icester
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Posts posted by icester
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It does not matter as long as there is relative motion... No absolute motion can exist or can it?
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38 minutes ago, Strange said:
No, Faraday homopolar generator works with brushing, if you read my post carefully you will find a link to brush less homopolar generator patent which does not work... Anyway here is 100 year old example on page 480 claiming that wire moving in constant uniform magnetic field generates EMF:
A College Text-Book of Physics_ 2nd Ed_ Arthur L Kimball_ 1917
The pdf is too big to attach it here but I can email it to you if you want it...
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16 minutes ago, Strange said:
But I don't believe you have a moving magnetic field.
Can you explain how the disk is magnetised (ie in which direction; where the N and S poles are) and why you think it will generate a changing magnetic field?
Calculate the voltage generated in this way and tell me if your measuring instrument is able to measure it.
Uhm. All of Faraday's experiments. Every similar experiment done at school. Every motor or generator....
You are confusing it with induction, there is no induction when conductor moves with constant velocity in uniform magnetic field just like my experiment shows... I can make the magnet wobble slightly and it will generated sinusoidal AC EMF...
7 minutes ago, icester said:You are confusing it with induction, there is no induction when conductor moves with constant velocity in uniform magnetic field just like my experiment shows... I can make the magnet wobble slightly and it will generated sinusoidal AC EMF...
And there is no changing magnetic field in rotating magnet because it rotates around it's axis of symmetry...
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Just now, Strange said:
That says: "Consider a conducting bar of length l moving through a uniform magnetic field..."
So if you move the wire, you will get a voltage. But your spinning disk does not (as far as I can see) generate a changing magnetic field.
Can you explain how it is magnetised and why you think it will generate a changing magnetic field?
It is the same, relative motion between field and wire. I've done the rotating wire in stationary magnetic field and there was no EMF...
One could simply measure the voltage between the ends of a wire moving in Earth magnetic field but it does not work, but classroom physics says it does...
Just now, icester said:It is the same, relative motion between field and wire. I've done the rotating wire in stationary magnetic field and there was no EMF...
One could simply measure the voltage between the ends of a wire moving in Earth magnetic field but it does not work, but classroom physics says it does...
There is no single experiment to confirm what MIT claims...
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Just now, Strange said:
You'll have to be more specific. I skimmed through a few pages of that but couldn't see anything that corresponds to your setup. Can you specify a page or figure number?
Page 10-7
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8 minutes ago, Strange said:
What is the orientation of the magnetisation of that disk? I am assuming that one face of the disk is the North pole and the other face is the South pole. In which case, the rotation will not have any effect on the magnetic field.
Yes, exactly but MIT physics reference (10.2 Motional EMF) claims it generates EMF: http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide10.pdf
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3 minutes ago, Strange said:
I can't see why you would expect any voltage to be generated. As far as I can see, you have a stationary wire in a static magnetic field.
Magnet is rotating at 10000 rpm... Rotating wire in stationary magnet is the same... But Lorentz believed in aether an absolute motion...
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I have publish a video titled: "Orman Force an influence between charged particle and magnetic field"
Here is the YouTube link: https://www.youtube.com/watch?v=gCYqQ0pAs9o&feature=youtu.be
Also the PDF format document:
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I have conducted yet another experiment with rotating magnetic field and stationary water and salt based ionic cell with stainless steel electrodes and again it has failed to produce expected EMF therefor I now conclude that Lorentz force and law must be defective and or false ...
This inconsistency was also found by Tony Rothman and published in his article with a link here: https://scholarship.haverford.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1062&context=astronomy_facpubs
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On 18.09.2018 at 10:18 PM, Enthalpy said:
You can't get a voltage with that setup. But that's tricky, as electromagnetism uses to be.
Essentially, the moving magnet induces zero voltage in your closed loop as is.
The setup nearest to yours is a homopolar generator, see Wiki. It has moving and immobile conductors, plus (uneasy) sliding electric contacts.
More generally, it takes sliding contacts to produce a DC voltage from induction. A collector for instance.
There is no paradox and no induction (induction requires changes in magnetic field direction and or intensity)... Due to magnetic field copper disk experiences radial emf and brushes simply collect charges in both cases.. The emf is dynamic (rotation speed dependent) but based on static charge and radial path of the virtual conductor has very small amount of charge but faster the brush action more charges are collected thus emf potential is proportional to the brush rotation... The rule of Lorentz force defines the direction of EMF of the rotating virtual current path... Finally, Faraday's motor effect creates torque, thus no free energy generator possible...
Induction works on neutral copper and Lorentz fores needs excess charge of one or the other sign... To produce detectable EMF...
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Sorry, I do not understand...
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No, if one asks for help to resolve the issue then it is nothing more than move in progress direction...
Now my knowledge base has new practical experience and I can move on to design useful device with confidence...
Thank you for helping...
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This morning I decided to check the Homopolar DC Brush-less Generator Patent: https://patents.google.com/patent/US5977684
So I've made a toroidal coil with plastic bobbin and at 10000 rpm scope probe of 1Mohm 15pf connected to my HP 54602A scope again delivered 0 DC offset voltage at 50mV/division range... Since no existing brush-less Homopolar Generator physical device exist I conclude that the invention is a non-worker!
Also according to the mathematical model at: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir3.html#c1
There should be around 800v since there is 1000 turns on the toroidal coil...
Next I shell write a letter to MIT since they are teaching student that there is an EMF at the output of wire segment moving in uniform magnetic field...
http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide10.pdf
Just found a video also reporting 0 EMF voltage:
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No, I only just found the related material and the demo is just 3 days old...
Also, after reading about Faraday's Law deficiencies at : https://arxiv.org/pdf/1601.07750.pdf
I noticed that they have jumped the conclusion by assuming that homopolar generator works based on induction so to me it is not a credible volume of research...
So, I am back with Lorentz and why the voltage is not observed as calculated by 100 year old mathematical model of trivial setup which is currently taught at universities around the World...
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Here is the magnet by itself : and from what I understood you claim that constant velocity motion of uniform magnetic field does not allow for induction in stationary conductor.
If so then I agree but then what is going on with Lorentz force based EMF as claimed in mathematical model in : http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir3.html#c1
Also I found this patent that has the same motion arrangement and it claims the same type of EMF: https://patents.google.com/patent/US5977684
Finaly I found this paper which is hard to understand for me but has links to many relevant devices and concepts : https://arxiv.org/pdf/1601.07750.pdf
This study claims that brush less DC homopolar generators are not possible to construct: https://www.research.manchester.ac.uk/portal/files/54538050/FULL_TEXT.PDF
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Yes, magnet is rotating at 10000 rpm... If I make the magnet wobble then scope shows AC voltage but that is due to induction and not the Lorentz force...
Also if such setup would work it would be better than Hall sensor since it does not require bias current...
A College Text-Book of Physics_ 2nd Ed_ Arthur L Kimball_ 1917 also has such theoretical setup where 1m long wire moves at constant velocity cutting magnetic force lines of the Earth, but could not find a single experimental setup that would confirm such EMF voltage...
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Yes, that is neodymium magnet 1 Tesla at the surface and direction of field is parallel to rotation access (visible face is one pole and back face is the other)...
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Yes, tried wires, coils but I have also noticed that it looks like Faraday's Paradox the case: when magnet rotates but disk is stationary...
Maybe it only works with electrostatic voltmeter but at such low voltage (0.8V calculated using the formulae in the link) the only available instrument would be the non contact electrostatic low voltage/field meter which I do not have it yet...
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Here is my setup with rotating magnet a stationary wire connected to 1 mega ohm scope probe at 50 mV per division scale and there is 0 DC offset at maximum rpm of 10000 or less...
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Yes, I have studied all.
I will post a picture of the experiment equipment in few hours. The magnet rotates up to 12000 rpm it is 101 mm diameter and 60 mm inner diameter...
https://magnes.com.pl/duze-powyzej-20-mm/489--mp-101x60x4-1860578191932.html
And the wire is 0.2mm diameter 20 mm long...
I do not see how induction is possible in constant field and constant velocity but it looks consistent with Lorentz force phenomena...
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Hello, I have made an experiment based on mathematical model of EMF generated in segment of wire moving in constant velocity in uniform magnetic field:
Here is the link to the mathematical model: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir3.html#c1
My problem is that I am not getting any voltage out of wire at any speed up to 100 m/s. The field is 0.5 T and the wire length L is 0.02m...
Please advice...
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Motional EMF
in Speculations
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Rotating yes, but it does not necessary means changing... Cutting magnetic filed lines but each line has the same intensity and direction thus comply with definition of uniform magnetic field... So, as you noted, there is no changing magnetic field... In reality there are no flux lines but only a gradient with axial symmetry...