an electromagnetic field. For a current-carrying wire, it's the force exerted by a magnetic field on the moving charges within the wire.
• Magnetic Field (B): A region in space where a magnetic force is exerted. Measured in Teslas (T).
• Current (I): The flow of electric charge, measured in Amperes (A).
• Length (L): The length of the current-carrying wire exposed to a magnetic field, measured in meters (m).
• Angle (ϑ): The angle between the direction of the current and the direction of the magnetic field.
• Fleming's Left-Hand Rule: A mnemonic tool used to determine the direction of the magnetic force on a current-carrying wire. The thumb indicates the direction of force, the index finger the magnetic field, and the middle finger the current.
• Vector Cross-Product: A mathematical operation between two vectors that results in a third vector perpendicular to both. The cross-product is used in physics to describe quantities like torque and the Lorentz Force.
• Drag Coefficient (b): A numerical value that represents the resistance of an object to motion through a fluid or air. A higher drag coefficient indicates more resistance.
• Newton's First Law of Motion: An object in motion remains in motion unless acted upon by an external force, and an object at rest stays at rest unless acted upon by an external force.

You can use this hand trick F-B-I to predict the magnetic force from magnetic field and current direction.
the above beautiful picture is from image from National High Magnetic Field Laboratoryhttp://www.magnet.fsu.edu/education/tutorials/java/handrules/index.html& Rāhulhttp://empiricisms.wordpress.com/2009/10/11/why-the-left-hand-rule/  Creative Commons Rocks! 
Personally, i prefer F = I^B*L cross product to predict :).

for teachers exercise by lookang 

Introductionwww.bk.psu.edu/faculty/gamberg/mag_lab.doc
A current-carrying wire in a magnetic field experiences a force. The magnitude and direction of this force F, depend on four variables: 
the magnitude and direction of the current (I), 
the strength and direction of the magnetic field (B)
the length of the wire expose to magnetic field is (L)
the angle between the current I and field B is (ϑ) 
Advanced: The force can be described mathematically by the vector cross-product:
O level: Fleming’s Left Hand Rule predicts the using the left hand, F (thumb) B (index finger) I (middle finger) 
image from National High Magnetic Field Laboratoryhttp://www.magnet.fsu.edu/education/tutorials/java/handrules/index.html

Advanced: F = I ^ B. L where ^ is the cross product 
O level and A level: F = I . B. L.sin ϑ where ϑ is the angle between I and B 

where
Force F is in newtons N
current I is in amperes A
length L in meters m
magnetic field B in teslas T

The direction of the force F is perpendicular to both the current I and the magnetic field B, and is predicted by the Advanced: right-hand cross-product rule. 
O level and A level: Fleming’s Left Hand Rule

Engage:
a real live demo is the best.!!
a youtube videohttp://www.youtube.com/watch?v=_X8jKqZVwoI&feature=player_embedded



Engage 1: Would you believe that a wire can jump up even though it is not alive?
Engage 2: have you thought about how a direct current can cause a rotating motion which can be used to drive some simple toys (e.g Tamiya cars) ? 
http://www.tamiya.com/english/products/42183trf502x/top.jpg


Explore
1. Explore the simulation, this simulation is designed with a wire supported by a spring in a system of magnetic fields in y direction.
2 The play button runs the simulation, click it again to pause and the reset button brings the simulation back to its original state.
3 by default values B, I, L, play the simulation. Notice that the wire is in its motionless in its previous state of motion. What is the physics principle simulatted here.
hint: newton's 1st law
4 reset the simulation.
5 using the default values(L = 1 m, ϑ = 90 deg), adjust the value of By =1 and Ix =1 play the simulation. what did you observe? explain the motion in terms of the influences of magnetic field (assume gravitational effect can be neglected, in this computer model gravity is not model)
6 explore the slider z. what do this slider control?
7 explore the slider vz. what does this slider control?
8 by leaving the cursor on the slider, tips will appear to give a description of the slider. you can try it the following sliders such as the drag coefficient b.
9 there are some value of time of simulation t and the checkbox graph for height vs time. 
10 vary the simulation and get a sense of what it does.

11 reset the simulation
Mechanics
12 using the default values (By =0, Ix=0) set z = -0.6, vz=0, b=0). Observe the motion of the wire in the absence of magnetic field. Predict what you will see. Describe the motion of the wire. Explain why this it is so?
hint: select the checkbox to view the scientific graph of height vs t.
13 using the default values (By =0, Ix=0) set z = -0.6, vz=0, b=1). Observe the motion of the wire in the absence of magnetic field. Predict what you will see. Describe the motion of the wire. Explain why this it is so?
hint: select the checkbox to view the scientific graph of height vs t.
14 using the default values (By =0, Ix=0) set z = -0.6, vz=1, b=0). Observe the motion of the wire in the absence of magnetic field. Predict what you will see. Describe the motion of the wire. Explain why this it is so?
hint: select the checkbox to view the scientific graph of height vs t.
15 using the default values (By =0, Ix=0) set z = -0.6, vz=1, b=1). Observe the motion of the wire in the absence of magnetic field. Predict what you will see. Describe the motion of the wire. Explain why this it is so?
hint: select the checkbox to view the scientific graph of height vs t.
16 conduct more scientific inquiry into the simulation if need before the next part of the question.
Elaborate 
17 explain the effects of b, the model used is drag force = b.v.

18 reset the simulation
Magnetic Force
Evaluate:
19 A scientist hypothesis "O level and A level: F = I . B. L. where ϑ =90 deg" play the simulation for different initial condition and design an experiment with tables of values to record systematically, determine whether the hypothesis is accurate. 

20 what is the impact of the ϑ != 90 deg ?
21 Suggest a better hypothesis
22 This computer model does not build in gravity, suggest with reason(s) why you agree or disagree with this statement. You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open EJS Model" from the pop-up menu.  You must, of course, have EJS installed on your computer.  Information about EJS is available at: and in the OSP comPADRE collection 


Have Fun!

video

Java

Worksheet 

Version

http://weelookang.blogspot.sg/2010/11/ejs-open-source-lorentz-force-on.html?m=0

Credits

Francisco Esquembre, lookang

Frequently Asked Questions: Lorentz Force Simulation

1. What is the Lorentz force and how does this simulation help me understand it?
2. The Lorentz force is the force exerted on a charged particle moving in a magnetic field. This simulation focuses on the specific case of a current-carrying wire within a magnetic field. The simulation helps visualize the relationship between the current direction (I), magnetic field direction (B), and the resulting force (F) on the wire. By adjusting the parameters such as the magnetic field strength, current, and length of the wire, and initial conditions, users can observe how these factors influence the magnitude and direction of the force, therefore the motion of the wire.
3. How is the direction of the Lorentz force determined in the simulation?
4. The simulation utilizes two methods for determining the direction of the Lorentz force. The primary rule is explained with a "hand trick" commonly known as the Fleming's Left-Hand Rule. This rule states: if the index finger points in the direction of the magnetic field (B), the middle finger points in the direction of conventional current flow (I), then the thumb will indicate the direction of the force (F) on the wire. Another method mentioned is the cross-product rule (F = I^B * L), which is a more advanced method of determining the force. The simulation visually represents the direction of force based on these rules, though it is only shown indirectly by the direction of the wire's motion.
5. What do the sliders labeled "By", "Ix", "z", and "vz" represent in the simulation?

• By: Controls the strength of the magnetic field in the y-direction (vertical).
• Ix: Controls the magnitude of the current in the x-direction (horizontal).
• z: Sets the initial vertical position of the wire.
• vz: Sets the initial velocity of the wire in the z-direction (vertical).

1. By manipulating these sliders, you can explore how changes in these parameters influence the behavior of the wire.
2. What is the meaning of the "drag coefficient b" in the simulation?
3. The "drag coefficient b" represents the effect of the surrounding medium (like air) on the wire's motion. The drag force acts in the opposite direction to the wire's velocity. Mathematically, the drag force is defined by b*v, where v is the velocity of the wire, so a larger b will lead to a stronger resistive force. By adjusting 'b', users can see how resistance affects the wire's motion, slowing it down or eventually bringing it to a stop.
4. Why does the wire move in the simulation, and what does that reveal about the forces involved?
5. The wire moves because the Lorentz force acts on it when a current is present within a magnetic field. When a current (Ix) passes through a wire exposed to a magnetic field (By), it experiences a force that is perpendicular to both. The direction and magnitude of this force influence the motion of the wire. The direction of the force is given by the left hand rule as mentioned in the second question. The initial z-position and z-velocity, along with drag, can add to or subtract from these effects. Observing the wire's motion directly demonstrates the practical application of the Lorentz force.
6. The simulation does not model gravity. Why, and is this a good approach?
7. The simulation simplifies the model by not including gravity. In some experiments, the magnetic force might be much stronger than the gravitational force, which makes the effect of gravity negligible. By ignoring gravity, the simulation focuses solely on the magnetic force and its interplay with current and magnetic field strength, keeping the analysis simpler. This allows users to investigate the Lorentz force effects without the complication of another force involved. However, for some real-world scenarios, gravity would indeed play a significant role, and thus the user is asked to consider the implications of such a limitation.
8. What is the purpose of the 'height vs. time' graph in the simulation?
9. The 'height vs. time' graph is a visual representation of the vertical (z-axis) position of the wire over time. It plots the wire’s height (z-position) against time (t). By observing the changes in the graph as the parameters change users can get a clear picture of the wire’s motion which allows for a more quantitative and detailed analysis of the system's dynamic behavior.
10. How can I use this simulation to conduct a scientific investigation?
11. The simulation encourages experimentation and hypothesis testing. You can systematically adjust the values of B, I, and L (length, although this is a fixed value), while keeping other values constant, record the results, and analyze them to determine how each factor influences the magnitude of the Lorentz force. You can also vary the parameters z, vz and b, which would affect the motion more broadly. By using this approach users can test a hypothesis regarding the mathematical relationship of F= IBLsinθ and also test the effects of the drag force. By taking careful notes of your observations and findings, the simulation becomes a tool for practical scientific inquiry.