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Fu-Kwun Hwang
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 « Embed this message on: March 10, 2010, 06:00:27 pm » posted from:Taipei,T'ai-pei,Taiwan

The following applet show interaction force between a circular current loop in magnetic field generated by a magnet.
Red arrow show the direction of the current.
Blue arrow are force $\vec{F}=i d\vec{\ell}\times \vec{B}$ due to current loop in magnetic field generated by a magnet.

You can change the location of magnet with two sliders (move in y/z direction).
The radius R of the current loop can be changed with slider,too.
Click play to trace out the magnetic field lines (produced by magnet).

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lookang
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 « Embed this message Reply #1 on: July 05, 2010, 08:51:18 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

Hi prof, this applet is simply fantastic!

the play button seems to work only for the initial conditions.

i moved the slider and click play, it doesn't seems to show the magnetic field lines from the bar magnet.

chance to check it out and enhance it? thanks!

question:
i would make x slide able all the way inside the metal coil, it is the calculation is different thus u made it to only move on the one side of the coil?
It would be a great tool if they can explore left, centre and right of the coil.
for ur consideration!
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Fu-Kwun Hwang
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 « Embed this message Reply #2 on: July 05, 2010, 11:59:28 am » posted from:Taipei,T\'ai-pei,Taiwan

Thank you for the bug report.
It should be fixed now. Please check it again!
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lookang
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 « Embed this message Reply #3 on: July 05, 2010, 11:37:06 pm » posted from:Singapore,,Singapore

bug when z =! 0.

by the way is it that the codes to draw magnetic field lines is hard that the reason why i haven't seen much magnetic field lines in Ejs applet?
only magnetic field vectors is pretty common now

i being thinking i need to add magnetic field lines one day on all my other applets because the sg syllabus still mention it. or should the syllabus be changed to include field vectors to replace field lines?
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Fu-Kwun Hwang
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 « Embed this message Reply #4 on: July 06, 2010, 11:40:49 am » posted from:Taipei,T\'ai-pei,Taiwan

Bug for z!=0 is fixed!
Thank you!
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lookang
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 « Embed this message Reply #5 on: July 06, 2010, 04:02:39 pm »

should the syllabus be changed to include field vectors to replace field lines concept?

any thoughts on this?
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Fu-Kwun Hwang
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 « Embed this message Reply #6 on: July 06, 2010, 05:34:59 pm » posted from:Taipei,T'ai-pei,Taiwan

It is much easier to calculate the field vector.
However, the simulation need to following the field vector in order to draw the field line.
You might want to check out how the field lines were generated from field vector. (the evolution page)

It might be easier for students to visualize magnetic field line than magnetic field vector.
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ahmedelshfie
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 « Embed this message Reply #7 on: July 06, 2010, 05:58:09 pm » posted from:SAO PAULO,SAO PAULO,BRAZIL

Another ask when i set value R=0.5,y=0.5,z=-0.000
I notice line begin from gray arrows so i ask teacher physic and we test so find that:
Line begin from gray arrow not begin from N i add button step for we test step by step and can watch lines more slowly
So prof my ask when set value that i typing up line begin from gray arrows or must begin from N
I will attach image for applet by value that i set up and how he begin
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lookang
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 « Embed this message Reply #8 on: July 06, 2010, 06:27:06 pm »

to ahmed
I think It does not matter because the field lines is just the line of force if there is a particle that is affected by the field lines.

Starting from the N pole has some advantage when we explain it to students.

To prof Hwang.
Can add the field lines arrows too to make the visualization of field lines consistent with the convention adopted by textbook?
Thanks !
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ahmedelshfie
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 « Embed this message Reply #9 on: July 06, 2010, 06:35:09 pm » posted from:SAO PAULO,SAO PAULO,BRAZIL

Is not a bug but I'm just notice so i perfer ask prof to understand this part
However you think this point no make students mix or someting like it ?
Prof Hwang could you if have time modified applet to when run line begin from N
Thanks
 « Last Edit: July 06, 2010, 08:05:41 pm by ahmedelshfie » Logged
Fu-Kwun Hwang
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 « Embed this message Reply #10 on: July 06, 2010, 10:08:21 pm » posted from:Taipei,T\'ai-pei,Taiwan

The purpose of the above applet is to show the force on a current loop in a magnetic field.
$\vec{F}= I d\vec{\ell}\times \vec{B}$

The magnetic field line is a by product.

So all the magnetic field line pass throught the current (event when magnet is off-axis).
That is the reason , the field line starts from the current loop.

If you just need to show magnetic field lines for a bar magnet, I can modify the code to create another simulation:
1. remove current loop and other.
2. let field line starts from N pole.
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ahmedelshfie
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 « Embed this message Reply #11 on: July 06, 2010, 11:15:41 pm » posted from:SAO PAULO,SAO PAULO,BRAZIL

I'm plane publish this simulation so in books here show line Begin from N
They may no understand java is not easy do the same like education or books however
Applet is wonderful.
If have a way to modified code it will be nice for line start fron N
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lookang
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 « Embed this message Reply #12 on: August 20, 2010, 08:34:02 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

found this

Title: The Falling Coil Applet

An interactive Java 3D applet field shows the field configuration around a non-magnetic ring as it falls under gravity in the field of a fixed magnet. In the initial configuration the coil has no resistance and levitates in the field of the magnet. Hit run and let the ring bounce several times. At the bottom of a bounce hit the "iron filings" box to see a representation of the complete field. Hit run again and increase the resistance to "10" using the slider. Watch the subsequent behavior of the ring.

The Ejs applet above is fantastic! now with field lines too! thanks Prof Hwang. i will download and learn

http://web.mit.edu/8.02t/www/802TEAL3D/teal_tour.htm
this The Falling Coil Applet by MIT has a special button on the middle right, it is called magnetic field lines by iron filing.
i think it is drawn using a techniques called line "Dynamic Line Integral Convolution for Visualizing Streamline Evolution"
The paper is here
http://icampus.mit.edu/projects/Publications/TEAL/DynamicLineIC.pdf

The way they did it was by using a plane, to allow such a visualization . I can't understand the mathematics, maybe you can explore if it can be done on Ejs! Thanks!

Pedagogy wise, it is a good visualization feature to have, because it allow students to relate back to real life "iron filing" representation of magnetic field lines.

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lookang
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 « Embed this message Reply #13 on: September 01, 2010, 01:57:25 pm »

yes, i tried to change the codes to make it possible to change the number of lines, i think it was some np or something, if i start with 2, it draw correctly.

but when i add slider to control it, it was some new errors i have no seen before and it was stuck for a while.

the final goal is i hope to make it like the MIT TEAL applets visualization, which i should be able to do more it i can figure out the codes better, like the vernier caliper model, DC motor etc.

i seem to have misplaced the working file, will attach it when i find it
 « Last Edit: September 01, 2010, 02:06:36 pm by lookang » Logged
Fu-Kwun Hwang
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 « Embed this message Reply #14 on: September 01, 2010, 03:30:30 pm » posted from:Taipei,T\'ai-pei,Taiwan

nc is the number of coils for the calculation.
np is the number of points for each coil for the calculation.

Number of filed lines are defined by nf (default=24). You might be able to change it to smaller value.
However, you can not change it to larger number without redefine all those array for (xf,yf,zf,...).
You need to redefine the default for nf if you need more number of lines and do not forgot to call _initialize().

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dona4997
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 « Embed this message Reply #15 on: June 06, 2015, 10:14:45 am » posted from:,,Satellite Provider

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lookang
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 « Embed this message Reply #16 on: June 06, 2015, 12:56:07 pm » posted from:,,Satellite Provider

Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
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"In theory, theory and practice are the same. In practice, they are not." ..."Albert Einstein (1879~1955, Mathematical physicist, Nobel Prize 1921-Physics)"