Nicely done. i was tired of TLDR versions that basically drop a neodymium magnet inside a copper tube. At last a comprehensive explanation that even in physics lab classes at college level is sometimes overlooked. Very well done.
My dad had some small, powerful magnets, and it was fascinating dropping them down the tube of an aluminum foil roll. It was like magic how they slowly tumbled through.
Awesome video! Demonstrations I've never seen before. This has a real world use familiar to coin collectors. Magnetic slides made of rare earth magnets are used to test coins. A silver coin will drop slower than one made of copper or brass. It's a great and quick way to test for counterfeit silver coins.
Historically, a mechanical speedometer had a magnet rotating in close proximity to an aluminium disk. The ability of the disk to continuously rotate, was restricted by a spring, so as speed increased, the pointer attached to the disk would only turn as far as the tension exerted on the spring, thus indicating road speed (plus around 10% due to a legal requirement 🤣). (An early "Smiths" clockwork speedometer, worked without magnets, possibly due to patent requirements)
My lil cup bearings gummed up. Spray it with wd40 on the odd occasion i felt like digging, have a speedo for a week. My new bike? No abs, no speedo sensor... its on the engine speed, like most cars etc run off the gearbox. Means i cant change sprocket ratios :( Hate new stuff. Gimme things i can fix!
Always a joy to watch new stuff from you! 🥰 Do you have any plans of exploring superconductivity, or would that be too financially and safely intensive/complicated to try?
Back in the day we were decommissioning a 7T superconducting magnet so I took the opportunity to stick a chunk of aluminum into the bore and that was a lot of fun. Also when in service pushing the evacuated metal tube of the FT-ICR into/out-of the bore was an exercise in patience, but a free hand-held aluminum block was a more dramatically weird feeling.
@@fabianradakovitz9064 True, but its not that much used because of weak mechanical strength. But we already have a solution for that with alu conductor steel reinforced cables.
I first realised this effect when, as a kid my Dad would let me loose on a pile of old scrap cars, and armed with screwdrivers, pliers and an adjustable spanner, I would strip out all the jewel lights, switches and gauges. I stripped out many speedometers and discovered that the cable turned a pair of magnets on an armature which were in very close proximity to an aluminium disc which had a clock-like spring attached to it and also the indicator needle. Fascinating! That was 53 years ago, now!
I have no idea why some German soda cans are made of steel... They are all made of aluminium in Denmark. But you're right, they are (all?) lined with a lacquer to prevent chemical reactions. Thanks for the early watch!
Since the 1935's all cans were made out of sheetsteel (iron with a bit of carbon) if I recall correctly. Mostly due production capability's. In 1965 aluminium soda cans were slowly introduced.
The last time I encountered steel soda cans was in the US Midwest in the late 1980s, a generic supermarket brand used steel cans, and seemed to transition to aluminum by the early 90s.
@@guyh3403 I assume then that the current supply comes from someone using old production equipment that hasn't broken yet. I once tried to understand which material is cheaper and why. I _think_ what i found was that raw iron starts out cheaper since it is more abundant, but aluminium is much easier to work with, so the more refinement steps there are in your production line, the cheaper it becomes to use alu over steel.
QUESTION... The last experiment, using the three samples are affected by the weight of the samples, although the copper and silver are similar in speed despite a weight difference. Could you try in a future video using the rare earth magnet on a pendulum between two blocks of silver/copper/aluminium to see the eddy current braking effect when the moving item is the same between them? The gravity effect is cancelled as the moving item is the same, but the density of the metals would be different (as well as the conductivity). GREAT VIDEO BY THE WAY!!!
The floating on water experiment might not work that well. The styrofoam usually gets "attracted" to the edge of the water by itself. I believe it's because of waters surface tension
Excellent vid. When rolling the cylinders, did anyone notice an increase in speed through the centre of the magnet, and only a slight decrease in speed on the trailing edge. (I'm thinking this was due to increased momentum through the centre)
I am here to judge RU-vid's recommendations Good background music Good voice Decent visual examples Very slow video that only covers one or two simple concepts 3.5/5 Worth my time
So cool. Ive always been fascinated with magnets since i was little and they still leave me in awe. Your videos are so valuable. I love learning new things. Thanks for this and i cant wait to see more!
I have absolutely never in teaching physics for about 15 years heard that it would be a "common misconception" that eddy currents would always cause repulsion. The idea that opposing (in Lenz's law sense) would get mixed up with physical repelling is something new to me. :S Is this a cultural, local or language thing? Has this misconception been studied in scied publications?
Excellent video. I haven't seen any stainless steel soda cans but now I will pay attention. I've seen another video quite some time ago where the vlogger demonstrated the diamagnetic properties of a MOUSE - a real live one.
@@brainiac75 that got me to thinking, those should fall slower, then I realized the upper part of the ring is a lot farther from the magnet, and so the square law is raining on the parade. And THAT got me to wondering just how much the diameter of the cylinders is affecting the test. Someone in another comment asked about racing an aluminum cylinder of the same WEIGHT as the copper one, and that's what I was thinking... the larger diameter should lower the diamagnetic repulsion farther from the magnet? But I think at that point the math is getting very ugly and a plain test would be the fastest way to get an answer. Maybe if the LENGTH of the aluminum rod was made bigger without changing the diameter? But THAT got me wondering how things compare at different places on your crazy magnet. It's strongest in the middle right? So a long cylinder may not be fairly compared to a short one?
En ting jeg altid har tænkt på er: Hvor og hvordan i alverden opbevarer du dine store magneter? Fordi de helt store magneter må da kunne give problemer med andet elektronik eller lignende. Elsker at se dine videoer. Bliv ved med det :)
I nogle store kasser, så man ikke kan komme helt tæt på dem: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-yM4Xe2c0B8M.html Magnetfeltet aftager meget hurtigt med afstanden, så de er relativt harmløse på omkring halvanden meters afstand. Flere videoer på vej. Overvejer at lave en kasse med magnetisk skærmende mu-metal plader indbygget ;)
@@brainiac75 Spændende. Kunne ellers godt forstille mig at det havde været farligt hvis de ikke var pakke godt væk. Men det lyder også som en god ide med nogle kasser med magnetisk skærmning. :)
@@brainiac75 I've wondered if it's possible to build something like a Faraday cage but for magnets. I did some reading, and it does seem like you can use a metal box to "guide" the magnetic field lines, limiting how strong the magnetic fields are outside, but not to the same degree as a Faraday cage can with EM radiation. I don't have a solid grasp on the physics of it though, so I'd love to see any video you make about your experiments with storage boxes for your magnets!
I anticipated the aluminum would move slower due to the higher resistance dissipating more energy as heat, but it being lighter also makes sense. edit: Now that I think of it, acceleration due to gravity isn't typically determined by weight, so I'd like to see these things fall in the presence of a magnet perpendicular to the ground.
Under idealised circumstances (steady state, which this isn't, but it's very close) the energy dissapated by inducing Eddy currents is inversely proportional to both resistivity and density. So while the aluminium has higher energy dissapation, it's not to do with it having a higher resistance, as that actually reduces the energy dissapation. In this case the braking effect is inversely proportional to the square of the density: one factor due to energy dissapation and one factor because of decreased gravity.
@@JoQeZzZ Thanks, for the explanation. I was just rewatching the video, actually looking at the calculations circa 11:00 and seeing how my expectations were completely backwards.
I had forgotten that silver was more conductive than copper. Silly me. Your big magnet seems to have magnetic bald spots or lacks uniformity. All 3 samples wiggles around the middle.
I remember in high school physics when the teacher had an AC coil at the base of a 1m steel rod perpendicular to the demonstration table. When he placed an aluminum ring around the steel rod it fell and rested on the top of the coil. When the power was switched on the ring rose 15-20cm off the top of the coil and danced in the alternating field. And it got quite hot.
Magnets are just fascinating... I never get tired of playing with them. I've spent countless hours trying to wrap my head around how they work. I'm convinced that whenever science can completely explain magnetism the worlds energy problems will be solved.
It's a pretty good video, but you could do another video on electromagnets, including one the scrap metal recycling industry uses to sort even lead. Covalence fields tuned to a particular frequency can attract specific metals, including gold. It's pretty nifty, mostly used in scrap yards to sort large quantities of different metals from each other. Also used when a steel mill is processing incoming metal bales to pull out the metals that can be attracted to them.
Similarly, I read before about an electromagnet called the master magnet that could attract any metal. It was simply an electromagnet with a copper disk attached to its face.
Why should density affect the rolling speed? Both the gravitational acceleration and the rolling friction is independent of density. Could the difference be due to the surface texture?
There are way too many people out there, that are completely oblivious to the fact that in addition to magnetic (ferromagnetic) and non-magnetic materials, there is also the existence of diamagnetic, and paramagnetic elements & compounds. There is a whole world of exciting things to explore, more than one person can ever experience in a lifetime. There is no time to waste!!
<a href="#" class="seekto" data-time="264">4:24</a> Do you have a measureing scale to put below the magnets? Does it's weight change while slowing down the aluminium plate?
I don't know what the deal is with Pepsi cans, but they have been using steel for 30+ years. We used to pick up cans to take to the recycler when I was a kid, and the conveyer belts at the recycling facility had strong magnets on them to attract and discard all the Pepsi cans. I think there were other brands, but everyone knew that Pepsi were no good for recycling (for aluminum prices anyway).
You might. Say you're designing something that is inside of strong magnetic fields, or being careful that your aluminium can doesn't melt into molten aluminum when it's near an inductor
You should try a ratio of the densities beginning with the inclined magnet angle for the slowest time to roll off, and multiply the ratio of one greater density to the lesser or least density and multiply that ratio of densities times the angle of the slowest time, tilt the magnet incline to that new angle and see if the densities roll off the incline in the same amount of time each.
Silver is the most conductive to electricity and will have stronger eddy current effects in it when exposed to a powerful magnetic field. I wish it was used in home electrical wiring but unfortunately it's not as cheap as copper. I thought silver would be the slowest to roll of the neodymium magnet, odd
Every time I hear the word eddies all I can think of is this "'Eddies in the space-time continuum.' 'Ah...is he. Is he.' 'What?' 'Er, who is Eddy, then, exactly?”
<a href="#" class="seekto" data-time="79">1:19</a> German export goods, I live near the border and it is amazing how many danish people cross the border to buy alcohol, sweet and fatty stuff due to the high taxes on it in Denmark. Thanks for supporting our local economy :D
Hehe. Glad to help, but I live too far from the border to save money on it after trip costs (unless I need very large quantities) but a friend left soda steel cans after a party at my house. Very useful for science videos ;D
I love the effects of magnetic eddy currents Lol *I wonder how the electromagnetic force behaves in space, on massive scales, and really small scales?" Maybe we don't understand how massive things the scale of Galaxies behave? *I really wonder if Electromagnetism plays more of a crucial role in many different aspects of the Universe then we currently understand? Gravity, such a important aspect of nature yet seems like we don't understand "all the details about it yet" (In the form of a analogy) it really does seem like aspects of Gravity share similarities with the electromagnetic force. -Like Static charge's act upon small dust particles & allow them to acquire mass to begin gaining density. We can't have light/radiation, electricity without the electromagnetic force. The strong nuclear force seems to share similar charge behavior as well, so does chemistry. It uses +/- charges to bond compound's. I wonder if these aspects of Nature have more of a connection than we currently understand? Maybe things on different levels, strengths, size's, scales, could alter the behavior of a force we already know about. Maybe just certain things are needed, Such as temperature, density, pressure, velocity/rotation, energy/frequency/vibration, viscosity, etc. Think of how star's are created after enough mass is acquired? Radiation, light, magnetospheres, rotational velocities. They all are so crucial to Nature and all require aspects of the electromagnetic force for it to even exist.. look at a graph that shows the levels where different materials transition into different states of matter: maybe their are threshold points of (density, rotation, heat, atmospheric pressure, etc.) It's just a gut feeling I have after watching tons of science videos covering the behavior of the Universe around us. (the only way we can obtain growth and learn the things we are right about and the things need slight adjustment on? Is to be willing to allow ourselves to be open and thinking from all perspectives even on things we think we already know about.
I appreciate the lengths you are going to to explain what is going on, using all manner of arrows and other symbols. I'm still having some trouble grasping it. Another viewing or two might do it. I think oxygen is paramagnetic, so we ought to be able to set up a device that uses magnetism to collect oxygen, right? Right? Hello? These quantum phones aren't very reliable ye [signal lost]
I have a question, is there such as thing as an electromagnet that can be purchased anywhere on the internet that can pickup aluminum, specifically an aluminum can? I know that some garbage dumps have special eddy current separators that cost tens of thousands of dollars, but I am looking for something that is small that is battery powered, or can be powered with 120 AC, or with an AC power supply that can pickup a can. Does anything like that exist? I already found electromagnets on the internet that are cheap, and they use AC instead of DC, but I have no idea if they work on aluminum. Maybe such things are not possible to create?
You could have added a metronome to the background (or a clock) to show that the footage really isn't slowed down 😄 (I still believe this video though, as I have seen these effects in real life 😊, e.g. letting a magnet fall through an aluminium tube)
Well I think, the idea is to look at the forces on the cylinders. If you use a very basic model for the friction (lets say it is equal to the normal force to the surface times some constant) we could say the the accelerating force is sin(a)m*g (a being the angle of the magnet, m the mass of the cylinder) and the force due to friction is some friction constan b times the normal force = b * (m*g*cos(a)+ c*v). c being some constant for the specific material (due to conductivity, v being the speed at which it rolls down, rememberg that the current depend on the change of magnetiv field and only occur when it rolls). Alltogether we got something like F_total= sin(a)*m*g-b*(m*g*cos(a)+c*v). Now you can see that, if you divide by the mass to get the acceleration, the "negative" acceleration from the eddie current is proportional to c/m. With smaller mass it gets larger and with bigger conductivity it gets larger. Since the factor by which the aluminum is lighter then copper and silver is bigger than the factor by which its conductivity is smaller, you see what you see. Sorry if this is not very compact :D
Aluminum, copper, and sliver not magnetic metals but still have an effect by magnetic due to eddy current effects and Lenz law. It's pretty cool that those metals are not magnetic but still have some effect by magnet. Wondering titanium and tungsten have same effect like Aluminum as those metals also not magnetic.
Would you be interested in a (semi) DIY gamma spectrometer? Saw your radioacitvity-related videos and I liked the Radiacode-101 review, so I think this would be a possibly fitting video ;)
I would like it too - but I don't have a 20x10 mm gold cylinder to compare with. I don't know if anyone makes one - at a cost I can afford ;) Thanks for the early watch!
Hm, not sure. If it was just longer to match the weight, it would likely roll at an unchanged pace. But if its diameter was larger to match the weight of the others, I think it would roll faster, because more of it would be in a weaker magnetic field farther away from the magnet. An alu soda can rolls of the magnet quite faster...
@@brainiac75 What if it was the same proportions, but larger to match the weight. Is the soda can empty? If you mentioned if the can was empty, I missed it. I am not really going anywhere with these questions, I am just curious. Eddy currents don't make sense to me, for lack of a better analogy, magical, or property biased, viscosity makes more sense to me.
Isn't there also a golden spot in internal resistance of the material, so aluminium is a bit worse conductor than tho other two, weighs less and that's helping it to roll slower?
noo! i was so sure it would be copper or silver, i didn't think about how light aluminum is. oh well! definitely will remember this the next time i hear someone say aluminum won't react to a magnet
How about if you move the magnets close to elements to see if when in a pushing movement what it registers on the scale and when pulling away if it registers it’s getting lighter.
