Post by: Mitko Gorgiev on 24/02/2020 21:39:04
THIS POST AND OTHERS BY THE SAME POSTER APPEAR TO BE EDUCATIONAL IN NATURE, HOWEVER THEY CONTAIN SERIOUS ERRORS AND SHOULD NOT BE TAKEN AS SCIENTIFIC PRINCIPLES.
The title of this topic is: Is electric current induced in a wire when it is moving perpendicularly to the magnetic lines of force or when it is moving in line with them?, but since the number of characters in the space for the title is limited, I had to shorten it.
I post this topic because I need it for the discussion in the topic "Is Faraday's law of induction true?"
https://www.thenakedscientists.com/forum/index.php?topic=78334.0
One of the consequences derived from the Faraday’s law of induction is the following: when a metal wire is moving in a magnetic field, then the component of the wire’s velocity which is perpendicular to the magnetic lines of force should be the cause for the induced current in it. Since the Faraday’s law of induction is not true (as I assert in the topic mentioned above), this consequence is also untrue. The actual cause for the current in the wire is the component of its velocity which is in line with the magnetic lines of force.
Consider this well-known and most effective experiment: we move a magnet in and out of a solenoid. Instead of moving the magnet, we can do the opposite – move the solenoid, so to say, in and out of the magnet.
In this second case I ask you: Is the wire of the solenoid moving perpendicular to the magnetic lines of force, or is it moving in line with them?
It is obvious that the wire of the solenoid is moving in line with the magnetic lines of force. And, as I said, this is the most effective way of inducing electric current in a wire.
Please watch now this YouTube video, where seemingly it is demonstrated that current is induced in the wire when it is moving perpendicularly to the magnetic field.
The magnet used in the video has approximately the shape as in figure (a) below:
horse shoe magnets1.jpg (19.41 kB . 570x530 - viewed 12479 times)Why is some weak current induced in the moving wire? It is not because of its motion through the magnetic field marked with the four horizontal arrows, but because of the ‘components’ of the magnetic field marked with vertical red and blue arrow.
Please look at the figure (b). Parts of the first magnet are cut off and now the magnetic field has a different form with more upright ‘components’. If the wire is moving through this field with the same velocity as before, then the induced current in it will be greater.
Let’s look now at this drawing:
two separate magnets.png (1.76 kB . 370x126 - viewed 20553 times)In this drawing there are two separate identical magnets, placed so that the magnetic field between them is the same as in the figure(a) above. When the wire is moving down through this magnetic field, then it should happen the same as in the case of figure(a). But no, in this wire no current will be induced because this magnetic field has no vertical ‘component’.
Please read also this: "What type of current is induced in a wire loop which rotates in a magnetic field?"
https://www.thenakedscientists.com/forum/index.php?topic=78515.0
Post by: Origin on 24/02/2020 21:58:48
I post this topic because I need it for the discussion in the topic "Is Faraday's law of induction true?"This was settled almost 200 years ago. You're tilting at windmills.
Post by: Mitko Gorgiev on 24/02/2020 22:09:15
We will see.I post this topic because I need it for the discussion in the topic "Is Faraday's law of induction true?"This was settled almost 200 years ago. You're tilting at windmills.
Post by: hamdani yusuf on 25/02/2020 07:13:30
Let’s look now at this drawing:Have you tried this yourself?
two separate magnets.png (1.76 kB . 370x126 - viewed 1251 times)
In this drawing there are two separate identical magnets, placed so that the magnetic field between them is the same as in the figure(a) above. When the wire is moving down through this magnetic field, then it should happen the same as in the case of figure(a). But no, in this wire no current will be induced because this magnetic field has no vertical ‘component’.
Post by: Mitko Gorgiev on 25/02/2020 09:58:35
No, I haven't.Let’s look now at this drawing:Have you tried this yourself?
two separate magnets.png (1.76 kB . 370x126 - viewed 1251 times)
In this drawing there are two separate identical magnets, placed so that the magnetic field between them is the same as in the figure(a) above. When the wire is moving down through this magnetic field, then it should happen the same as in the case of figure(a). But no, in this wire no current will be induced because this magnetic field has no vertical ‘component’.
Post by: Origin on 25/02/2020 11:27:06
Quote
We will see.We already know. I am afraid you will never know, unless you open your mind to the possibility that your guess is wrong.
Post by: hamdani yusuf on 26/02/2020 03:27:09
Let’s look now at this drawing:What do you think would happen if one of those magnets is removed? Will electric current be induced in the wire?
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30282;image)
two separate magnets.png (1.76 kB . 370x126 - viewed 2629 times)
In this drawing there are two separate identical magnets, placed so that the magnetic field between them is the same as in the figure(a) above. When the wire is moving down through this magnetic field, then it should happen the same as in the case of figure(a). But no, in this wire no current will be induced because this magnetic field has no vertical ‘component’.
Post by: Mitko Gorgiev on 26/02/2020 14:06:17
What do you think would happen if one of those magnets is removed? Will electric current be induced in the wire?I think there would be only a slight difference compared to the case with two magnets.
Please look at figure below:
[ Invalid Attachment ]
The upper and the lower arrow are slightly curved because of the small vertical component at the edges. This component is further smaller if we place two magnets as much as possible close to each other:
[ Invalid Attachment ]
If we let a straight conductor fall down perpendicularly through this field, then on the oscilloscope (the conductor is connected to it) I expect to see two little spikes:
[ Invalid Attachment ]
The first spike should happen in the moment when the conductor is entering the field, the second spike when it is leaving the field. The difference between the two variants of the experiment (that is, with one and with two magnets) should be only in the magnitude of the spikes.
To make this experiment as much as possible ideally, one should take very broad magnets and let the conductor fall from point A to point B, that is, the movement is the whole time inside the field. Then no spikes, no current will be induced at all (figure below).
[ Invalid Attachment ]
Post by: Mitko Gorgiev on 26/02/2020 19:58:10
A conductor is moving uniformly and obliquely through a magnetic field from point A to point C through point B (figure below).
conductor through field.png (2.57 kB . 160x330 - viewed 8301 times)The induced current in the conductor flows away from us along the section AB. In the point B the current drops to zero. Then, in the section BC, begins a current flow in the contrary direction, that is, towards us. The graph will approximately look like this:
graph ABC.png (2.25 kB . 340x260 - viewed 8490 times)I ask you now, how come the current changes its direction at the middle point and also changes its intensity along the way if the perpendicular component of its velocity (in this case it is the horizontal component) is the cause for the current induction?
Post by: hamdani yusuf on 27/02/2020 02:25:30
Let us know if the result agrees with your expectation.
Post by: Mitko Gorgiev on 27/02/2020 07:36:26
Let us know if the result agrees with your expectation.Since you have already linked two videos in the other threads of mine which seemingly contradict my assertions, I assume that this video should also somehow contradict them.
In those videos I have seen what the contradiction is, but in this I cannot. Would you elaborate it, please?
Or maybe you have posted this video only to ask for my opinion, without saying that there is a contradiction to my assertions?
By the way, have you read the last post of mine in this thread? I would love to hear opinions from others - theoretical opinions.
Post by: Bored chemist on 27/02/2020 12:55:11
The induced current in the conductor flows away from us along the section AB. In the point B the current drops to zero. Then, in the section BC, begins a current flow in the contrary direction, that is, towards us. The graph will approximately look like this:
Says who?
That's certainly not what Faraday's law says.
Post by: Mitko Gorgiev on 27/02/2020 19:39:12
I say, Mitko Gorgiev (by the way, it is my real name, I don't hide myself) and everyone can check it easily.The induced current in the conductor flows away from us along the section AB. In the point B the current drops to zero. Then, in the section BC, begins a current flow in the contrary direction, that is, towards us. The graph will approximately look like this:
Says who?
That's certainly not what Faraday's law says.
conductor towards magnet.png (39.6 kB . 460x410 - viewed 6462 times)In the figure (a) a conductor is moving vertically towards the left edge of the magnet. A current is induced in the conductor which flows towards us. In the figure (b) the conductor is moving towards the right edge of the magnet. A current is induced in the conductor which flows away from us. In the figure (c) the conductor is moving exactly towards the middle of the magnet. No current is induced in this conductor.
What will happen if the conductor is moving obliquely from point A to point C?
conductor through field_1.png (2.08 kB . 160x220 - viewed 6446 times)Please, show us now your intellectual abilities and solve this physics task.
Post by: Bored chemist on 27/02/2020 20:05:24
So, a bit like the Earth inductors I asked you about.
Well we have known what happens there for centuries.
Post by: Mitko Gorgiev on 27/02/2020 20:09:14
So, you are moving a wire through (ideally) a uniform field?WOW, what an answer!
So, a bit like the Earth inductors I asked you about.
Well we have known what happens there for centuries.
You have showed your exceptional intellectual abilities once again!
Post by: Bored chemist on 27/02/2020 20:21:49
Post by: Mitko Gorgiev on 27/02/2020 20:31:05
You were so busy calling me an intellectual that you forgot to answer my question.You are so "an extraordinary intellectual", that you always avoid to admit the truth.
I have a word for such people, which I won't say it now.
Post by: Bored chemist on 27/02/2020 21:21:24
Post by: Mitko Gorgiev on 28/02/2020 00:11:28
Let us know your solution, if you are capable of it at all.
Post by: hamdani yusuf on 28/02/2020 10:22:14
I have tried to move a wire in front of a magnet, and I can see some current was generated in the wire by the reading of a milliammeter. The current must form a closed circuit to enable reading. A short conductor falling in a magnetic field may generate eddy current which in turn resist its movement, but it still requires a closed loop.What do you think would happen if one of those magnets is removed? Will electric current be induced in the wire?I think there would be only a slight difference compared to the case with two magnets.
Please look at figure below:
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30300;image)
The upper and the lower arrow are slightly curved because of the small vertical component at the edges. This component is further smaller if we place two magnets as much as possible close to each other:
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30302;image)
If we let a straight conductor fall down perpendicularly through this field, then on the oscilloscope (the conductor is connected to it) I expect to see two little spikes:
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30304;image)
The first spike should happen in the moment when the conductor is entering the field, the second spike when it is leaving the field. The difference between the two variants of the experiment (that is, with one and with two magnets) should be only in the magnitude of the spikes.
To make this experiment as much as possible ideally, one should take very broad magnets and let the conductor fall from point A to point B, that is, the movement is the whole time inside the field. Then no spikes, no current will be induced at all (figure below).
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30306;image)
In my experiment, I can only find one bump of current reading when a neodymium magnet is moved pass the milliampmeter's wire which forms a closed circuit. This agrees with Faraday's law that the current is proportional to dB/dt.
With finite speed, there would be no vertical line on the oscilloscope.
Post by: hamdani yusuf on 28/02/2020 10:25:37
https://en.wikipedia.org/wiki/Faraday%27s_law_of_induction#EMF_for_non-thin-wire_circuits
Quote
EMF for non-thin-wire circuits
It is tempting to generalize Faraday's law to state: If ∂Σ is any arbitrary closed loop in space whatsoever, then the total time derivative of magnetic flux through Σ equals the EMF around ∂Σ. This statement, however, is not always true and the reason is not just from the obvious reason that EMF is undefined in empty space when no conductor is present. As noted in the previous section, Faraday's law is not guaranteed to work unless the velocity of the abstract curve ∂Σ matches the actual velocity of the material conducting the electricity.[28] The two examples illustrated below show that one often obtains incorrect results when the motion of ∂Σ is divorced from the motion of the material.
(https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Faraday%27s_disc.PNG/187px-Faraday%27s_disc.PNG)
Faraday's homopolar generator. The disc rotates with angular rate ω, sweeping the conducting radius circularly in the static magnetic field B (which direction is along the disk surface normal). The magnetic Lorentz force v × B drives a current along the conducting radius to the conducting rim, and from there the circuit completes through the lower brush and the axle supporting the disc. This device generates an EMF and a current, although the shape of the "circuit" is constant and thus the flux through the circuit does not change with time.
(https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/FaradaysLawWithPlates.gif/240px-FaradaysLawWithPlates.gif)
A wire (solid red lines) connects to two touching metal plates (silver) to form a circuit. The whole system sits in a uniform magnetic field, normal to the page. If the abstract path ∂Σ follows the primary path of current flow (marked in red), then the magnetic flux through this path changes dramatically as the plates are rotated, yet the EMF is almost zero. After Feynman Lectures on Physics Vol. II page 17-3
Post by: Mitko Gorgiev on 28/02/2020 11:33:31
I have tried to move a wire in front of a magnet, and I can see some current was generated in the wire by the reading of a milliammeter. The current must form a closed circuit to enable reading. A short conductor falling in a magnetic field may generate eddy current which in turn resist its movement, but it still requires a closed loop.Dear Hamdani,
In my experiment, I can only find one bump of current reading when a neodymium magnet is moved pass the milliampmeter's wire which forms a closed circuit. This agrees with Faraday's law that the current is proportional to dB/dt.
With finite speed, there would be no vertical line on the oscilloscope.
I don't believe in your experimental setups. You have once tried to pervert a very important experiment. Here it is:
https://www.thenakedscientists.com/forum/index.php?topic=78153.msg591478#msg591478
A short conductor falling in a magnetic field may generate eddy current which in turn resist its movement, but it still requires a closed loop.What short conductor? You refer probably to the figure of mine where the conductor is falling inside the magnetic field from point A to point B. But it is not a short conductor. It can be very long and connected to an oscilloscope. The figure shows a cross-section of the conductor. It is viewed sideways. You have completely misunderstood the setup.
* * *
Let me ask you something. Please look at the figure below:
[ Invalid Attachment ]
A conductor is moving from point A to point B with velocity v. This is the first variant.
In the second variant the same conductor is moving from point A1 to point B1 with the same velocity v as in the first variant. In which case the current will be stronger? I claim that in the first case the current will be many, many times stronger. Would you bet with me on this?
* * *
Would you try to answer the question I have asked my opponents above? Let us hear your theoretical opinion.
Post by: Bored chemist on 28/02/2020 18:16:24
The Bored chemist has solved it, but he is ashamed to tell us the solution, because he loses as usual.Until you stop messing about and actually answer the question I asked, I don't know what you are talking about.
Consequently, I can't "solve" it.
I'm obviously not ashamed of your inability to answer a question.
I don't have anything to lose here; I'm still trying to find out what you are talking about.
Post by: Mitko Gorgiev on 28/02/2020 20:40:48
I usually answer your questions, but you never answer my questions. It is true that I am the original poster of this thread, but once you have entered the discussion, then I consider that you have to answer also my questions.The Bored chemist has solved it, but he is ashamed to tell us the solution, because he loses as usual.Until you stop messing about and actually answer the question I asked, I don't know what you are talking about.
Consequently, I can't "solve" it.
I'm obviously not ashamed of your inability to answer a question.
I don't have anything to lose here; I'm still trying to find out what you are talking about.
Hence, answer my question first and then I will answer your question.
hence
Post by: hamdani yusuf on 29/02/2020 11:10:19
What short conductor?See this video. Skip to 2:50
Post by: hamdani yusuf on 29/02/2020 11:12:06
I don't believe in your experimental setupsWhy don't you try it yourself? It's not that difficult.
Post by: Bored chemist on 29/02/2020 11:12:56
So, stop wasting time and explain what you are talking about.
Post by: Mitko Gorgiev on 29/02/2020 15:00:40
You link a video which doesn't have anything to do with the problem we discuss and you avoid to answer my questions.What short conductor?See this video. Skip to 2:50
So, let me remind you:
[ Invalid Attachment ]
Question 1 (figure (a)):
In which case the current will be stronger? When the conductor is moving from A to B or when it is moving from A1 to B1?
Question 2 (figure (b)):
What will happen when the conductor is moving from A to C through B? How will the induced current change?
If you answer my questions, I will answer you why I think that the linked video has nothing to do with the subject here and also other unanswered things, if any.
Post by: Bored chemist on 29/02/2020 15:02:23
You link a video which doesn't have anything to do with the problem we discuss and you avoid to answer my questions.Well, I understood the relevance.
Why don't you?
Post by: Mitko Gorgiev on 29/02/2020 15:05:37
Would you answer the questions for Hamdani?You link a video which doesn't have anything to do with the problem we discuss and you avoid to answer my questions.Well, I understood the relevance.
Why don't you?
Post by: Bored chemist on 29/02/2020 15:08:10
https://www.ebay.co.uk/itm/Fine-Iron-Filings-Fillings-and-Bar-Magnet-Combo-for-magnetism-experiments-200g-/180833657211
which I think we can agree is a "real" picture- not photoshop or whatever.
Here's a clip from it
[ Invalid Attachment ]
And, as you can see the field is not parallel near the end of the magnet.
So, moving a wire in that field will give a rather complicated induced voltage.
That's why I keep asking what sort of field you think you are talking about.
But, because you are not interested in doing science, you don't answer.
Post by: Bored chemist on 29/02/2020 15:10:34
Would you answer the questions for Hamdani?You seem to have forgotten who was asking questions.
What short conductor?
Post by: hamdani yusuf on 02/03/2020 04:02:43
That's exactly why I posted the video of a moving conductor plate around a large magnet.Would you answer the questions for Hamdani?You seem to have forgotten who was asking questions.What short conductor?
Post by: hamdani yusuf on 02/03/2020 04:43:07
So, let me remind you:It depends on the distribution of magnetic flux density in the space cut through by the wire, including the return path to the amperemeter. BC has pointed out that the field is not parallel near the end of the magnet.
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78772.0;attach=30339;image)
Question 1 (figure (a)):
In which case the current will be stronger? When the conductor is moving from A to B or when it is moving from A1 to B1?
Question 2 (figure (b)):
What will happen when the conductor is moving from A to C through B? How will the induced current change?
If you answer my questions, I will answer you why I think that the linked video has nothing to do with the subject here and also other unanswered things, if any.
The video below shows how the magnetic field is distributed around a permanent magnet.
Post by: Mitko Gorgiev on 02/03/2020 20:03:36
It depends on the distribution of magnetic flux density in the space cut through by the wire, including the return path to the amperemeter. BC has pointed out that the field is not parallel near the end of the magnet.This is not an answer. This is only complicating a very simple question, which means avoiding to answer it. I have already answered one of the questions here:.
The video below shows how the magnetic field is distributed around a permanent magnet.
https://www.thenakedscientists.com/forum/index.php?topic=78772.msg594433#msg594433
I think that this is a problem of morality. Some people do not want to admit the truth regardless of how strong are the proofs someone brings forward. And it has to do with the moral.
Post by: Bored chemist on 02/03/2020 20:31:55
Some people do not want to admit the truth regardless of how strong are the proofs someone brings forward.You have not put forward any proofs, so it is not clear what you are talking about.
Post by: hamdani yusuf on 02/03/2020 21:32:21
Unexpected results come from false assumptions. One of yours which I can identify is assuming that magnetic field lines around a magnetic pole are parallel, which is demonstrably false by the experiment.It depends on the distribution of magnetic flux density in the space cut through by the wire, including the return path to the amperemeter. BC has pointed out that the field is not parallel near the end of the magnet.This is not an answer. This is only complicating a very simple question, which means avoiding to answer it. I have already answered one of the questions here:.
The video below shows how the magnetic field is distributed around a permanent magnet.
https://www.thenakedscientists.com/forum/index.php?topic=78772.msg594433#msg594433
I think that this is a problem of morality. Some people do not want to admit the truth regardless of how strong are the proofs someone brings forward. And it has to do with the moral.
When the magnetic field lines are parallel, and we move the magnet relative to conductor along those lines, we got no electric current, as I have shown in my own experiment.
If you have some idea regarding truth and morality, feel free to join my discussion in a thread about universal morality.
Post by: Mitko Gorgiev on 02/03/2020 22:55:27
No, my ideas about morality I will discuss elsewhere, because you are a great disappointment for me.Unexpected results come from false assumptions. One of yours which I can identify is assuming that magnetic field lines around a magnetic pole are parallel, which is demonstrably false by the experiment.It depends on the distribution of magnetic flux density in the space cut through by the wire, including the return path to the amperemeter. BC has pointed out that the field is not parallel near the end of the magnet.This is not an answer. This is only complicating a very simple question, which means avoiding to answer it. I have already answered one of the questions here:.
The video below shows how the magnetic field is distributed around a permanent magnet.
https://www.thenakedscientists.com/forum/index.php?topic=78772.msg594433#msg594433
I think that this is a problem of morality. Some people do not want to admit the truth regardless of how strong are the proofs someone brings forward. And it has to do with the moral.
When the magnetic field lines are parallel, and we move the magnet relative to conductor along those lines, we got no electric current, as I have shown in my own experiment.
If you have some idea regarding truth and morality, feel free to join my discussion in a thread about universal morality.
So, analyze how much you will what is the field around an ORDINARY CYLINDRICAL MAGNET and then answer the questions.
Post by: Bored chemist on 03/03/2020 07:23:44
, analyze how much you will what is the field around an ORDINARY CYLINDRICAL MAGNET and then answer the questions.What you get will be different from what you have drawn
It's easy enough to do the experiment; why not try it?
Post by: Mitko Gorgiev on 04/02/2021 22:00:38
I have uploaded an experiment video on electric generation by moving magnets through a coil.I didn't think about your experiment at that time because I thought it is not very relevant to the discussed issue.
Let us know if the result agrees with your expectation.
I have watched it again today, replicated it and found the explanation.
I am busy now with another thing, but I hope to write it tomorrow.
Have you perhaps found the explanation in the meantime?
Post by: Bored chemist on 04/02/2021 22:19:46
The results are exactly what we would expect.
Post by: Mitko Gorgiev on 05/02/2021 21:33:13
I have uploaded an experiment video on electric generation by moving magnets through a coil.The explanation of Hamdani’s experiment is pretty simple. The magnetic field is strong only at the ends of the magnet, that is, at its poles. Along the length of the magnet the field is very weak. That’s why there is no current induced in the coil when the pretty long magnet is moving inside the coil.
Let us know if the result agrees with your expectation.
When there is a nut between two magnets which are facing each other with the opposite poles, then the situation is not much different compared to the previous case.
Now the third case:
When there is a nut between two magnets which are facing each other with the same poles, then the induced current is considerably greater than the induced current when we are moving the magnet in or out of the coil with one of the poles ahead. Why?
Look please at the drawing below:
[ Invalid Attachment ]
In the figure (a) the magnet is moving with its plus-pole ahead toward a coil. The induced current is flowing toward us, so to say.
In the figure (b) the magnet is moving away from the coil with its minus-pole ahead (the plus-pole is nearer the coil). But this is happening at the other side of the coil. The induced current has the same direction as in the figure (a).
Look now at this drawing:
[ Invalid Attachment ]
Two magnets with a gap between them are moving leftwards as a whole through a coil as shown in the figure. When the coil is exactly in the middle of the gap, then the induced current in it is twice as strong compared to the case when only one of the magnets is moving. It is so because we have here both cases from the figures a) and b) united in one.
The nut in the Hamdani’s experiment makes actually the gap between the magnets and at the same time keeps them together.
P.S. I call Plus the pole of compass which points North. In relation to this, please see:
Is the designation "positive" and "negative" in electricity arbitrary?
https://www.thenakedscientists.com/forum/index.php?topic=78171.0
Post by: hamdani yusuf on 06/02/2021 06:34:43
The explanation of Hamdani’s experiment is pretty simple. The magnetic field is strong only at the ends of the magnet, that is, at its poles. Along the length of the magnet the field is very weak. That’s why there is no current induced in the coil when the pretty long magnet is moving inside the coil.My explanation is that when the coil is around the middle of magnet array, the action of magnets above the coil is canceled by the magnets below it. When the coil is around the end of magnet array, the action by those magnets is not canceled. When there are two magnet arrays in opposite directions, the actions are doubled.
The iron nut is merely meant to make two magnets with same poles stick together, cancelling the repelling magnetic force. It can be replaced by a non-magnetic object glued to both magnets.
Post by: Hayseed on 07/02/2021 04:09:53
Angle. The first relativity. Then came velocity.