Did you really have the same idea as me recently. Which kind of tells me there is a zeitgeist that is communicating with our subconscious. I think that's why a lot of inventions or discoveries are invented or discovered at the same time.!
I should note that Faraday's disk itself is an exception to Faraday's law. When the disc rotates there is an emf from v×B, but with no change in the linked flux.There are a few others as well, like when two metal plates with slightly curved edges are rocked in a uniform magnetic field, there can be a large change in the flux linkage without the generation of an emf. Also, another interesting point. Notice how when I moved the whole contraption with the multimeter and the red wire on the magnet, there was no induced voltage. That is because everything is moving, even the measurement reference frame. If I only moved the red wire and the magnet together but left the other wires on the table then I would still get a voltage. That means that when I set the magnet on the moving disk, if the measurement device were rotating with the disk then there would be no voltage induced. Here is a great paper that actually tests out spinning the closing circuit. www.nature.com/articles/s41598-022-21155-x. And a lot of people are getting upset about magnetic field lines in the comments. I didn't make up the concept of magnetic field lines, nor Faraday's paradox. This concept and Faraday's paradox have been discussed for over 200 years, lol.
My Problem with this paradox comes with the fact that if you would have a very long, thin but conductive, axis on which to spin the disc&magnet system on and take the measure from the far end of the axis, far away and thus shielded from the rotating magnet, one would still measure the Voltage, wouldn't you?
just do one more experiment for me with this setup. you have your 2 probes, one on the disk, one on its shaft allright ? now, rotate the magnet over the disk, you supposedly do not get any voltage reading. now, rotate the contact probes too. while you rotate the magnet. and you will highly likely see a voltage. disk it self stays stationary.
Spinning the magnet and the disc together still produces a voltage because OTHER parts of the circuit are stationary. There is still relative motion between the magnet and the circuit, just not between the magnet and the disc specifically. If you put the entire apparatus on a turntable, then you will get no voltage, as expected. As for why the spinning magnet doesn't produce a voltage, actually it does -- but it produces the SAME voltage on both sides of the circuit. If you connected two multimeters to the circuit, one on each side, with a ground connection in the middle, you would see identical voltage readouts on both multimeters.
I hadn't figured out the second part yet,.. and it still might take a second for the understanding to soak in,.. but yes the first part is exactly what I was going to say,.. if he can remember when he drew a dotted line explaining that the circuit went up one brush across the radius of the disc contacting the second brush,.. The circuit will stay in that radius between the two brushes regardless of the position of the disc,.. which I do believe was the entire purpose of using a disc,..
I don't get it. Why when magnet and the disc spinning together it's not "it produces the SAME voltage on both sides of the circuit"? As I understand only difference is speed of the disc and circuit is exactly same.
I think the description that magnetic field lines is just a construct make the most sense to me. An electromagnetic field is literally just described with the polarity and strength of a section of the field, and any "lines" just outline areas where the strength is the same, kind of like a pressure or temperature map.
This makes a lot of sense. Do I understand you to mean that it is like thinking that a topographical map indicates actual lines on the earth rather than a continuously changing elevation?
Yup, when you think about what "lines" actually are, usually it's iron filings (which basically become small temporary bar magnets, of course they're going to make lines) or similar small ferrous substance that'll do the same. Sure you might get field lines that are in consistent places but that's likely due to the size of the iron filings. It's the same with electric fields, something moves because the electric field preferentially goes through it, of course similar substances will go to where the field gets concentrated (which is through the substance that's being affected by the electric field, so you get lines). "Field lines" are just a by product of the testing method, which happen to be useful to describe the field. Now gravity though, that doesn't have field lines but it's still a field
I tried this in college with two toroidal magnets out of speakers (same as you had with your drill) but I machined a brass disk mounted to a brass axle such that the two toroidal magnets were placed on either side of the disk and because the disk was only about an eighth of an inch thick, the natural magnetic attraction of the two magnets clamped and rotated with the disk. I then put a multimeter from a brush on the outside edge of the disk and the axle and noted that in either case (whether magnet was held stationary or allowed to spin with the disk) a voltage was developed. I asked my physics professor and we never figured out what was going on. He referenced a very old book where the author claimed that the resolution lie in something to do with relativity (not around during Faraday). But I honestly never understood it sufficiently. I do remember the author claiming that if two equally charged particles a distance x apart were stationary then the force of repulsion was purely electrostatic. But if you as the observer were moving relative to the two particles, then the observed force between them was then a combination of electrostatic and magnetic because the motion gave rise to magnetic field around the charged particles. I found your description excellent. Now subscribed.
It seems to me that what matters is the fluctuations in the magnetic field. A bar magnet's field appears to rotate with the bar but it could simply be the field growing and shrinking in strength as the bar moves.
This is exactly correct. The magnetic field is a non hysteretic vector. The object that creates the magnetic field is irrelevant. What matters is the strength and direction of the field at any/all points in space. Faraday's laws explicitly state that the voltage is proportional to the negatives rate of change of magnetic field integrated over the closed loop area of the wire the voltage is induced upon. This is why stationary motor windings can create a magnetic field that rotates angle at constant amplitude.
..this is probaly going to be comfusing.. but anyway, faraday didnt know what was creating a magnetic field.. but its electrons movin in unison in a specific direction that creates the field strength faraday measured.. (thers sevral videos on this on YT) ..and since the electron will move around the nucleuses about 0.6C (60% of speed of light) when u rotate a magnet ur rotating the path the electrons take, and also the field (the field will rotate with the magnet), in theory u can strech out the field along the path of the magnet, but it req it to move very fast ..a disk magnet 1m wide magnet would need to move close to 0.6C ....as the time for a fieldline to go from one side to the other (assuming its path is 1dm) 1/(0.6c/0.1) 0.0000000005 seconds (5.5... * 10^-10) ..and yes ur absolutely right there are fluctuations in the field as it moves ...it can also be considered as statically moving with the magnet at speeds below a treshold of 0.6C
@@gizmoguyar so rotating the magnet doesnt rotate the field because the strength and orientation of all points in the field do not change then? there is no particle to be moved so what would you say is the cause of any "rotation" of the field.
@anodude6660 the magnet creates the field, and the field is moving if the magnet moves because of the facts described by previous commenter Patrik, in interesting detail.
@@jazzzzzCat the magnetic field isn’t real in the sense that it is a physical object. It is real in the sense that it describes what the motion of a charged particle would be for all locations in 3d space. If the field line points directly towards or away from the ring magnet, that means a charged particle would move directly towards or away from the ring magnet; so, when it is rotating, the field line would still be pointing in exactly the same direction at the same strength, and the particles would move in the exact same way. Look at the graphics in the video. He moved the arrows in a circle, but there is no change in flux because the arrow is just a representation of the direction a charged particle in that location will move; if we could show it, we’d have an infinite number of arrows. Rotating those arrows doesn’t change the direction or speed at which the particles move because the arrows don’t change orientation or size, therefore the field is exactly the same. For the linear motion, there were no arrows, then orthogonal, then parallel, then orthogonal, then no arrow again. The *change* in direction produced the electric current. There is no change in direction of the field in a non rotating magnet. I have no idea what the other guy is talking about. Sounds like he’s talking about an electric field and not a magnetic one.
It's not the motion of magnetic lines that generate voltage, it's the change of magnetic field. Motion just moves areas of a strong magnetic field relative to wire, thus changing it.
The field doesn't change when the disk is spinning under the magnet. So it isn't just a change of magnetic field, but it is when charges move in a uniform magnetic field, they turn at a right angle. Faradays disk is much easier to explain in terms of Lenz's law. But the question about the field spinning or not is still relevant and not resolved.
I think "cutting field lines" is a red herring. What induces a voltage is a change in flux through a closed circuit, whether the magnet producing that flux is rotating or not is irrelevant. Consider a single wire rotating from the axis. As it rotates past the brushes the enclosed area changes, and flux being field * area this results in the induced voltage. But this requires a finite width brush. In the limit of infinite wires and an infinitely thin brush you will still get a voltage but generate no current. To generate current you require a finite width brush.
If that were true, doubling the width of the brushes should give twice the voltage from the rotating disk, because it doubles the change in area. But that's not what happens.
@@gcewingNo it doesn't. The loop is the disk *and* the wires. The induced EMF here is from the Hall effect. Ordinarily, induced EMF is produced by a changing magnetic field producing a nonconservative electric field. When the wire is moved instead, the actual driver is the Lorentz force, not a nonconservative electric field
I wonder if you can recreate this by taking a magnet to the north or south pool to use the earth's magnetic field as part of the circuit. Infinite energy perhaps?
@@fabledarchon176Why would you need to take a magnet to the north or south pole if you’re going to the north or south pole? This should, however, imply that with the correct ways to amplify the signal, we can generate electricity from our own bodies. In fact, even if we didn’t generate usable energy, it’s entirely possible that this principle is the reason any electrical signals can propagate through our or any other organism’s bodies at all.
∇⃗ ⨯ E⃗ = -∂B⃗/∂t thats, whats going on, not the explanation in the video. There ist a magnetic field B⃗ (flux density) in up-down-direction. If the density of this field varies, an electric field is generated clockwise, or counterclockwise rotating. Due to the material Al, this electric field generates a current in the same, rotating direction: j⃗ = σ E⃗ This current generates an magnetic field, that is directed in the opposit direction to the change in B⃗ it results from ∇⃗ ⨯ H⃗ = j⃗ + ∂D⃗/∂t (with D⃗=0) B⃗ = μ H⃗ so as a result, we are not talking about induction, not about faraday's law, but instead about the full set of maxwell equations. Because it's not the magnetic field of the magnet that generates the effect, but a secondary magnetic field, produced by the magnet a first magnetic field. While the first magnetic field ist independent from radius, the second one is not (eddy current). And that's what can be measured.
Here's the next experiment you need to do: The same spinning disk but your closing wires run parallel to the magnetic field (i.e. Straight up and down), so they don't cut through the field lines.
Or instead of a rotating disk, we use a bar. Or. Imagine you have a disk, but it’s slit like a pie in 8 sections, but only have a magnetic slice every other section.
Very cool demonstration of an interesting effect! And as the professor said when the student complained that the result was counterintuitive, "When it comes to rotating invisible fields of force, you have no intuition"
Fermi's Paradox relies on the following, completely unsupported assumptions: Life exists elsewhere in the universe, life always progresses towards complexity, complex life always progresses towards tool use, tool using life always progresses towards civilization, civilization always progresses towards an ever greater energy expenditure. If any one of these assumptions are in fact, not correct, the fundamental assumption of there being anyone to see breaks down. Modern science cannot currently experimentally determine which, if any are correct, so in following with the rhetoric of the scientific method, we should throw out any assertion that 1) relies on existing evidence being wrong, or 2) cannot be reshaped into a testable hypothesis on it's own. Of the assumptions above only the first and last can actually make a prediction that we can test (this is the effort of the Mars missions undertaken every decade or so, and the Kardashev scale) and thus must be discarded. Paradox solved.
It's not a paradox, just a lack of understanding of scales. ie. space is unfathomably huge... you could say astronomical :-), and though the estimated number of other intelligent civilizations seems large to our human minds, they are tiny with respect to the distances involved, and so we never see each other.
my name is Barry McGrath of Graniteville SC. Here is your answer and my suggested "law". Bipolar magnetic feilds, like water seeking its own level, "seek" their own or regulate their own volume according to their own strength. So you see the spin of the outside object has no power of disrupting said volume shape because it is not displacing any aspect of the magnetic feild. When the magnet spins, that feild is being displaced itself through the twisting of the volume and therefore creating voltage. You are welcome. I love your videos, you are awesome.
REALLY Really need more such videos, As a high school student, it's fascinating for me because I Have learnt about these topics in school and now I'm applying these concepts in this paradoxes which is very cool
Thank you for this. I'm a auto mechanic and I now have a better understanding on how hall effect sensors work. Keep up the awesome content I love learning!
Source of magnetic field is not the outer structure of the disc, but the charge particles inside the disc, rotating disc does not rotate magnetic field, it only creates additional field insignificant to the initial field due to low rotation speed, net field is the superposition of the two fields.
The way i think of this is regarding the fact that this specific magnet has a rotating symmetry, if you rotate it, the magnetic field wouldn't change. The voltage is generated by a relative motion between the field and the wire, not the magnet itself and the wire. Its not that the magnetic field is stationary, its that rotating it doesnt change it. To change the magnetic field you need to either translate it relative to the wire disc, or rotate it into a non symetric axis. I think this confusion is made because of how people usualy describe the magnetic field visually, with single lines going from the center around the object, giving the impression that rotating the object also rotate those "lines", but the fact is that the magnetic field is homogenous around an specific radius distance ring, it doesnt have any "lines", nor any phisical phenomena that "rotates" with it, because magnetic field is an interaction force, and not a physical object
It's neat that the part where you move a wire over the magnet to create charge is basically how electric guitar pickups work. Never thought of it at a larger scale for some reason.
And the movement of the wire across the magnet producing a charge is exactly how an electric guitar pickup works. When you pluck a metal string it moves back and forth over a copper-wound magnet which is grounded to the strings. The tiny electric charge is then amplified; the speed of the back and forth motion of the string electrically reproducing the pitch of the vibrating string.
I think you'll find that the mechanism at work is variable reluctance.; the string moving over the polepiece is altering the strength of the magnetic field impinging on the pickup coil. The strings are either steel or have a steel core and are magnetically suceptible. The strings themselves do not form a closed circuit; the tuning peg end of the strings is isolated electrically from all other parts of the guitar but even if they weren't, the magnetic variation near the pickup pole will persist.
From what you're saying, to actually challenge this paradox. The cable touching the center of the metal plate would have to go perpendicular to it. Then the field of the magnet will not cut through it and thus create a current.
When you spin magnet above starionary circuit nothing should happen. Magnet rotates yes but the magnet field doesnt change. So both are basicly stationary then how there should be voltage if both are stationary? ---- this happen also when magnet is attached to disc... the field is stationary but circuit under it rotates thefore there should be voltage --- nothing confusing therd.
I've been watching your videos for over fives years. It's wonderful to see the production value rising recently but the style staying the same: informative and somewhat entertaining.
I have an answer now; the emf/voltage in the wire is generated by the electrons as we know. The electrons need to be moving in a magnetic field to cause them to side-deflect and the final voltage is the sum of all the deflection forces. Because of uniformity, the magnetic field of the disc is the same if it is moving or not.. this is like seeing a row of 11111 moving along and noticing no change. So when the disc magnet is rotated and the conductor(electron-carrying disc) is stationary, there will be no emf- as the electrons are not moving. When both the magnet and disc are rotating there will be emf as the electrons are moving- as they see a uniform magnetic field- whether the magnet is rotating or not. So if we now rotate the emf sensor with the rotating metal disc(as in my last month's comment) there will be an emf according to the above. The wires of the external circuit being stationary or not doesn't make a difference- contrary to what has been suggested by some books.
I have a BSEE with a focus in EM and about to finish my MSEE for EM as reference to my perspective on this paradox. If a charge is stationary due to no source then rotating produces a path for the electrons around the disk, essentially making a loop antenna. This produces a linear polarization with electric fields matching the magenets electric field patterns where efields are asymptotic at the poles and maximum at the edges, where skin depth happens to be for the electric field to receive charge from the magnet which is essentially a magnetostatic infitesimal dipole array. This then offers a singal received by the rotating metal disk at some frequency which exurts rotation relative to the Lorentz force rated from the mass, dimension, unique properties of the ferrous material and charge present. On the other hand, rotating the magnet should not change this spacial field pattern/lines unless the poles are flipped/displaced in the rotation, thus producing elliptical polarization of nearfield radiated fields. Lack of spinning the metal disk but spinning only the magnet causes pure reflection of any signal back due to short circuit conditions for the 0hz disk. When contacted, as mentioned the field pattern is the same for the magnet whether spinning or not unless flipped by the poles, so charge flowing over these lines attempts to be opposed by the magnet producing transduced forces with the same results as just spinning the metal disk (matching maxima at the edges) except current goes to 0A transient to the surface of a pec and infintite transient to the pmc so a significantly larger charge is expected in the contact experement due to the asymptotic (singular) relation for charges close to the edges where radiation occurs. This all falls in line with antenna theory and is a large part of the contribution Maxwell made to Amperes law, making it symmetrical with Faradays to make the Helmholtz wave equation (and this paradox) possible using displacement currents. TLDR: from antenna theory knowing loop antennas act the same as permanant magnets, I would say that the field pattern does not rotate unless the position of the poles changed given a rudimentary understanding of polarization matching requirements for signal integrity.
8:47 Wait, I thought everyone unanimously agreed that magnetic field lines are not real entites, just a way for us humans to visualise and interpret the magnetic field.
I think the modern view is that the electromagnetic stress tensor is real, and it basically just packages up the magnetic and electric fields in a frame-independent manner. There are then three different perspectives that I see. The first is that the field lines are then just the curves tangential to these force fields in a given frame of reference. So on one hand, the lines of force are just directly derived from the field tensor, and we regard the field tensor as “real,” so in some sense, it feels fair to say that the “field lines” are real. At least, they have real meaning, but do they correspond to a physical object that you could touch? That’s hard to say; they correspond to the streamlines of massless particles, so in that sense, the field lines correspond to physical objects (the trajectories of test particles). The second perspective is that physical quantities can only be said to truly “exist” if they look the same in all frames of reference. So then from this standpoint, “electric field lines” and “magnetic field lines” don’t “physically” exist, because these field lines change shape depending on your frame of reference. But that means the force fields don’t exist either. What exists is the tensor. The third perspective is to adopt a more skeptical attitude. Can we really tell if a mathematically entity physically exists or not, or should we just accept that these mathematical entities represent our observations and not the underlying reality? From this standpoint, you just can’t really call anything “real.” All our equations are just representations of what we see happen. As long as their predictions are accurate, questions of “real” or “not real” are irrelevant.
I think this example is where thinking of literal field lines leads you astray. The truth is there's a field everywhere, and to visualize field lines we just choose a starting point and move tangent to the field where we find it. If you move these visualization lines, this has no barring on the complete field.
I don't know if it is intentional or a coincidence, but the VW bus on your shirt is directly related to this video. The speedometer in that bus (van, car) has a cable driven by the left front wheel, coming up to the back of the instrument panel where it turns a simple aluminum (important that it is a non-ferrous metal) circular disk. A thin air gap separates that from a circular magnet attached to a spring. The relative angular velocity between the aluminum disk and magnetic disk through a similar mechanism related to this video's content, induces eddy currents in the aluminum disk and a resulting torque on the magnet (the speedometer side), which acts linearly against the spring which restores the speedometer needle to zero. So there is a linear relationship between the bus velocity (left front wheel, specifically) and the angle of the speedometer needle. No electronics or wires involved. A purely mechanical system that relies on these magnetic effects. Even though I understand some physics, I was a little confused the first time I came across this in my old VW; I could not understand how the speedometer could possibly work.
This blew my mind. I reasoned out that the full circuit mattered just about before you started explaining it. I wonder what sort of fun could one have with spinning semiconductors. A spinning silicon disk that's npn or pnp could act like a transistor that's spinning constantly. So the magnetic field is like a potential voltage when the base of the disk transistor has a voltage applied to it. I could picture a wild rube goldberg type analog/digital computer. Maybe you get to dope the different layers in 2 dimensions now to create interesting oscillations... a NPN transistor could be swapped to a PNP one, or the values changed so that radially the transistor has different values depending on its rotation. Interesting ideas just from your video.. I love it. Thank you for sharing!
Compared to this video, that video would be 30 seconds long. Metal particles suspended in a medium inside a paper thin confinement. Magnet “viewing paper”
Think simpler than this. The Lorentz force acts orthogonally to the v x B product of the motion of a charged particle in a magnetic field. The electrons are present in the aluminum disc, and rotating the aluminum disc gives them a net velocity on the average (tangential to rotation of the disc). When you impose the magnetic field INTO the disc, you're setting up a classic situation that, locally, looks the same as a charged particle moving through a magnetic field. The Lorentz force is then radial, within the plane of the disc. This force "pushes" the electrons radially, creating a charge gradient in the disc, and thus a measurable voltage. Rotating the magnet imparts no kinetic energy to the electrons in the disk. Rotating the disk does. So this is why the paradox evolves. It's not about relative motion between disc and physical magnet. It's about the motion of the disc itself. The individual electron paths get tricky to work out, because there are going to be eddy effects as an actual radial electron current forms. So it's not quite so simple to work out what the output voltage is "under load" as you draw current. But the Lorentz force says this has to happen, and it does.
It wouldnt matter if the field is rotating or not. The Lorentz force is calculated by: F_L = q • (v × B) with q being a scalar and F_L, v and B a vector. Lets use cylinder coordinates for easier calculation, meaning that instead of x, y, z every vector has the variabales r, phi, z with r being the a radial component, phi an angular component, which you can imagine as the angle of a unit circle when looking at the cylinder from above, and z just being a normal axle or in other words the height of the cylinder. Due to the simple nature of the vector product only the orthogonal parts of the two vectors matter for the magnitude of the resulting third vector and its direction, which is orthogonal to both vectors of the vector product. As we spin the metal plate we have to convert our velocity to an angular velocity. It will have the magnitude w = v/r and we describe the direction with the unit vector e_phi: w = v/r • e_phi = v/r • (0, 1, 0) For the magnetic field we assume that its rotating and has a component coming up the zylinder, meaning it has both a phi and z component: B = B_0 • (e_phi + e_z) = B_0 • (0, 1, 1) Lets only focus on the direction of the Lorentz force. It will be the vector product of the two vectors (0, 1, 0) and (0, 1, 1). Just by the earlier mentioned definition, which states that only orthogonal parts matter for both magnitude and direction, we already see that the rotating component of the B-field doesnt have any impact, as its parallel to the phi component of the angular velocity. And if you calculated the vector product you will come to the result that only the phi component of w and the z component of B matter, which result in a radial Lorentz force. This radial Lorentz force moves charges from the middle to the outside of our plate, which creates a potential difference or in other words, it induces a voltage.
This is one of the most genuinely scientific Action Lab videos I've ever seen. Normally they're just magic tricks that are supposed to be analogous to real concepts.
It sounds really suspicious when the youtuber paid to promote a product says “it has been found that the optimal health benefits are found at 3x the government reccomendations”
This is common knowledge. The recommendations given by the government are to prevent the most common disorders associated with each nutrient, not to optimize health or performance. The govt is telling you what you need to get a C-, while scientific research is telling you what you need to do to get an A+.
@@That.Guy. yes, the entire world conspired together, bitter enemies all agreed to fake a pandemic, Russia, Iran, North Korea all stepped up and helped Trump fake everything....sarcasm..
When the magnet is placed on the disc and they both spin together, the Voltage you measure is produced in response to the amount of Resistance offered by the closing circuit (metal brush) that crosses the field and if the brush were a different size the voltage registered would be different accordingly. But most importantly, it's about what location (where) in the circuit is offering the resistance to do so and the fact that the location in question offers an amount of resistance that is different from the resistance offered (at the other metal brush) so on essence you have a conversion from Potential to Kinetic energy at a location that offers Potential Difference. It's the potential difference where in this case the Resistance is the phenomenon that can help to expose the Kinetic energy being registered in Voltage. Change the type and/or size of those metal brushes, surely the resistance that does this will change and so therfore so will the amount of Voltage measured.
I think that the problem might be that magnetism is being viewed as an instantaneous force rather than something that can have or give objects inertia/momentum.
I think that the magnetic field needs to be cut simultaneously to produce voltage, so when only the magnet is spinning the magnetic field is not being cut and when the magnet is placed on the disk it is being cut by the wire brushes under the disk.
There is one other aspect that you can explore. In most motors, when you energize them & they rotate, if you apply load to the motor output, unless the frame of the motor is fastened down, it tries to rotate in the opposite direction. In motors with multiple magnetic poles, this "recoil torque" is against the magnetic pole structure. But for the homopolar ("same pole") motor you demonstrate, this does not happen. The recoil torque occurs against the stationary part of the circuit, not the magnet. So you can do this demo: Motor rotor is on bearings free to rotate, as per convention. But also, the magnet & the "stationary" part of the circuit are mounted on bearings. When you power this up, the magnet remains stationary (held by the unavoidable friction) while the "rotor" & the "stationary" circuit rotate in opposite directions. For the demo, you can avoid another set of sliding contacts by mounting a battery as part of the "stationary" circuit. Manually spinning the magnet has no affect upon the motor's characteristics, not will any torque be borne against it.
I saw on your website that you were working on a book titled "Quantum Faith: A Quantum Theory of God". I would be very interested in reading such a book if/when it gets completed. Your channel rocks.
Surround the magnet with a mumetal shell so the field doesn't go beyond the spinning disk and see what happens. Like others have said, the magnet is inducting voltages in the wire/brushes themselves. Spinning it one top with a drill creates equal, opposing voltages on each side and thus the reading ends up at zero still (-1v + 1v = 0).
4:55 this is because the electricity is moving between the two wires (left to right) in the video irrespective if the disc (bottom) is spinning or not. Right?
What we can deduce from the fact that both voltage events occur when the disc spins, is that the magnetic lines of a circular magnet don't inherently change with its spin as no polarity change occurs. The rectangular magnet would not behave the same if spun as the polarity would move the magnetic lines. The way to check this would be spinning the magnet in a gyroscope and seeing if tilting the magnet along its polarity would cause voltage to occur, I suspect it would.
I did a video on the solution. It is the d orbital that causes the magnetic field. When you spin the magnet it does not change the velocity of the unpaired electron. That is a fixed energy. It's quantized. It can't change no matter how fast you rotate the magnet.
I want to see more experiments. 1) the wire at the bottom: make it perpendicular to the disk itself by extending the disk holder, thus eliminating half of the wire from equation. 2) rotate a magnet above a wire.
It's wild to think about just how many devices/components rely on that principle. Speakers/microphones, motors/generators, transformers, inductors, capacitors, antennas, relays... and I'm sure there are more that I haven't thought of. All of them are based on electromagnetic induction.
You’re getting voltage when you rest the magnet on the disc because the disc itself, due to the direct contact with the magnet, is then part of that magnet and you’re inducing the voltage because the two wires that complete the circuit are stationary. The one with the positive lead is where the flux lines of the spinning magnetic field pass by and induce voltage. Its just not doing it where you expected it to.
Should be mentioned that round magnet is isotropical for rotation: one face N, other face S, centred rotation does not create field change (case 2). Should be specified the material of the disc, iron alloy or non-ferous? Is it perfectly isotropical for rotation? (e.g. a radial bolt beneath, to block it on the electric motor shaft, make it non-isotropical). This could change the field when rotating, IF magnetic field exists (case 1). The magnet left on the disc is eccentric, rotating it the field changes )case 3). If magnetic field changes, induction occur.
Path of least resistance to close the circuit generates a Sudo wire through the disk. The "wire" and flux must have relative motion to generate a voltage.
I think the field rotates and gets projected centripetally outward possibly in accordance to a phi like ratio as the two fields are perpendicular to eachother pertaining to electric and magnetic and vacuum allows for eddy current flow from the centripetal force at hand pulling in surrounding electrons via the magnet and conductive plate in a vortex type manner. Just like wind and running water contain ions and being diamagnetic/ dielectic in their nature. Same aspect I believe... maybe test to see if voltage oscillations on the center and radial edges with oscilloscope/multimeter or thermal imaging... Nice work
I believe the field could have a slight flat planar toroidal resemblance in shape projecting, increasing rotation speed may increase voltage if theory is correct but at centripetal rate, voltage will max out and stabilize due to its available surface capacitance, and heat will increase and result in curie breakdown, thats the thoughts I was just given
the choice of using an aluminum disk is a curious one since passing a field through aluminum creates eddy currents that resist the changing field and trys to stop the field from passing and although aluminum is an electrical conductor it isn't an ferromagnet conductor and would not work as a transformer core.(for example) passing the wire in front of what is surely a magnetic pole does indeed induce a voltage in a wire as long as the field is changing (as in moving) and as soon as you stop it the voltage drops to zero, you will find the same effect if you bring the wire towards the face of the magnet and then away in a straight line. The most effiective way of demonstrating the generative effect of a magnet would be to wrap some copper wire around a bar shaped piece of steel then moving one end of the steel towards on pole of the magnet then quickly moving it to the oposite end thus alterating the polarity of the fields (what happens in an electical generator) thanks for your attempt to educate which is a whole lot better than most of the b.s. that's on the tube
Great video and interesting presentation 5:22 remove the disk, then spin the magnet, that will produce electricity not? The disk is blocking the spin effect of magnetic disk's fields, that's why it only generates electricity when you put it on the disk, because the magnetic fields are then generated by the disk as the magnet, in contact with the disk, transfers it's magnetism to the disk effectively making the disk a magnet When the magnet is just above the disk, the "wire" is the size of the disk (which is bigger than the magnet), so spinning the magnet above it will generate no electricity, because the magnetic fields never cross the wire (so from the wire's point of view the magnet is stationary). So it would be the same as holding the magnet stationary above the wire and spinning it would not make any difference as the generated fields will cancel each other. Just an idea
Almost from the start of the video, I was saying "no". Took me a while to figure out why. Decades ago in physics classes, we had a 3-finger rule: Force, magnetic field, and CURRENT. Think of static electricity, or a battery. You can have a voltage, with no current. That's NOT what happens here. It's the current that causes the voltage. Or has physics changed? As for the setup: get a longer axle. 50cm (18 inch) should be enough. That way, the wire touching the axle should be well away from the magnetic field, and not affected. And to see if flux lines are moving, try a container full of ferrofluid.
I observed a couple things that I have questions about. 1. When the drill was rotating does the direction matter? 2. Would suspending the magnet, from a rope or string make a difference if rotating? In either direction while the metal is also spinning.
When the magnet is rotating the magnetic field is not rotating due to uniform shape and density of the magnet, it still goes from north to south of the ring that could be up to down (or vise versa) in this case. so it only induct current when disk (its atoms) are moving through this field. But if the magnet was not uniform in shape or density or if you rotate the magnet in another axis then it inducts current.
my theory on the both discs moving: it's not the rotating magnetic field that induced the current but the interaction of the disc taking the current path through the disc and moving it to keep the electron interaction high enough to read. basically I'm guessing the magnetic field knocks electrons loose and that creates the voltages, but also knocking into atoms knocks electrons loose and magnets help make more electrons come off while moving the disc causes them to move through the magnetic field in disc through the wires. I'm pretty sure it's something to do with the magnetic fields interactions with the nonferrous metals induced magnetic field being dependent on the connection points and the magnetic field in the rotating disc is only ever there when the disk is spinning. A couple tests might be to spin the disc and the magnet in both the same direction and opposite directions to confirm or deny the hypothesis that the line the electrons take, that line has a counter rotational pull to be in the line of the shortest path. meaning the same direction might not produce less than expected. if that fails then maybe something like the path is wound around as the disc spins like a swirling pattern similar to mixing food coloring into a liquid. it's not about if the field moves or not it's there's a problem that defies what should be so what's the reason is basically all this was for me
I’m really curious about why exactly a current flowing through a straight wire creates a circular magnetic field around it. I understand magnetism as a relativistic effect of the electric field, but not why the magnetic field is circular! Please some experts give some insight here
This does not subject to Faraday's Law, but is Lorentz force law. When the disk rotates, the free e- in the metal disk also gets a net velocity that tangent to the circular orbit of the disk. With a station Mag-field perpendicular to the disk, it create a radial Lorentz force that makes the e-flow from center to boundary or vise versa depending on rotation direction. Thus creates a DC voltage. The voltage only generated depend on the rotation of the disk, not the magnet, assume the magnet have a perfect symmetry.
There should be ionizing efect of ultra high speed very strong magnet on dipole ions. That means, although there is no voltage on entire circuit, there is emf on every segment of the circuit and some secondary effects shall be observable when the field is rotating.
Are we sure the electrons on the disk are still moving in a straight line during disc rotation? Is their movement influenced by the magnetic field and spin?
The Faraday Paradox refers to a curious phenomenon in electromagnetism where Michael Faraday discovered that when a conducting loop is moved in a uniform magnetic field, there is no induced electromotive force (emf) in the loop if it is moving parallel to the magnetic field lines, despite the change in magnetic flux. However, when the loop is moved perpendicular to the magnetic field lines, an emf is induced. This paradox can be understood by considering the forces acting on the charges in the wire. When the loop is moved parallel to the magnetic field lines, the charges experience no force due to their motion, resulting in no induced emf. However, when the loop is moved perpendicular to the magnetic field lines, the charges experience a force due to the magnetic field, resulting in an induced emf. The resolution to the paradox lies in understanding that it's not just the motion of the loop that matters but the relative motion between the loop and the magnetic field. When the loop moves parallel to the field, there's no change in the flux through the loop, hence no induced emf. But when it moves perpendicular to the field, there's a change in flux, leading to an induced emf. Faraday's law of electromagnetic induction explains this phenomenon mathematically, stating that the induced emf in a loop is equal to the rate of change of magnetic flux through the loop. So, there's no paradox, just a misunderstanding of the conditions required for electromagnetic induction to occur.
Isn't the answer much simpler that you only get a current if the charges in the disc that are free to move will experience a force due to the 'stationary' magnetic field. The magnet is rotationally symmetric so there is no change in the B field in time. But the negative electrons in the conduction band of the metal experience a lorenz force when they are made to rotate through a stationary magnetic field so they experience a lateral force creating a potential across the circuit. All that matters is that the disc is rotating because that is where the free charges are that will be moved.
If possible can you try an experiment that I came up with. The things you need are an empty room, a light source and you inside the room. What I have in mind is that , when the light source is turned on you are able to see the walls of the room because they reflect light from the light source. But what if we make the surface of the walls so imperfect that in whatever direction light may hit the wall it does not get reflected to atleast a single point in the room. Which means if you observe the room from that point, even if there is a light source in that room, you would not be able to see anything like the wall and the ceiling in the room.
Hi friends. At the first time, i didn't understand but now, it is clear: When the magnet was rotating on this axe, there is no variation of the magnetic files due to motion of the mouvement of the magnet. While making rotating the magnet plus the métal disc, there is the Lenz force, because of the magnet. No problem, just the reverse induced by the move... Isnt'it?
You speak, and i don't understand. It's so clear, just Lenz force, while same effect if the magnet is turning or not. Look at the pôle of the magnet, it is or north, or south. Just à magnetic field and a metal disc in move> induce à current in the disc. It is called lenz force.
Think path of least resistance. When the magnet is in rotation with the disc there is no circulation of current induced in the disc, instead the magnetic field induces current using the path of least resistance across the disc to complete the rest of the circuit. When the disc is stationary and the magnet is motion, the induced current still follows the path of least resistance, in this case, rotating around in the disc itself, the rest of the circuit is of higher resistance and thus ignored by the current flow.
in the magnet spinning only , there is no virtual wire . the electrons are instead displaced by the magnetic field about the conducting disk as they get from the pos to the neg brush
Thanks! I have a PhD, in physics, but i did not see such a simple explanation of this experiment! Maybe if we used resistor underneath the rotating disk of the centrifuge as part of the circuit and measured the current in it by measuring the voltage drop on this resistor everything could be demonstrated more explicitly.
The field has to be stationary that's why when only the magnet rotates there is no voltage but when the disc rotates with /without the magnet the disc moves through stationary field making voltage.
I wonder if your metal brushes, stationary as they are, when your aluminum disk spins, are the brushes disrupting electrons in some manner so that when you drop your magnet on top the spinning disk so both spin together, the electron situation, if any would be caught in the magnets field and be the cause of the voltage readings.
Perhaps with the magnet stationary it has time to emit its field lines, so with the disc spinning, the wire brushes and the aluminum disc catches the em field (voltage). When the magnet spins, it does not have enough time to emit its field lines (no voltage), so when they spin together they are relaying its field lines in sync (voltage).
Yeah, as an electrician this feels like it'd be pretty easy to work through. If you have a voltage you're cutting field lines with a conductor...I tend to side with physics and would just assume it is not immediately apparent where that is taking place. You have to be aware of whether you are producing a DC or AC current, and make sure your meter is setup appropriately.
The second one is easy to explain. The points at which you're attempting to pick up the current aren't changing. If they were rotating around the metal disc at the same speed as the magnet, you'd get a current. And I agree with deusexaethrea for the last one. There are other areas of the circuit which are electrically conductive so you're introducing a moving magnetic field to them which is producing the current.
"Two circuits one field" The electric circuit can be seen as being made up by two sections of wire. Section A is the stationary circuit being the instrument and the wires to the stationary contact points at the center and the peripheral of the disk. Section B is the circuit on the disk between the contact points. At all times when there is a relative motion between the disk and the magnet a voltage is induced in section B. At all times when there is a relative motion between the magnet and section A a voltage is induced in section A. The trick is to observe that A+B makes up a closed loop but the motion of the conducting parts relative to the magnet differ. When both are moving in the field the voltage cancel out. If they move with different speed there will be a non zero loop voltage. When the magnet rotates and all other parts are stationary the sum of voltages in A and B is zero. They are not of the same amplitude and opposite sign, but they entire loop cuts the field lines twice. The flux in circuit A+B does not alter. All flux that enters the loop A+B, exits at the same rate. When the magnet and the disk rotates in conjunction there is no voltage induced in the disk and no voltage in circuit B. But the magnet field lines still enter and leave stationary circuit A. When A and B was both subject to a rotating magnet field the loop voltage cancelled out. With the disk is moving with the magnet, B is in a stationary magnetic field the, flux encircled by circuit A + B is no longer constant. As B resides in a stationary field and A is in a moving field the loop voltage does not cancel out. As B is not exchanging any flux, but A is, the loop A + B flux is in constant change.
with the spinning aluminium disk you're generating a voltage because it's crossing the part of the circuit on the left side view, the side where the larger brush is, between that brush and the small brush. the closer section to the camera view
it's not a paradox at all. in the "non-functional" example, you're not not breaking field lines. to generate voltage in a wire in a field, u have to break them, that's why the disk itself is the exception.
Isn’t it because the wire is officially connected to the center axis of the disk? Therefore the circular magnet field is not actually passing over the wire to complete the circuit when it rotates around the center axis? While you used a circle magnet does this process change at all with the bar magnet you showed later in the ep knowing the bar magnet field rotates? I’m curious about something what happens if you rotate the magnet the opposite direction of the spinning disc? Does anything change? Something like getting negative voltage?
I think the idea of magnetic feil lines comes from the fact that we use iron shavings and 2D methods of viewing a magnetic field. What you are likely seeing is that the magnetic field is less like a set of lines emanating from the magnet and more like a set of shells. I say this because the second experiment with the magnet on a drill has the magnet barely moving but very quickly rotating but the third experiment has the magnet on a spinning plate not perfectly centered causing the magnet to move back and forth making a small current
Isn't also that not the complete disc is acting as conductor, but the biggest portion of the current is going through the shortest line between the two brushes (this path is acting as a virtual stationary wire), thus there's a relative motion between the wire and the rotating magnet?
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action lab?
what happens when magnet rotates opposite direction, does voltage increase?
Anyone remember when we used to have to pause the cd player to roll the passenger window down cuz we didnt want anyone to miss the lyrics.
It's got electrolytes!
Did you really have the same idea as me recently. Which kind of tells me there is a zeitgeist that is communicating with our subconscious. I think that's why a lot of inventions or discoveries are invented or discovered at the same time.!
I should note that Faraday's disk itself is an exception to Faraday's law. When the disc rotates there is an emf from v×B, but with no change in the linked flux.There are a few others as well, like when two metal plates with slightly curved edges are rocked in a uniform magnetic field, there can be a large change in the flux linkage without the generation of an emf. Also, another interesting point. Notice how when I moved the whole contraption with the multimeter and the red wire on the magnet, there was no induced voltage. That is because everything is moving, even the measurement reference frame. If I only moved the red wire and the magnet together but left the other wires on the table then I would still get a voltage. That means that when I set the magnet on the moving disk, if the measurement device were rotating with the disk then there would be no voltage induced. Here is a great paper that actually tests out spinning the closing circuit. www.nature.com/articles/s41598-022-21155-x. And a lot of people are getting upset about magnetic field lines in the comments. I didn't make up the concept of magnetic field lines, nor Faraday's paradox. This concept and Faraday's paradox have been discussed for over 200 years, lol.
My Problem with this paradox comes with the fact that if you would have a very long, thin but conductive, axis on which to spin the disc&magnet system on and take the measure from the far end of the axis, far away and thus shielded from the rotating magnet, one would still measure the Voltage, wouldn't you?
Change the orientation of the wires to perpendicular to the rotating disk.
maybe it's got something to do with a magnetic field oscillating
just do one more experiment for me with this setup. you have your 2 probes, one on the disk, one on its shaft allright ? now, rotate the magnet over the disk, you supposedly do not get any voltage reading. now, rotate the contact probes too. while you rotate the magnet. and you will highly likely see a voltage. disk it self stays stationary.
Couldn't you use the paper that responds to magnetic fields to show if the field is spinning or not?
Spinning the magnet and the disc together still produces a voltage because OTHER parts of the circuit are stationary. There is still relative motion between the magnet and the circuit, just not between the magnet and the disc specifically. If you put the entire apparatus on a turntable, then you will get no voltage, as expected.
As for why the spinning magnet doesn't produce a voltage, actually it does -- but it produces the SAME voltage on both sides of the circuit. If you connected two multimeters to the circuit, one on each side, with a ground connection in the middle, you would see identical voltage readouts on both multimeters.
I hadn't figured out the second part yet,.. and it still might take a second for the understanding to soak in,.. but yes the first part is exactly what I was going to say,.. if he can remember when he drew a dotted line explaining that the circuit went up one brush across the radius of the disc contacting the second brush,.. The circuit will stay in that radius between the two brushes regardless of the position of the disc,.. which I do believe was the entire purpose of using a disc,..
what if we dont spin anything but merely connect 100 wires around the perimeter and switch them electronically to a single wire one after the other?
exactly
I don't get it. Why when magnet and the disc spinning together it's not "it produces the SAME voltage on both sides of the circuit"? As I understand only difference is speed of the disc and circuit is exactly same.
@@АлександрБыков-м4г the disc works as a moving wire between the contacts, other parts of the disc do nothing.
I think the description that magnetic field lines is just a construct make the most sense to me. An electromagnetic field is literally just described with the polarity and strength of a section of the field, and any "lines" just outline areas where the strength is the same, kind of like a pressure or temperature map.
This makes a lot of sense. Do I understand you to mean that it is like thinking that a topographical map indicates actual lines on the earth rather than a continuously changing elevation?
Not sure if when general relativity is accounted for if the field lines rotate with the dragging of the frame.
i mean yeah, that is literally the definition of "field" (in the physics sense).
Yup, when you think about what "lines" actually are, usually it's iron filings (which basically become small temporary bar magnets, of course they're going to make lines) or similar small ferrous substance that'll do the same. Sure you might get field lines that are in consistent places but that's likely due to the size of the iron filings.
It's the same with electric fields, something moves because the electric field preferentially goes through it, of course similar substances will go to where the field gets concentrated (which is through the substance that's being affected by the electric field, so you get lines).
"Field lines" are just a by product of the testing method, which happen to be useful to describe the field.
Now gravity though, that doesn't have field lines but it's still a field
Look up Slo Mo Guys "SPINNING CAMERA Around Magnetic Fields" where you can see the magnetic field.
The shot you use that shows the scientists talking about something was very helpful to illustrate the concept of scientists discussing science.
I tried this in college with two toroidal magnets out of speakers (same as you had with your drill) but I machined a brass disk mounted to a brass axle such that the two toroidal magnets were placed on either side of the disk and because the disk was only about an eighth of an inch thick, the natural magnetic attraction of the two magnets clamped and rotated with the disk. I then put a multimeter from a brush on the outside edge of the disk and the axle and noted that in either case (whether magnet was held stationary or allowed to spin with the disk) a voltage was developed. I asked my physics professor and we never figured out what was going on. He referenced a very old book where the author claimed that the resolution lie in something to do with relativity (not around during Faraday). But I honestly never understood it sufficiently. I do remember the author claiming that if two equally charged particles a distance x apart were stationary then the force of repulsion was purely electrostatic. But if you as the observer were moving relative to the two particles, then the observed force between them was then a combination of electrostatic and magnetic because the motion gave rise to magnetic field around the charged particles.
I found your description excellent. Now subscribed.
Any possibility that you could repeat this experiment and post a video on it? Would be interesting to observe
It seems to me that what matters is the fluctuations in the magnetic field. A bar magnet's field appears to rotate with the bar but it could simply be the field growing and shrinking in strength as the bar moves.
This is exactly correct. The magnetic field is a non hysteretic vector. The object that creates the magnetic field is irrelevant. What matters is the strength and direction of the field at any/all points in space. Faraday's laws explicitly state that the voltage is proportional to the negatives rate of change of magnetic field integrated over the closed loop area of the wire the voltage is induced upon. This is why stationary motor windings can create a magnetic field that rotates angle at constant amplitude.
..this is probaly going to be comfusing..
but anyway, faraday didnt know what was creating a magnetic field..
but its electrons movin in unison in a specific direction that creates the field strength faraday measured.. (thers sevral videos on this on YT)
..and since the electron will move around the nucleuses about 0.6C (60% of speed of light) when u rotate a magnet ur rotating the path the electrons take, and also the field (the field will rotate with the magnet), in theory u can strech out the field along the path of the magnet, but it req it to move very fast
..a disk magnet 1m wide magnet would need to move close to 0.6C
....as the time for a fieldline to go from one side to the other (assuming its path is 1dm) 1/(0.6c/0.1) 0.0000000005 seconds (5.5... * 10^-10)
..and yes ur absolutely right there are fluctuations in the field as it moves
...it can also be considered as statically moving with the magnet at speeds below a treshold of 0.6C
@@gizmoguyar so rotating the magnet doesnt rotate the field because the strength and orientation of all points in the field do not change then? there is no particle to be moved so what would you say is the cause of any "rotation" of the field.
@anodude6660 the magnet creates the field, and the field is moving if the magnet moves because of the facts described by previous commenter Patrik, in interesting detail.
@@jazzzzzCat the magnetic field isn’t real in the sense that it is a physical object. It is real in the sense that it describes what the motion of a charged particle would be for all locations in 3d space. If the field line points directly towards or away from the ring magnet, that means a charged particle would move directly towards or away from the ring magnet; so, when it is rotating, the field line would still be pointing in exactly the same direction at the same strength, and the particles would move in the exact same way.
Look at the graphics in the video. He moved the arrows in a circle, but there is no change in flux because the arrow is just a representation of the direction a charged particle in that location will move; if we could show it, we’d have an infinite number of arrows. Rotating those arrows doesn’t change the direction or speed at which the particles move because the arrows don’t change orientation or size, therefore the field is exactly the same.
For the linear motion, there were no arrows, then orthogonal, then parallel, then orthogonal, then no arrow again. The *change* in direction produced the electric current. There is no change in direction of the field in a non rotating magnet.
I have no idea what the other guy is talking about. Sounds like he’s talking about an electric field and not a magnetic one.
It's not the motion of magnetic lines that generate voltage, it's the change of magnetic field. Motion just moves areas of a strong magnetic field relative to wire, thus changing it.
There was not a paradox
he created it
He is out of idias to make video 😂
I am unsubscribing he thinks we all are stupid
lol right? i'm like no magnetic field shift no magnetic flux = no electron movement aka no power 😆 😆
so earth (with magnetic field) can generate power in an orbiting object?
The field doesn't change when the disk is spinning under the magnet. So it isn't just a change of magnetic field, but it is when charges move in a uniform magnetic field, they turn at a right angle. Faradays disk is much easier to explain in terms of Lenz's law. But the question about the field spinning or not is still relevant and not resolved.
I think "cutting field lines" is a red herring. What induces a voltage is a change in flux through a closed circuit, whether the magnet producing that flux is rotating or not is irrelevant. Consider a single wire rotating from the axis. As it rotates past the brushes the enclosed area changes, and flux being field * area this results in the induced voltage. But this requires a finite width brush. In the limit of infinite wires and an infinitely thin brush you will still get a voltage but generate no current. To generate current you require a finite width brush.
If that were true, doubling the width of the brushes should give twice the voltage from the rotating disk, because it doubles the change in area. But that's not what happens.
@@gcewingNo it doesn't. The loop is the disk *and* the wires. The induced EMF here is from the Hall effect. Ordinarily, induced EMF is produced by a changing magnetic field producing a nonconservative electric field. When the wire is moved instead, the actual driver is the Lorentz force, not a nonconservative electric field
I wonder if you can recreate this by taking a magnet to the north or south pool to use the earth's magnetic field as part of the circuit. Infinite energy perhaps?
@@fabledarchon176Why would you need to take a magnet to the north or south pole if you’re going to the north or south pole?
This should, however, imply that with the correct ways to amplify the signal, we can generate electricity from our own bodies. In fact, even if we didn’t generate usable energy, it’s entirely possible that this principle is the reason any electrical signals can propagate through our or any other organism’s bodies at all.
∇⃗ ⨯ E⃗ = -∂B⃗/∂t
thats, whats going on, not the explanation in the video. There ist a magnetic field B⃗ (flux density) in up-down-direction. If the density of this field varies, an electric field is generated clockwise, or counterclockwise rotating. Due to the material Al, this electric field generates a current in the same, rotating direction:
j⃗ = σ E⃗
This current generates an magnetic field, that is directed in the opposit direction to the change in B⃗ it results from
∇⃗ ⨯ H⃗ = j⃗ + ∂D⃗/∂t (with D⃗=0)
B⃗ = μ H⃗
so as a result, we are not talking about induction, not about faraday's law, but instead about the full set of maxwell equations. Because it's not the magnetic field of the magnet that generates the effect, but a secondary magnetic field, produced by the magnet a first magnetic field. While the first magnetic field ist independent from radius, the second one is not (eddy current). And that's what can be measured.
One thing I love about this channel is how unceremoniously the videos ends.
he said "see you next time", thats a ceremony
Here's the next experiment you need to do: The same spinning disk but your closing wires run parallel to the magnetic field (i.e. Straight up and down), so they don't cut through the field lines.
At least some part of the closing wire has to be not straight up and down, otherwise the circuit won't close
So perpendicular to the disc.
@@mariopasquato yes, but far enough away from the disk that it has no effect.
Or instead of a rotating disk, we use a bar.
Or. Imagine you have a disk, but it’s slit like a pie in 8 sections, but only have a magnetic slice every other section.
Very cool demonstration of an interesting effect! And as the professor said when the student complained that the result was counterintuitive, "When it comes to rotating invisible fields of force, you have no intuition"
Good one ^^
Reminds me of another one: "All models are wrong, but some are more usefull than others."
Flying saucers are powered by the earth’s magnetic field confirmed 😊
Please solve Fermi's Paradox next :)
Maybe, just maybe...our moms were right. We are VERY special.
My mom always used air quotes.
Fermi's Paradox relies on the following, completely unsupported assumptions: Life exists elsewhere in the universe, life always progresses towards complexity, complex life always progresses towards tool use, tool using life always progresses towards civilization, civilization always progresses towards an ever greater energy expenditure.
If any one of these assumptions are in fact, not correct, the fundamental assumption of there being anyone to see breaks down. Modern science cannot currently experimentally determine which, if any are correct, so in following with the rhetoric of the scientific method, we should throw out any assertion that 1) relies on existing evidence being wrong, or 2) cannot be reshaped into a testable hypothesis on it's own. Of the assumptions above only the first and last can actually make a prediction that we can test (this is the effort of the Mars missions undertaken every decade or so, and the Kardashev scale) and thus must be discarded.
Paradox solved.
@@float32 My mommy called me special. I don't know why she called me Ed though, that's not my name.
It's not a paradox, just a lack of understanding of scales. ie. space is unfathomably huge... you could say astronomical :-), and though the estimated number of other intelligent civilizations seems large to our human minds, they are tiny with respect to the distances involved, and so we never see each other.
my name is Barry McGrath of Graniteville SC. Here is your answer and my suggested "law". Bipolar magnetic feilds, like water seeking its own level, "seek" their own or regulate their own volume according to their own strength. So you see the spin of the outside object has no power of disrupting said volume shape because it is not displacing any aspect of the magnetic feild. When the magnet spins, that feild is being displaced itself through the twisting of the volume and therefore creating voltage. You are welcome. I love your videos, you are awesome.
is this a bit like the difference between rotating a cup filled with water and the water not moving vs putting a spoon in the cup?
Spinning of magnet doesn't rotate magnetic field, it just changes the strength of the magnetic field.
REALLY Really need more such videos, As a high school student, it's fascinating for me because I Have learnt about these topics in school and now I'm applying these concepts in this paradoxes which is very cool
Yes me too I studied while prep for jee
Only 60 seconds in and already understand how generators/motors work. 🎉 Phenomenal
Thank you for this. I'm a auto mechanic and I now have a better understanding on how hall effect sensors work. Keep up the awesome content I love learning!
How exactly did this help you understand how a Hall effect sensor works?
I think you have mixed up hall effect sensor with inductive sensor.
@@nowayjose596😂😂😂
another angle: the electrons try to move in a circle. See: particle beams and magnets
Source of magnetic field is not the outer structure of the disc, but the charge particles inside the disc, rotating disc does not rotate magnetic field, it only creates additional field insignificant to the initial field due to low rotation speed, net field is the superposition of the two fields.
The way i think of this is regarding the fact that this specific magnet has a rotating symmetry, if you rotate it, the magnetic field wouldn't change. The voltage is generated by a relative motion between the field and the wire, not the magnet itself and the wire. Its not that the magnetic field is stationary, its that rotating it doesnt change it. To change the magnetic field you need to either translate it relative to the wire disc, or rotate it into a non symetric axis. I think this confusion is made because of how people usualy describe the magnetic field visually, with single lines going from the center around the object, giving the impression that rotating the object also rotate those "lines", but the fact is that the magnetic field is homogenous around an specific radius distance ring, it doesnt have any "lines", nor any phisical phenomena that "rotates" with it, because magnetic field is an interaction force, and not a physical object
*Dr Stone fans already knowing this information:* 🤓
I remember him building one with two big copper discs
Yep 👍
It's amazing how much the anime got right and wrong at the same time but it made it extremely entertaining the way they played out the story
Yeah, schoolers also familiar with this phenomenon
If that magnet was perfectly centered around 5:00 would you get a voltage?
It's neat that the part where you move a wire over the magnet to create charge is basically how electric guitar pickups work. Never thought of it at a larger scale for some reason.
Its how car alternators work also. Just stronger magnets, and a lot more wire
@@dedu458 Yeah i guess thats correct ha. Pretty much all power is generated that way ha
And the movement of the wire across the magnet producing a charge is exactly how an electric guitar pickup works. When you pluck a metal string it moves back and forth over a copper-wound magnet which is grounded to the strings. The tiny electric charge is then amplified; the speed of the back and forth motion of the string electrically reproducing the pitch of the vibrating string.
I think you'll find that the mechanism at work is variable reluctance.; the string moving over the polepiece is altering the strength of the magnetic field impinging on the pickup coil. The strings are either steel or have a steel core and are magnetically suceptible. The strings themselves do not form a closed circuit; the tuning peg end of the strings is isolated electrically from all other parts of the guitar but even if they weren't, the magnetic variation near the pickup pole will persist.
From what you're saying, to actually challenge this paradox. The cable touching the center of the metal plate would have to go perpendicular to it. Then the field of the magnet will not cut through it and thus create a current.
When you spin magnet above starionary circuit nothing should happen. Magnet rotates yes but the magnet field doesnt change. So both are basicly stationary then how there should be voltage if both are stationary? ---- this happen also when magnet is attached to disc... the field is stationary but circuit under it rotates thefore there should be voltage --- nothing confusing therd.
I've been watching your videos for over fives years. It's wonderful to see the production value rising recently but the style staying the same: informative and somewhat entertaining.
nice, I just got here
I have an answer now; the emf/voltage in the wire is generated by the electrons as we know. The electrons need to be moving in a magnetic field to cause them to side-deflect and the final voltage is the sum of all the deflection forces. Because of uniformity, the magnetic field of the disc is the same if it is moving or not.. this is like seeing a row of 11111 moving along and noticing no change. So when the disc magnet is rotated and the conductor(electron-carrying disc) is stationary, there will be no emf- as the electrons are not moving.
When both the magnet and disc are rotating there will be emf as the electrons are moving- as they see a uniform magnetic field- whether the magnet is rotating or not.
So if we now rotate the emf sensor with the rotating metal disc(as in my last month's comment) there will be an emf according to the above. The wires of the external circuit being stationary or not doesn't make a difference- contrary to what has been suggested by some books.
Thank you very much.
I have a BSEE with a focus in EM and about to finish my MSEE for EM as reference to my perspective on this paradox. If a charge is stationary due to no source then rotating produces a path for the electrons around the disk, essentially making a loop antenna. This produces a linear polarization with electric fields matching the magenets electric field patterns where efields are asymptotic at the poles and maximum at the edges, where skin depth happens to be for the electric field to receive charge from the magnet which is essentially a magnetostatic infitesimal dipole array. This then offers a singal received by the rotating metal disk at some frequency which exurts rotation relative to the Lorentz force rated from the mass, dimension, unique properties of the ferrous material and charge present. On the other hand, rotating the magnet should not change this spacial field pattern/lines unless the poles are flipped/displaced in the rotation, thus producing elliptical polarization of nearfield radiated fields. Lack of spinning the metal disk but spinning only the magnet causes pure reflection of any signal back due to short circuit conditions for the 0hz disk. When contacted, as mentioned the field pattern is the same for the magnet whether spinning or not unless flipped by the poles, so charge flowing over these lines attempts to be opposed by the magnet producing transduced forces with the same results as just spinning the metal disk (matching maxima at the edges) except current goes to 0A transient to the surface of a pec and infintite transient to the pmc so a significantly larger charge is expected in the contact experement due to the asymptotic (singular) relation for charges close to the edges where radiation occurs. This all falls in line with antenna theory and is a large part of the contribution Maxwell made to Amperes law, making it symmetrical with Faradays to make the Helmholtz wave equation (and this paradox) possible using displacement currents. TLDR: from antenna theory knowing loop antennas act the same as permanant magnets, I would say that the field pattern does not rotate unless the position of the poles changed given a rudimentary understanding of polarization matching requirements for signal integrity.
8:47 Wait, I thought everyone unanimously agreed that magnetic field lines are not real entites, just a way for us humans to visualise and interpret the magnetic field.
I think the modern view is that the electromagnetic stress tensor is real, and it basically just packages up the magnetic and electric fields in a frame-independent manner.
There are then three different perspectives that I see. The first is that the field lines are then just the curves tangential to these force fields in a given frame of reference. So on one hand, the lines of force are just directly derived from the field tensor, and we regard the field tensor as “real,” so in some sense, it feels fair to say that the “field lines” are real. At least, they have real meaning, but do they correspond to a physical object that you could touch? That’s hard to say; they correspond to the streamlines of massless particles, so in that sense, the field lines correspond to physical objects (the trajectories of test particles).
The second perspective is that physical quantities can only be said to truly “exist” if they look the same in all frames of reference. So then from this standpoint, “electric field lines” and “magnetic field lines” don’t “physically” exist, because these field lines change shape depending on your frame of reference. But that means the force fields don’t exist either. What exists is the tensor.
The third perspective is to adopt a more skeptical attitude. Can we really tell if a mathematically entity physically exists or not, or should we just accept that these mathematical entities represent our observations and not the underlying reality? From this standpoint, you just can’t really call anything “real.” All our equations are just representations of what we see happen. As long as their predictions are accurate, questions of “real” or “not real” are irrelevant.
They're certainly real. You can visualize magnetic lines using iron filings or ferromagnectic fluid.
I think this example is where thinking of literal field lines leads you astray.
The truth is there's a field everywhere, and to visualize field lines we just choose a starting point and move tangent to the field where we find it.
If you move these visualization lines, this has no barring on the complete field.
Wow. A paradox that is resolved yet unresolved!
😂
But it ceases to be a paradox if it's resolved. The fact it's still called a paradox says it all.
@@Biggles732I guess it would be a falsidical paradox in that case. The Monty Hall paradox is an example of a falsidical one.
like the paradox of how this narrator sounds like the honey badger guy in 2024
I don't know if it is intentional or a coincidence, but the VW bus on your shirt is directly related to this video.
The speedometer in that bus (van, car) has a cable driven by the left front wheel, coming up to the back of the instrument panel where it turns a simple aluminum (important that it is a non-ferrous metal) circular disk. A thin air gap separates that from a circular magnet attached to a spring.
The relative angular velocity between the aluminum disk and magnetic disk through a similar mechanism related to this video's content, induces eddy currents in the aluminum disk and a resulting torque on the magnet (the speedometer side), which acts linearly against the spring which restores the speedometer needle to zero.
So there is a linear relationship between the bus velocity (left front wheel, specifically) and the angle of the speedometer needle. No electronics or wires involved. A purely mechanical system that relies on these magnetic effects. Even though I understand some physics, I was a little confused the first time I came across this in my old VW; I could not understand how the speedometer could possibly work.
This blew my mind. I reasoned out that the full circuit mattered just about before you started explaining it. I wonder what sort of fun could one have with spinning semiconductors. A spinning silicon disk that's npn or pnp could act like a transistor that's spinning constantly. So the magnetic field is like a potential voltage when the base of the disk transistor has a voltage applied to it. I could picture a wild rube goldberg type analog/digital computer.
Maybe you get to dope the different layers in 2 dimensions now to create interesting oscillations... a NPN transistor could be swapped to a PNP one, or the values changed so that radially the transistor has different values depending on its rotation.
Interesting ideas just from your video.. I love it. Thank you for sharing!
@electroboom where you at? 👀
The hospital...
@@punknoodles0 🤣
WTF is magnetic viewing paper? Do a video on that!!
Compared to this video, that video would be 30 seconds long. Metal particles suspended in a medium inside a paper thin confinement. Magnet “viewing paper”
You missed an entire dimension to your case trials. Do all the experiments again with the contact brushes spinning.
Think simpler than this. The Lorentz force acts orthogonally to the v x B product of the motion of a charged particle in a magnetic field. The electrons are present in the aluminum disc, and rotating the aluminum disc gives them a net velocity on the average (tangential to rotation of the disc). When you impose the magnetic field INTO the disc, you're setting up a classic situation that, locally, looks the same as a charged particle moving through a magnetic field. The Lorentz force is then radial, within the plane of the disc. This force "pushes" the electrons radially, creating a charge gradient in the disc, and thus a measurable voltage.
Rotating the magnet imparts no kinetic energy to the electrons in the disk. Rotating the disk does. So this is why the paradox evolves. It's not about relative motion between disc and physical magnet. It's about the motion of the disc itself.
The individual electron paths get tricky to work out, because there are going to be eddy effects as an actual radial electron current forms. So it's not quite so simple to work out what the output voltage is "under load" as you draw current. But the Lorentz force says this has to happen, and it does.
It wouldnt matter if the field is rotating or not. The Lorentz force is calculated by:
F_L = q • (v × B) with q being a scalar and F_L, v and B a vector. Lets use cylinder coordinates for easier calculation, meaning that instead of x, y, z every vector has the variabales r, phi, z with r being the a radial component, phi an angular component, which you can imagine as the angle of a unit circle when looking at the cylinder from above, and z just being a normal axle or in other words the height of the cylinder.
Due to the simple nature of the vector product only the orthogonal parts of the two vectors matter for the magnitude of the resulting third vector and its direction, which is orthogonal to both vectors of the vector product.
As we spin the metal plate we have to convert our velocity to an angular velocity. It will have the magnitude w = v/r and we describe the direction with the unit vector e_phi:
w = v/r • e_phi = v/r • (0, 1, 0)
For the magnetic field we assume that its rotating and has a component coming up the zylinder, meaning it has both a phi and z component:
B = B_0 • (e_phi + e_z) = B_0 • (0, 1, 1)
Lets only focus on the direction of the Lorentz force. It will be the vector product of the two vectors (0, 1, 0) and (0, 1, 1). Just by the earlier mentioned definition, which states that only orthogonal parts matter for both magnitude and direction, we already see that the rotating component of the B-field doesnt have any impact, as its parallel to the phi component of the angular velocity. And if you calculated the vector product you will come to the result that only the phi component of w and the z component of B matter, which result in a radial Lorentz force.
This radial Lorentz force moves charges from the middle to the outside of our plate, which creates a potential difference or in other words, it induces a voltage.
Im in the "theres nothing to rotate" club
This is one of the most genuinely scientific Action Lab videos I've ever seen. Normally they're just magic tricks that are supposed to be analogous to real concepts.
It sounds really suspicious when the youtuber paid to promote a product says “it has been found that the optimal health benefits are found at 3x the government reccomendations”
This is common knowledge. The recommendations given by the government are to prevent the most common disorders associated with each nutrient, not to optimize health or performance. The govt is telling you what you need to get a C-, while scientific research is telling you what you need to do to get an A+.
@@PeterSedesse i thought they meant x3 the reccomended *limit* which I found suspicious, but if it’s just the *get this much!* number then nvm
Do you trust the government? Do you not remember covid?
@@That.Guy. yes, the entire world conspired together, bitter enemies all agreed to fake a pandemic, Russia, Iran, North Korea all stepped up and helped Trump fake everything....sarcasm..
@@That.Guy.do u trust ppl trying to sell u products?
Now I understand, thank you for the demo. The circuit drags, then jumps, then drags again.
When the magnet is placed on the disc and they both spin together, the Voltage you measure is produced in response to the amount of Resistance offered by the closing circuit (metal brush) that crosses the field and if the brush were a different size the voltage registered would be different accordingly. But most importantly, it's about what location (where) in the circuit is offering the resistance to do so and the fact that the location in question offers an amount of resistance that is different from the resistance offered (at the other metal brush) so on essence you have a conversion from Potential to Kinetic energy at a location that offers Potential Difference. It's the potential difference where in this case the Resistance is the phenomenon that can help to expose the Kinetic energy being registered in Voltage.
Change the type and/or size of those metal brushes, surely the resistance that does this will change and so therfore so will the amount of Voltage measured.
1/3 of this video is a commercial?
Please would you show us what happens when the wire to the centre of the disc goes straight down the rotation axis ?
It will happen the same, and you will see paradox is still unsolved!
I think that the problem might be that magnetism is being viewed as an instantaneous force rather than something that can have or give objects inertia/momentum.
I think that the magnetic field needs to be cut simultaneously to produce voltage, so when only the magnet is spinning the magnetic field is not being cut and when the magnet is placed on the disk it is being cut by the wire brushes under the disk.
There is one other aspect that you can explore. In most motors, when you energize them & they rotate, if you apply load to the motor output, unless the frame of the motor is fastened down, it tries to rotate in the opposite direction. In motors with multiple magnetic poles, this "recoil torque" is against the magnetic pole structure. But for the homopolar ("same pole") motor you demonstrate, this does not happen. The recoil torque occurs against the stationary part of the circuit, not the magnet.
So you can do this demo: Motor rotor is on bearings free to rotate, as per convention. But also, the magnet & the "stationary" part of the circuit are mounted on bearings. When you power this up, the magnet remains stationary (held by the unavoidable friction) while the "rotor" & the "stationary" circuit rotate in opposite directions. For the demo, you can avoid another set of sliding contacts by mounting a battery as part of the "stationary" circuit. Manually spinning the magnet has no affect upon the motor's characteristics, not will any torque be borne against it.
I saw on your website that you were working on a book titled "Quantum Faith: A Quantum Theory of God". I would be very interested in reading such a book if/when it gets completed. Your channel rocks.
Surround the magnet with a mumetal shell so the field doesn't go beyond the spinning disk and see what happens. Like others have said, the magnet is inducting voltages in the wire/brushes themselves. Spinning it one top with a drill creates equal, opposing voltages on each side and thus the reading ends up at zero still (-1v + 1v = 0).
4:55 this is because the electricity is moving between the two wires (left to right) in the video irrespective if the disc (bottom) is spinning or not. Right?
What we can deduce from the fact that both voltage events occur when the disc spins, is that the magnetic lines of a circular magnet don't inherently change with its spin as no polarity change occurs.
The rectangular magnet would not behave the same if spun as the polarity would move the magnetic lines.
The way to check this would be spinning the magnet in a gyroscope and seeing if tilting the magnet along its polarity would cause voltage to occur, I suspect it would.
I did a video on the solution. It is the d orbital that causes the magnetic field. When you spin the magnet it does not change the velocity of the unpaired electron. That is a fixed energy. It's quantized. It can't change no matter how fast you rotate the magnet.
I want to see more experiments.
1) the wire at the bottom: make it perpendicular to the disk itself by extending the disk holder, thus eliminating half of the wire from equation.
2) rotate a magnet above a wire.
It's wild to think about just how many devices/components rely on that principle. Speakers/microphones, motors/generators, transformers, inductors, capacitors, antennas, relays... and I'm sure there are more that I haven't thought of. All of them are based on electromagnetic induction.
Excellent demonstration! I have seen one or two other videos but it was much easier to figure out what the paradox in this one.
You’re getting voltage when you rest the magnet on the disc because the disc itself, due to the direct contact with the magnet, is then part of that magnet and you’re inducing the voltage because the two wires that complete the circuit are stationary. The one with the positive lead is where the flux lines of the spinning magnetic field pass by and induce voltage. Its just not doing it where you expected it to.
I probably would not use an electric motor for motion as that complicates the fields ,a manual rotating disc will help with computational theory
Should be mentioned that round magnet is isotropical for rotation: one face N, other face S, centred rotation does not create field change (case 2). Should be specified the material of the disc, iron alloy or non-ferous? Is it perfectly isotropical for rotation? (e.g. a radial bolt beneath, to block it on the electric motor shaft, make it non-isotropical). This could change the field when rotating, IF magnetic field exists (case 1). The magnet left on the disc is eccentric, rotating it the field changes )case 3). If magnetic field changes, induction occur.
Path of least resistance to close the circuit generates a Sudo wire through the disk. The "wire" and flux must have relative motion to generate a voltage.
I think the field rotates and gets projected centripetally outward possibly in accordance to a phi like ratio as the two fields are perpendicular to eachother pertaining to electric and magnetic and vacuum allows for eddy current flow from the centripetal force at hand pulling in surrounding electrons via the magnet and conductive plate in a vortex type manner. Just like wind and running water contain ions and being diamagnetic/ dielectic in their nature. Same aspect I believe...
maybe test to see if voltage oscillations on the center and radial edges with oscilloscope/multimeter or thermal imaging... Nice work
I believe the field could have a slight flat planar toroidal resemblance in shape projecting, increasing rotation speed may increase voltage if theory is correct but at centripetal rate, voltage will max out and stabilize due to its available surface capacitance, and heat will increase and result in curie breakdown, thats the thoughts I was just given
the choice of using an aluminum disk is a curious one since passing a field through aluminum creates eddy currents that resist the changing field and trys to stop the field from passing and although aluminum is an electrical conductor it isn't an ferromagnet conductor and would not work as a transformer core.(for example) passing the wire in front of what is surely a magnetic pole does indeed induce a voltage in a wire as long as the field is changing (as in moving) and as soon as you stop it the voltage drops to zero, you will find the same effect if you bring the wire towards the face of the magnet and then away in a straight line. The most effiective way of demonstrating the generative effect of a magnet would be to wrap some copper wire around a bar shaped piece of steel then moving one end of the steel towards on pole of the magnet then quickly moving it to the oposite end thus alterating the polarity of the fields (what happens in an electical generator) thanks for your attempt to educate which is a whole lot better than most of the b.s. that's on the tube
Great video and interesting presentation
5:22 remove the disk, then spin the magnet, that will produce electricity not? The disk is blocking the spin effect of magnetic disk's fields, that's why it only generates electricity when you put it on the disk, because the magnetic fields are then generated by the disk as the magnet, in contact with the disk, transfers it's magnetism to the disk effectively making the disk a magnet
When the magnet is just above the disk, the "wire" is the size of the disk (which is bigger than the magnet), so spinning the magnet above it will generate no electricity, because the magnetic fields never cross the wire (so from the wire's point of view the magnet is stationary). So it would be the same as holding the magnet stationary above the wire and spinning it would not make any difference as the generated fields will cancel each other.
Just an idea
What if you spin both the magnet and disc in opposite direction, would that be the same as spinning the disc twice as fast
That's worth of a experiment.
Almost from the start of the video, I was saying "no". Took me a while to figure out why. Decades ago in physics classes, we had a 3-finger rule: Force, magnetic field, and CURRENT.
Think of static electricity, or a battery. You can have a voltage, with no current. That's NOT what happens here. It's the current that causes the voltage. Or has physics changed?
As for the setup: get a longer axle. 50cm (18 inch) should be enough. That way, the wire touching the axle should be well away from the magnetic field, and not affected.
And to see if flux lines are moving, try a container full of ferrofluid.
I observed a couple things that I have questions about. 1. When the drill was rotating does the direction matter? 2. Would suspending the magnet, from a rope or string make a difference if rotating? In either direction while the metal is also spinning.
When the magnet is rotating the magnetic field is not rotating due to uniform shape and density of the magnet, it still goes from north to south of the ring that could be up to down (or vise versa) in this case. so it only induct current when disk (its atoms) are moving through this field.
But if the magnet was not uniform in shape or density or if you rotate the magnet in another axis then it inducts current.
Why not make that wire touching the center of the disc vertical and retest to solve the paradox?
my theory on the both discs moving: it's not the rotating magnetic field that induced the current but the interaction of the disc taking the current path through the disc and moving it to keep the electron interaction high enough to read. basically I'm guessing the magnetic field knocks electrons loose and that creates the voltages, but also knocking into atoms knocks electrons loose and magnets help make more electrons come off while moving the disc causes them to move through the magnetic field in disc through the wires. I'm pretty sure it's something to do with the magnetic fields interactions with the nonferrous metals induced magnetic field being dependent on the connection points and the magnetic field in the rotating disc is only ever there when the disk is spinning. A couple tests might be to spin the disc and the magnet in both the same direction and opposite directions to confirm or deny the hypothesis that the line the electrons take, that line has a counter rotational pull to be in the line of the shortest path. meaning the same direction might not produce less than expected. if that fails then maybe something like the path is wound around as the disc spins like a swirling pattern similar to mixing food coloring into a liquid. it's not about if the field moves or not it's there's a problem that defies what should be so what's the reason is basically all this was for me
Field lines are things...the iron filings trick shows us that. Rotating the magnet would move the filings. Cool demo / good video as always
I’m really curious about why exactly a current flowing through a straight wire creates a circular magnetic field around it. I understand magnetism as a relativistic effect of the electric field, but not why the magnetic field is circular! Please some experts give some insight here
This does not subject to Faraday's Law, but is Lorentz force law.
When the disk rotates, the free e- in the metal disk also gets a net velocity that tangent to the circular orbit of the disk. With a station Mag-field perpendicular to the disk, it create a radial Lorentz force that makes the e-flow from center to boundary or vise versa depending on rotation direction. Thus creates a DC voltage.
The voltage only generated depend on the rotation of the disk, not the magnet, assume the magnet have a perfect symmetry.
There should be ionizing efect of ultra high speed very strong magnet on dipole ions. That means, although there is no voltage on entire circuit, there is emf on every segment of the circuit and some secondary effects shall be observable when the field is rotating.
Are we sure the electrons on the disk are still moving in a straight line during disc rotation? Is their movement influenced by the magnetic field and spin?
The Faraday Paradox refers to a curious phenomenon in electromagnetism where Michael Faraday discovered that when a conducting loop is moved in a uniform magnetic field, there is no induced electromotive force (emf) in the loop if it is moving parallel to the magnetic field lines, despite the change in magnetic flux. However, when the loop is moved perpendicular to the magnetic field lines, an emf is induced.
This paradox can be understood by considering the forces acting on the charges in the wire. When the loop is moved parallel to the magnetic field lines, the charges experience no force due to their motion, resulting in no induced emf. However, when the loop is moved perpendicular to the magnetic field lines, the charges experience a force due to the magnetic field, resulting in an induced emf.
The resolution to the paradox lies in understanding that it's not just the motion of the loop that matters but the relative motion between the loop and the magnetic field. When the loop moves parallel to the field, there's no change in the flux through the loop, hence no induced emf. But when it moves perpendicular to the field, there's a change in flux, leading to an induced emf.
Faraday's law of electromagnetic induction explains this phenomenon mathematically, stating that the induced emf in a loop is equal to the rate of change of magnetic flux through the loop. So, there's no paradox, just a misunderstanding of the conditions required for electromagnetic induction to occur.
Isn't the answer much simpler that you only get a current if the charges in the disc that are free to move will experience a force due to the 'stationary' magnetic field. The magnet is rotationally symmetric so there is no change in the B field in time. But the negative electrons in the conduction band of the metal experience a lorenz force when they are made to rotate through a stationary magnetic field so they experience a lateral force creating a potential across the circuit. All that matters is that the disc is rotating because that is where the free charges are that will be moved.
If possible can you try an experiment that I came up with. The things you need are an empty room, a light source and you inside the room. What I have in mind is that , when the light source is turned on you are able to see the walls of the room because they reflect light from the light source. But what if we make the surface of the walls so imperfect that in whatever direction light may hit the wall it does not get reflected to atleast a single point in the room. Which means if you observe the room from that point, even if there is a light source in that room, you would not be able to see anything like the wall and the ceiling in the room.
Hi friends.
At the first time, i didn't understand but now, it is clear:
When the magnet was rotating on this axe, there is no variation of the magnetic files due to motion of the mouvement of the magnet.
While making rotating the magnet plus the métal disc, there is the Lenz force, because of the magnet.
No problem, just the reverse induced by the move...
Isnt'it?
You speak, and i don't understand.
It's so clear, just Lenz force, while same effect if the magnet is turning or not. Look at the pôle of the magnet, it is or north, or south. Just à magnetic field and a metal disc in move> induce à current in the disc.
It is called lenz force.
What if a magnet rotated with the drill and disc also rotated (with the same speed as of drill in its direction)does we can get any Volta?
Can you guarantee moving the magnet that way also moves the field lines? Spin it on it's side would probably work.
Think path of least resistance.
When the magnet is in rotation with the disc there is no circulation of current induced in the disc, instead the magnetic field induces current using the path of least resistance across the disc to complete the rest of the circuit.
When the disc is stationary and the magnet is motion, the induced current still follows the path of least resistance, in this case, rotating around in the disc itself, the rest of the circuit is of higher resistance and thus ignored by the current flow.
in the magnet spinning only , there is no virtual wire . the electrons are instead displaced by the magnetic field about the conducting disk as they get from the pos to the neg brush
Thanks! I have a PhD, in physics, but i did not see such a simple explanation of this experiment! Maybe if we used resistor underneath the rotating disk of the centrifuge as part of the circuit and measured the current in it by measuring the voltage drop on this resistor everything could be demonstrated more explicitly.
The field has to be stationary that's why when only the magnet rotates there is no voltage but when the disc rotates with /without the magnet the disc moves through stationary field making voltage.
Love your videos. Keep 'em coming!
I wonder if your metal brushes, stationary as they are, when your aluminum disk spins, are the brushes disrupting electrons in some manner so that when you drop your magnet on top the spinning disk so both spin together, the electron situation, if any would be caught in the magnets field and be the cause of the voltage readings.
Eddy current in the alluminum disc?
Perhaps with the magnet stationary it has time to emit its field lines, so with the disc spinning, the wire brushes and the aluminum disc catches the em field (voltage). When the magnet spins, it does not have enough time to emit its field lines (no voltage), so when they spin together they are relaying its field lines in sync (voltage).
yea right.. btw in order to generate electricity by messing up w the magnet, u will have to continuously change the intensity of the magnetic field..
Yeah, as an electrician this feels like it'd be pretty easy to work through. If you have a voltage you're cutting field lines with a conductor...I tend to side with physics and would just assume it is not immediately apparent where that is taking place. You have to be aware of whether you are producing a DC or AC current, and make sure your meter is setup appropriately.
The second one is easy to explain. The points at which you're attempting to pick up the current aren't changing. If they were rotating around the metal disc at the same speed as the magnet, you'd get a current.
And I agree with deusexaethrea for the last one. There are other areas of the circuit which are electrically conductive so you're introducing a moving magnetic field to them which is producing the current.
"Two circuits one field"
The electric circuit can be seen as being made up by two sections of wire.
Section A is the stationary circuit being the instrument and the wires to the stationary contact points at the center and the peripheral of the disk.
Section B is the circuit on the disk between the contact points.
At all times when there is a relative motion between the disk and the magnet a voltage is induced in section B.
At all times when there is a relative motion between the magnet and section A a voltage is induced in section A.
The trick is to observe that A+B makes up a closed loop but the motion of the conducting parts relative to the magnet differ. When both are moving in the field the voltage cancel out. If they move with different speed there will be a non zero loop voltage.
When the magnet rotates and all other parts are stationary the sum of voltages in A and B is zero. They are not of the same amplitude and opposite sign, but they entire loop cuts the field lines twice. The flux in circuit A+B does not alter. All flux that enters the loop A+B, exits at the same rate.
When the magnet and the disk rotates in conjunction there is no voltage induced in the disk and no voltage in circuit B. But the magnet field lines still enter and leave stationary circuit A.
When A and B was both subject to a rotating magnet field the loop voltage cancelled out. With the disk is moving with the magnet, B is in a stationary magnetic field the, flux encircled by circuit A + B is no longer constant.
As B resides in a stationary field and A is in a moving field the loop voltage does not cancel out. As B is not exchanging any flux, but A is, the loop A + B flux is in constant change.
Best channel ever! I love action lab!
Truly Amazing Bravo 👏 (ps: your talent and expertise still amazes me I mean for a youtuber you just exceed!)
with the spinning aluminium disk you're generating a voltage because it's crossing the part of the circuit on the left side view, the side where the larger brush is, between that brush and the small brush. the closer section to the camera view
it's not a paradox at all. in the "non-functional" example, you're not not breaking field lines. to generate voltage in a wire in a field, u have to break them, that's why the disk itself is the exception.
Isn’t it because the wire is officially connected to the center axis of the disk? Therefore the circular magnet field is not actually passing over the wire to complete the circuit when it rotates around the center axis?
While you used a circle magnet does this process change at all with the bar magnet you showed later in the ep knowing the bar magnet field rotates?
I’m curious about something what happens if you rotate the magnet the opposite direction of the spinning disc? Does anything change? Something like getting negative voltage?
I think the idea of magnetic feil lines comes from the fact that we use iron shavings and 2D methods of viewing a magnetic field. What you are likely seeing is that the magnetic field is less like a set of lines emanating from the magnet and more like a set of shells. I say this because the second experiment with the magnet on a drill has the magnet barely moving but very quickly rotating but the third experiment has the magnet on a spinning plate not perfectly centered causing the magnet to move back and forth making a small current
Isn't also that not the complete disc is acting as conductor, but the biggest portion of the current is going through the shortest line between the two brushes (this path is acting as a virtual stationary wire), thus there's a relative motion between the wire and the rotating magnet?