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Linear Magnetic Field

I am stuck in my research,please tell me a way to make a linear electromagnetic field,other than making an outer core for it please help me

Topic by ajose4    |  last reply


Magnetic field redirection? Answered

Hi, I've never seen a community so welcoming and intuitive than the instructables community, so I decided this website is the best place to ask my question. I'm sure there is someone hidden deep within the fathoms of instructables that is versed in the matter of magnetic field redirection. I'm working on a project that I will post an 'ible of, (truly wireless speakers ;)) but I need some method of redirecting a magnetic field so it doesn't interfere with the speakers. I have heard of some methods, i.e. Mu metals, MagnetShield, but these are not easy to come by, especially in the UK. I have considered ordering from the manufacturer, but I am not willing to pay the exorbitant shipping costs. I would firstly like to know if such a material exists, or if alternative/better/cheaper methods are available, secondly, whether or not it can be procured in the UK, and if so, where, and thirdly, proper application of such a material. I have done lots of research into the matter, but have been left fruitless. I'm sure someone can help.                                                                 Merry Christmas,                                                                                             icyseptember

Question by icyseptember    |  last reply


Make a magnetic field detector ?

I dearly want to make a device to measure electromagnetic fields in the house ,since the presence of such has been more than obvious and at times annoying . My CRT monitors behave strange in my room . The geometry of one bends as i turn the monitor in one direction and at the same direction ,my spare one changes color to blueish like pale . Interestingly, they do it in the same direction no mater where i put them in the room . My turntable's (i am in to Hi-Fi gear ) cartridge reacts when i put it in some places in the room and i hear noise come out of the speakers until i reposition the turntable . Anyone have any ideas how i can locate the source ? Some simple device ,or schematic that will give me the ability to measure ,or at least detect to some degree the fields responsible ? Will be thankful for any answer .

Topic by soundsmyth    |  last reply


Long range magnetic field?

Hi,right now i am stuck with my research.I want to make a long range magnetic field 14 m (approx) please help me 

Question by ajose4  


Magnetic Field for hollow core?

I am working on a project in which I have to control a small setup at the end of a motor shaft using an electromagnet. The electromagnet needs to be around the shaft inbetween the setup and the motor. So I have used a metallic ferromagnetic spool(image attached) and wound 32 gauge wire on it to make it an electromagnet and put the shaft through it. Since this core made out of spool is hollow, I'm not sure how the magnetic field will behave. I tried powering up the one I made and it' seems to be both attracting and repelling a magnet's pole (edges attract while centre somewhat repels). Anyone got any idea about this?

Topic by Antzy Carmasaic    |  last reply


Waveform of pulsed magnetic fields... Answered

I have recently been astoundingly interested in magnetic fields, for seemingly no reason. The point is, that in reading up on it, and being a big fan of the greatest mind of all time, Nikola Tesla, I have been stumped with a question that I can't quite seem to answer, and can barely wrap my head around. My question is this; when one takes a normal electromagnet and sends pulses through it, is the resulting pulsing field considered to be longitudinal or transverse waves, or something else all together? This has baffled me, and I am curious to see the answer. Another question I have is, what exactly does Tesla mean by "hertzian" waves, I'm assuming that that his "non-hertzian" waves are longitudinal waves, but I could be wrong. A little background on the question... This question arose when I was looking at the 'ible "spooky tesla spirit radio"  (something along those lines, I'm not sure the exact name). I read somewhere in the comments section that Tesla found Hertzian waves to be, for lack of a better term, a waste of time. This brought the question of different waves up, and one thing led to another and here we are!! Thanks for any and all answers!!

Question by arhodes18    |  last reply


Electro Magnets

If an electro magnet is suspending something in an vacuum environment, will it act as a medium? (Will sound waves be able to pass through the magnetic field?) Thanks

Topic by Weissensteinburg    |  last reply


Is it possible to make the magnets lose it magnetic field permanently? Answered

I know magnets can lose its magnetic properties if exposed to heat, but is there a way to make the magnets permanently lose its magnetic fields?

Question by Plasmana    |  last reply


Magnetics software for designing magnet coils?

Dear Instructables, I need to design magnetic coils for a mattress that would emit a uniform magnetic field. Does anyone know of a basic program that would plot flux density over the coils? Preferably free! Thanks! Mike

Topic by Cburg1    |  last reply


how do you know the size of the magnetic field with respect to the amount of electricity?

For example you have an electromagnet and it has an electromagnetic field how can you know how much electricity to put to make a magnetic field with a specific size (like this many volts equals this many meters in diameter)

Question by HassanA32    |  last reply


Focusing Magnetism? Answered

Hi y'all! I am wondering if it is possible to focus magnetism? Like if you have a powerful electromagnet with a less powerful electromagnet wrapped around it. Then if both are turned on, the small one will focus the larger one creating a straight electromagnetic field and making like a "electromagnetic laser".  Thanks, joespicnictables

Question by joespicnictables    |  last reply


A little magnet experiment for everyone!

Some people just love to play with magnets and have a lot of them.If you are just like that and like to tinker a bit then I might have something for you.What magnets you use for the following experiment does not really matter but you should have 20 or 30 of identical properties.Can be disk magnets, block magnets or cubes, just not spheres ;)If you have a 3D printer you use it to make it fancy but a peice of wood, acrylic or such and a drill will do for round magnets.For cubes or flat packs you can make retaining walls on a flat surface.The experiment goes like this:I assume you already tried ways to combine your magnets to make them stronger, like stacking them up.But there is another way to really increase how strong they are combined.Start with one magnet at the center.Then like a ring add more magnets around it but with the oppisite side up.The created mounting solution is to prevent them flipping up and together, you want them as close as possible though.Add another ring and change the direction of the field again.Try this magnet, once all magnets are secured and compare the holding strenght to any other combo you tried so far.It will be much higher for the same amount of magnets.If you want to prevent the use of glue then try to create your mounting system with a really flat but strong enough bottom - this will then be the contact surface.Slightly reduced strength but you can re-use magnet with ease.But if you want to get a really strong one you need cube magnets.Like before you want to create some sort of grid, this time we go for a square.Start with cube in the center, facing north up.Leave enough space in your construction to add 8 more cubes around it - like on the face of a rubik's cube.Leave them empty for now !Add nother row, this time 16 to keep the square.Of course these one go with the south side facing up!Again one empty of 48 and then one last one with north side up with 196 magnets.Ok, to be fair, you wouldn't be able to pull it off a metal surface unless you used really tiny cubes, so if in doubt then go for just to 48 and leave the enter one out for now.Should be quite intense but similar to what any other shaped magnet would have done.Time to fill the voids!Add the cubes in the spce between the magnets so the north and south side face the magnets next to it!So basically sideways but in the correct orientation.You can then also add the center piece - try either orientation for that one ;)What happened now is that you forced the magnetic field lines to go up instead od for trying to go the easiest and shortest way to the next magnet.And "up" is where our magnetic surface would be, which provides the now overdue shortcut for the magnetic fields.Be amased how much stronger this version is and how much even 3x3x3 cubes would accomplish.With 10x10x10mm N52 magnets you might be able to use them support our wieght if you pull straight dwon from a horizontal surface...Ok, kidding, not just might, unless you are really big...One 10x10x10 might hold about 6kg.Stacked up a bit more but having 20 or stcked up would not be much stronger than 10.Even just 25 magnets with one in the center, one row of sideways orientated and one row with opposing field to the center one would be hard to remove from a steel surface.If we go with the imagined 6kg per magnet we could assume to get 25 x 6 = 150kg of holding power.Check you single magnet first then compare to the square of 25 ;)Consider using some plastic between magnet and surface so you can at least slide or pry it off if you have to.You can also combine magnets or a new one that has one side appear much stronger than the other.Meaning that for example on the north side it could hold 20kg while on the south side only 5.

Topic by Downunder35m  


Does the strength of the electromagnetic field of a coil depends upon the thickness of the wire? Answered

Whenever I have problems with the magnetic field strength of an electromagnet people tell to use a finer wire, I have some, its thickness is not more then the thickness of a hair, but whenever I use it, I have difficulty in connecting it with the battery because it's so thin it easily breaks off, and when I turn on the switch, it burns up instantly, maybe I am not using enough length of it. So does the field strength really increase with the decrease in thickness of the same length of the wire and same diameter of the coil, if it does than why?

Question by Wisaam    |  last reply


generating electricity?

Im am a novice at electics,  i think that a coil of wire through a magnetic field will generate a charge,  Yes/no?  if so would a number of coils passing through one magnetic field be more or less efficient than 1 coil passing through many magnetic feilds?

Question by QSDR    |  last reply


Can you charge a capacitor from the collapsing magnetic field of a coilgun? Answered

I was thinking about making a coilgun; not too powerful, only a small, compact (ish) version. Problem is, the capacitor takes a while to charge. What I was wondering is whether you return electricity from the collapsing magnetic field of the coil (after firing a shot) back to the capacitor, thus reducing charging time? And another thing; does a coilgun produce a weak EMP or something when it fires?

Question by .Unknown.    |  last reply



how to make a good relation between magnetic fields that formed by electric fields and magnetic force ?

How to make a big magnetic force if we have a Direct Current battery, a solenoid, a magnet?

Question by puteri salmiati    |  last reply


If a person can feel magnetic fields does that mean they have electromagnetic hypersensitivity? Answered

I want to know cause I have a reletive who can feel magnetic fields from magnets.

Question by nerd7473    |  last reply


PEMF device that mimics earth's magnetic field?

I am very interested in making a pulsed electric magnetic field device that mimics the Earth's own magnetic field. It could be as simple as one single coil. That coil would have to have a magnetic field that measures in the 30 to 90 microTesla range, and it would have to be able to be pulsed in the 5 to 45 Hz frequency range, since that is roughly the strength and frequency of the Earth's own magnetic field Any ideas on how to make that happen? I am a reasonably intelligent person, but I am not necessarily technically gifted. So for somebody this might be uber simple, I don't know, but I am just not sure how to go about doing this. What do you think?

Topic by lapis lazuli    |  last reply


Can any intangible thing manipulate electrical flow?

Like is there anything non-material, like a magnetic field which when brought near a wire or by any other way stops or allows the electric flow through it? And I am not talking about a changing magnetic field producing a current in the wire.

Question by Wisaam    |  last reply


Is it possible to make a magnetic field strong enough to prevent a gun from firing?

Is it possible to make a magnetic field strong enough to prevent a gun from firing, stoppng the moving parts from moving? If so is it possible to make it directional?

Question by Kyndig    |  last reply


Can you fill an entire room with a strong magnetic field using current technology? Answered

I had an idea, but it will only work if an entire room is filled with a magnetic field. I plan on doing this idea within 30 or so years, so you can take you time answering.

Question by The Mollusk    |  last reply


Magnetics software for optimizing coil design?

Dear Instructables, I need to design coils for a matress that would emit a uniform magnetic field. Does anyone know of a free software program that plots magnetic field strength of a coil? Many thanks! Mike

Question by Cburg1    |  last reply


magnetic field from a permanant magnet can it be blocked?

Original Question (Hi does anyone know of a material that will block the magnet field from a permenant magnet without the material being to thick.) Thanks for your replies, to go into more detail, the material must not be attracted to the magnet as would mild steel The magnet force/pull is about 1LB and I need a material less than 5mm thick that will reduce its pull by at least 10 percent but the higher the better. Also it must not cost a fortune, (How much does Mumetal cost and is it attracted to a magnetic force),  I have searched high and low and I am now begining to think that  my search is futile and maybe no such material has yet been discovered. Your my last hope people. Thank you.

Question by needtoknowmore    |  last reply


6th Sense Device (To Sense Magnetic Fields)

I saw a program not too long ago (I believe it was from the UK) about an experiment that was done in which they outfitted a participant with a device that contained a magnetometer, as well as some number of vibrating motors mounted on a belt along his waist. It was designed so that overtime, his brain interpreted this incoming data as a "new sense" which allowed him to literally FEEL the magnetic directionality of the Earth. I'd really like to try this for myself, but am no good doing electronics projects from scratch. (I need guidance)  So is there anyone here who is up to the challenge of attempting this, or can anyone at least show me how it might be possible to create this myself.  I'd love to augment my senses full time and become a super human. haha Thanks in advance for any and all help. -Nick

Topic by foxymcfox    |  last reply


Linear magnetmotor - the basics for a beginner

Designing what is said to be impossible can be tricky, so I will try to give you some tips to reach your goal a bit quicker.A lot of people these days try to start with a wheel.Makes sense in one way as the final goal obviously is something that would rotate.However, considering angles in a rotating system is far easier with a usable baseline!We developed the liear motor well after any rotating electric motor.But only because someone already invented it for us.Making it flat was then more or less about finding a need for it first, like the modern highspeed trains on a maglev principle.If you want to make something move then it makes no big difference if you do it in flat or round.Flat however leaves you more options and much easier adjustments.And you will need a lot of the later...IMHO the best size and option for linear is the N0 model railway system.Tracks are only 3CM wide and second hand carriages to salvage the wheels is cheap.Either way, how would you start?We have multiple choices, like single row of magnets or double, maybe even tripple.Same for the actual magnet orientation.Flat, angled, attracting or repulsing...They all work if you understand how they actually work.Not the principle, the magnets ;)You see, a magnet always has two poles and without trickery both poles will be of even strenght, size, angle to each other and so on.Playing on a small and flat track with little resistance allows to use tiny magnets, like 5mm disc ones.If you follow the common concept of two magnet rows either side at a slight angle then you are half way there.People spent a lot of time trying not only to let the cart being attracted by the first magnets but also to let them pass out at the other end.In case you wonder why:Being able to be "sucked" in means you will have some force pulling on your cart from the next stage.Being able to fully pass through and preferably gain speed, means the cart would go from one set of magnets to the next - motion is accomplished.Let me give you my personal favourites for 5mm disc magnets:1. The rows are at an angle of 4-5° like a slim V-shape.2. Same as above by with the orientation changed by 90°The first basically means you have the magnets facing up while in the second you would have them mounted vertically.Both have good and bad sides and I think it is easiest to start with the first option.Here you would have a row of magnets at a slight angle either side of the track.Lets say it is all pointing away from you, then the north row would be left, south row on the right of the track.If you start narrow or wide depends if you want attraction or repulsion forces to work with.Again, it makes no big difference really, just a different way of operation, most seem to prefer repulsion though thinking the forces are greater - this is not true though ;)A very often copied way of mounting the working magnet (s) on the cart is by placing a magnet with south facing down on the left and one with north facing down on the right of the cart.Here you have the big problem of manipulating fields.The forces are quite strong and it seems the obvious choice but should be left for the advanced classes.Let me try to explain:No matter the site of your work magnet it has a very narrow acting field.Means you have a lot of attraction forces going only downwards and not providing any energy to move your system ;)If you orientate a magnet (stack) so north faces to the right and south to the left on either side of the cart you have more options.If the stack or single magnet has the correct length to match the angle of the magnet rows then a funny thing happens.Assume the outer most magnet is at about the same distance from center as the first magnet in the row.Means the inner most and opposing one is further away and the attraction forces gain the upper hand.While moving along though it moves away from the magnet row and whie still gaining force the last magnet in the row stops the cart dead center.This is the common scenario you see on the web when people try and fail.Now if you change the length of your working magnet and position in relation to the magnets in the row you can use the changes to your advantage.You can add slim disc magnets either side of your stack and observe the change in behaviour and where the cart starts to be repelled or gets stuck.In a bad case it starts fast but then stops with a big wobble back and forth.The perfect balance and size means the cart is attracted once it comes close to the magnet rows.There should only be a tiny sopt of very little repulsion right before the cart takes off.Like a hair trigger on a good gun if you know what I mean.It should then see some accelleration till about magnet 5-7 in a row of 14.From there it should level out and roll trough and keep rolling.I assume your first attempts now get you to the point where you cart start really nice, slows down a bit and seems just to miss a tiny extra push to make it out.It it shoots to the last magnet in the rows and then settles back to one or two before the end you are close!We have now two basic ways of manipulating the magnetic fields in our favour, or to "cheat" phsyics.Closing the gap.You will have realised by now that you need at least two stages for your system to be tested properly.Preferably 3 to get a 120° angle in a rotary conversion, but 5 would make sure there is hickups.This also means distance is now something to play with.Remember the pull before get at the same level with the first magnet in the rows?This is the first force we utilise by bringing the second stage at a distance CLOSE to take over the pull.Close because we don't want it to pull the cart out just like that.It would create a big "bump" and in a rotary system massive and unwanted vibrations.Instead we weaken the last magnet in either row.We still want to keep its pull but not so much the holding force that makes our cart go stuck here.Placing a magnet orientated in the same direction as your rows at the end of the row will change how and where the field of the last magnet in the row goes ;)Just to be precise: If the magnet in the row is north up and south down then the added magnet should have the poles 90° to that and in the same direction as the row.Depending how high, how close and with wich pole you place it the fields will change.You want to lower the locking force by at least 50% here - that will be suffient to overcome the holding force and gives the next stage a good chance to take over.It can also help to provide a sacrificial pole below the last magnet in the row.Again if north would be facing up then the lower magnet would also face north up but with a small distance to the upper manget.Ok, what happens here exactly?If I would want to be precise here you would need to read an awful lot, so make it simple...The lower magnet provides a way for the upper magnets south pole to get somewhere else instead of back to its original north pole.It also means there is another north pole "pushing" the north of the upper magnet more flat at the bottom half.This weakens the field strenght.Distance is key.The added magnet at the end does a similar thing.It provides attraction or repulsion forces that affect the field shape of the last magnet in the row.Imagine you have north facing towards the last magnet:You would push the last bit of the field up while also providing a very sharp end instead of a big round shape.The south pole of the last magnet also gets attracted by this added magnet, even more with one magnet below it.With those two added magnets you should be able to fully overcome the binding effect stopping your cart.It won't start and keep going when you let go of it half way down the track though, you need to start with the first magnet or give it a push to overcome the first binding effect.After that momentum takes over.If it really is that simple then where are all the successful videos about it?They are out there, you just need to look quite long for them.Most people still literally think only linear.A magnet has north and south and we can't change it - but we can...With field manipulations as above and shielding we get so much more than what physics currently dictates.Keep in mind that adding shielding under your rows of magnets will also affect how all works together ;)Some people forget this when using ferromagnetic things way too close to their testing area.Distance is also vital to keep in mind when experimenting.The closer two magnets are greater their forces to each other.You can utilise this for example by lowering magnets that seem to be far too strong in your configuration and cause a binding effect ;)And as said, shielding is nice thing for triack too - imagine what would happen with sielding on the sides of your magnet rows... ;)Make a negative into a positive!Extremly strong binding forces at a certain point in your track design can mean you might be able to utilise it instead of trying to waste it.Added magnets can divert the field to quite some extend.Shielding however can also direct them somewhere else - like in the core of a transformer where it all goes in a great circle.Even strips of shielding connecting magnets from one row to the one on the other side of the track can be utilised.Like that you turn two small magnets into one long one with twisted poles at the end.Provides more field strenght too and makes it good for areas with little to no attracting force to the cart.Then there is bigger design...Some people add a center magnet.With one on the cart and one in the center of the track you can create a cancellation field.The rows bind while the center magnet wants to push.If place where there is still enough forward momentum or even acceleration but close enough to the binding magnets it is possible to greatly lower the binding effect.But keep in mind you need to consider the added repulsion or compensated the field so it is most active towards the moving direction and less strong to where the cart is coming from.Advanced manipulations.You can machine magnets, sandpaper, file, grinder, CNC....Imagine you cut a square dice magnet from one corner to the other.Depending on how you have the field orientation you can end up several variations.But if north faced up in your dice then it will still face up in the cut pieces!Cut a pyramid and you end with a big flat south pole and a pointy north pole - and with extreme field strenth in this pointy bit.Similar story with half moon shapes.Imagine you machine a flat block magnet so you have a half moon with its pointy bits facing down and big round bit up.If north was up in the block and you shape the moon correctly then you end with two strong south pole points and a north pole that is strongest right between those points.Why is this so interesting you might wonder?Imagine you already know a magnets pole does not care if gos back to its own opposite or that of a different magnet.Then you also know you can machine and shape magnets to your will.Now imagine that for a change:Precisely machined pyramids that have the top chopped off.All tops in this example facing being the north poles and big bottom south.If you then machine a precise iron core block you make a nice cube.With magnets we need really good glue and a good press to make it happen.But if the center core is of proper size then we end with a block magnet that has a south pole on all sides.Of course to be 100% perfect we would need a zero tolerance gap but good glue and high forces can come quite close.Works as a sphere too but would even have clue where to start to machine the magnets LOL

Topic by Downunder35m  


Very old shielding materials and techniques for permanent magnets and resulting possibilities

Forromagnetic meterials are not just called that for no reason.It comes from ferrous - iron.Iron has the highest permeability at normal temperatures.That means a magnet is attracted to it very strongly.We utilise this for transformer cores, the stuff inside a relay and the moving latch of the relay itself.Like current from an electrical system magnetic fields like to take the easiest route possible.Air is a very bad medium, so any iron close by will be prefered even if it is at a slight distance.You can check with a magnet, a steel bar and some iron shavings - please cover the are with plate first ;)Slightly less known is the option to also guide and extend the magnetic field this way.If you check how far the magnetic field of a magnet reaches and note that distance,then you can add some steel bars or rods at the poles - the field will extend through the metal.The most powerful example of this are the shielded magnets used for hooks or speakers.Except for a tiny area the entire magnetic flux goes through the metal.So in this lefover area the magnetic flux density will my many times greater than what the magnet alone would be able to.What most people don't know is that magnets also interact with other magnets in terms of their fields changing and distorting.The Halbach Array is a good example of this.Seen as a single magnet the array would have one weak and one strong side instead of even strenght for both.Wherever magnetic fields change a conductor can produce electricity or current.This in return causes an electromagnetic field that opposes the one from the magnets.Just drop a magnet through a copper or aluminium pipe ;)Since these distortions are widely unknow to the hobby tinkerer mistakes can happen ;)In the early days of exploring science some people already knew about shielding.And they also knew that certain metals have certain properties.Where it is quite hard to create a good coil from steel wire, copper works fine as it is not magnetic.What would then a copper shielding do?If you have two moving magnets with only a tiny gap then the resulting field distortions are quite huge.A copper shield around the magnet like a pipe would then react to these changes and also create a megnetic field that works in relation to the enclosed magnet.In simple terms it means the shield would let the magnet appear weaker or stronger depending on the field change.A quite old document I found gave some hints on how people thought in different directions back then.It was in regards to the design of a magnet motor by the way.Here various magnets were shielded in tube made of a copper-bismuth-alumium alloy.These tubes were then electrically connected so it created a single loop conductor.The claim was that the resulting electromagnetic field of this ring would drive the fields of the enclosed magnets sideways out of alignment.Like bending straight pastic tubes sideways.This "pulsating" would always happen when the magnetic binding forces reach max and so basically drastically weaken this binding effect.Another document talks about a "magnetised brass rod".A holes of the rod diameter is drilled through a block magnet.Not from north to south but through the middle where the flux is greatest.The claim here was that if that rod rotates fast enough a very low voltage with a very high current will be generated.Sounds easy and interesting enough that I might have to test one myself one day.The best one however is what I consider a hoax or being as good as Starlite.Someone back in 1908 claimed to have created a material the reflects magnetic fields.In lame man's terms it would be like an insulator around some electrical wire.The claim and some pics showed it, was that no magnetic field can pass the material.Or to be correct only a tiny fraction of what would be possible through air.A small magnet inside a longer tube of this material would create almost the same attraction to steel at the tubes ends as on the magnet itself.Measurements showed the field strength would be almost equal to a long mangnet of the same field strength.Imagine guiding the field of a big and powerful magnet through a tube around some corners or other magnets and then end in just a tiny hole for the entire flux...Too bad he never shared his secret formula to anyone knows to mankind.Isolation...Imagine you have an array of changing magnetic fields and quite strong magnets.Then you might face the problem that your focus on the "working" end neglected the other end of the magnet (stack).Providing some iron core material will keep thes field lines contained and away from interfering with your setup ;)But it also allows to use te otherwise unused end of your magnets more directly.For example by guiding to another magnet to affect its field strenght ;)Placing a sheet or steel between two magnets in a setup provides a "shared pole" so to say.If you have a north and south pole on a rotor at a distance of 5mm then a sheet of steel between will drastically weaken the strenght and reach of this combined field.It is like pulling the arch between the magnets down to make it more flat.And at and an angle the resulting field will also be slightly angled ;)Capping...When I first encounter this many years ago I couldn't really make sense of it.Quite complex..If you check the magnetic field lines with iron filings or similar then you notice how they go in a rounded manner from pole to pole.This is because the single field lines are of equal polarity and will dirve apart like opposing magnets.By capping the ends of a magnet you provide a short.Instead of diverting out like mad they will follow the cap and create very intersting magnetic field in return.If both poles are capped it is like pressing the magnet flat but without having a field on top of the oles - only aorund the center part.For this the thickness much must match what is required for the flux density.As a rule of thumb: if the end is still very magnetic then it is not enough material tickness ;)Interacting fields in a tube...This one is quite old too and seemed to have found no usable inventions apart from simple magnetic spring replacement systems.But it gave me some clues about Tesla "earthquake machine" ;)If you place a magnet in a tube and at it's ends magnets with opposing fields to the one inside then you can fix this magnet in place.Push one magnet deeper and the distance from the inner magnet to the other end will shrink the same amount.In this old paper two coils were around the pipe with the inner magnet between them.In this gap and at about the same width as the magnets length another coil was placed.Violent shaking would then create electrical energy at much higher level then modern shaker torches.In return an AC current on the outer coils would cause the inner magnet to move back and forth to create electricity in the center coil.According to the paper possible uses include: core less transformer, measuring minute changes in AC voltages, providing free power from a running motor...The last one had me stumbled for a very long time.Until I considered a different configuration.The whole thing is basically a linear DC motor - with correct timing of course.And in some motors we use permanent magnets.I am starting to wonder what would happen if we would design a rotor magnet like this?The running motor would be subject to constant field changes that affect the rotor.And a normal motor is always "even".By using four magnets instead of one we can push the field really flat.This means the area where the coil would operate (about 1/5 of the magnets area) will have a much stronger field.The resulting torque should be higher by about 25% !!Even a simple two coil model setup should show a significant increase in performance here.Timing is critical here but I tried some calculations based on 8 poles and the required "on times" for the coils.In a standard motor configuration with a single rotor magnet the coil is active for about 12° of the rotation.With a 4 magnet configuration this "on time" can be reduced to under 8° of the rotation to get the same amount of torque.An energy reduction of about 4% if you neglect losses and only think in time.If you think in terms like impulse energy then we are talking of about 15% !Shorter on time but still much higher flux density overall than for the long standard timings.Going the long run now:If you check how most DC motors work then you realise soon that for most one rule seems to followed.Only use one coild pair at a time.This is quite contradictive if you consider the geometry and options.A dual commutator would allow to use a second coil pair with a field OPPOSING the magnets instead of being attracted to it.After all: on you bike you pedal with both legs and not just one...And if you do it professionally then yu do the same as I suggested for the motor - you use the up pull of your legs as well.Doing it brushless only requires amodified h-bridge desing to drive the second coil pair at the right timing.Some will now say that it requires twice the energy, I say that for the same motor size your get twice the torque!Just imagine what that means in possible weight reduction for a motor - or its size to deliver the same torque at the same power levels when a normal motor is used ;)The more poles the more complicate the precise timing but no big deal really with modern electronics.Can it be improved even further?I though long and hard about that one until I considered EMF.A DC motor produces a lot of it when the elecromagnetic field collapses in the the coils.We do not utilise this energy...There is a tiny delay until the released energy levels are at max.My theory is that it should be possible to divert this energy into another coil set.If that coil is not the next active but still within a strong enough field area then the EMF would actually add to the drive of the motor.Only downside is that according to my calculations at least 16 poles would be required to get an optimum result.Way above of what I can create in my little garage :(In theory it should then be possible to reach about 98% efficiency for the motor....

Topic by Downunder35m    |  last reply


Magnets, Magnetism, Field lines ???? An expert is needed for green wind power.

This is best placed in the green group as it is for the production of green electricity, but I think that it would not be out of place in the science section also. I have an idea, quite probably not an original one but an idea all the same. It came about as we go camping as a family and have been off the grid a few times. Basically we have had no way of charging our electronic devices for longish periods. Solar power I hear you cry, well that is all well and good if you live in a country that has good sunlight, but here in the UK it can be unpredictable and not produce enough charge to power modern devices. I am mucking about with dynamo’s on the bikes (pedal ones) and wind up devices. Something I am looking into is things like wind power or improved dynamo power. The basic principal behind all of these forms of power production is that of passing a conductor through a magnetic field to produce a potential difference on that conductor. Simples (reference to meerkat advert http://www.youtube.com/watch?v=NBu0OtC6m9g). It has been a very long time since I have done anything like this (way back in school all those years ago) so please stick with me on this one. If I remember right the principal theory is that 1. The higher number of conductors (or loops in the coil) that passes through the field lines causes the voltage to be higher. 2. The stronger the magnetic flux the higher the current production within the conductors. This is a bit basic to some of you I am sure but I still need to get it out to confirm my thoughts. If this is wrong please correct me, as the title says, an expert is needed lol The bar magnet field lines project from the N end and loop back to the S end in this fashion Image 1 Putting two bar magnets together with N and S facing gives a field pattern like this Image 2 Now this is where I need the most help with. Toroidal magnets produce a different field pattern, and as far as I can make out from the internet it looks like this Image 3 & 4 What I want to know is what happens when you put two toroidal magnets on top of each other, what happens to the field lines then. I have thought that there are a few possibilities on this, the first is that the circular lines will extend to encompass both magnets creating like an hour glass formation in the cross section. The second is that field lines will combine/intermingle between the magnets and create a figure 8 pattern. In either of the two possibilities the field strength will be increased to what could be considered a focal point between the two magnets. So with the technical thoughts out of the way and progressing on the assumption that I am correct so far my thought of a high powered dynamo is this. A central shaft that is spun by wind or other means, attached to this shaft are disks like platters on a hard drive, attached to those platters are the toroidal magnets. The magnets are aligned and spaced to give maximum condensing of the field lines between the upper and lower platter. In the centre of the two (or more) platters is a fixed platter, not attached to the shaft and is stationary. On this stationary platter are the coils, fixed into position. Image 5 The coils are shaped and could be something like the voice coils out of a hard drive, which would be good as they would determine the size of the platters, being key stone shaped they will fit together to make a ring of coils. Image 6 The whole idea is based upon the maximising and focusing of the field lines from the magnets to a point producing the maximum amount of energy as the coils pass through the lines. I also think that due to the shaft being turned having little resistance or weight that even small amounts of wind energy would be able to turn it to produce the desired outcome. Now this is where I ask you all to comment and take my thoughts to bits where I have assumed things that are wrong. I have no problems being told where I am wrong as long as it is not in a nasty way. Cheers all

Topic by Batdragon  


Questions about Magnets

Can an electro magnet have more gauss than a neodymium of the same size?  I was just thinking about robots and advanced prosthetics. One issue with them is they require rather bulky motors to get the lifting and holding capacity we often require. So if power wasn't an issue and you could make a small elecro magnet that has more gauss/a stronger magnetic field than a neodymium magnet. Than we could make strong and smaller motors.  Just a thought. Discuss!

Topic by mpilchfamily    |  last reply


how far can an electromagnetic field reach?

For my project I need to know how far electromagnetic fields can reach. I am guessing its related to power and materials, but perhaps there is some kind of rough formula for calculating potential reach? By reach, I mean, how far can the magnetic field reach and attract (move) something, like metal fillings. Also, is there anyway to know how quickly a magnetic field can move something. In other words what speed will metal fillings move at when the electromagnet is switched on? Thanks all, Joel (the snow athlete)

Topic by snow athlete    |  last reply



About the components of light ?

I just learnt that light consists of electric and magnetic fields oscillating at right angles to each other . Now my question is that why can't the electric and magnetic components of light interact with matter. For example why does not the magnetic component in light interact with a external magnetic field and bend toward or away from it. Also how do we tell the direction of magnetic and electric fields in light . I know that this question might seem really dumb , but i seem to have a great difficulty in understanding light and would be really satisfied if some could give or direct me to a detailed explanation. Thanks in advance ..

Question by Strontium    |  last reply


Does an inductor start with a magnetic field, or does it only retain one as long as it is powered?

I am trying to figure out how to keep a reed switch on by proximity to a magnet. I read that an inductor stores the current as a magnetic force, so I was planning on just having the reed switch close to the inductor, and just use a small magnet to close the circuit initially. i was hoping the field from the powered inductor would keep the switch closed. Am I on the right track?

Question by redbaron1234    |  last reply


How to measure electromagnet by Tesla?

I will be doing an experiment how powerful the magnetic field of an electromagnet, and my guess is the more you twist the wire the more power it generate. But i don't know how to measure the magnetic field by using the unit Tesla.

Question by defineSCIENCE    |  last reply


A way to calculate something about a ferromagnetic ball in a magnetic field? Answered

I've built something like this https://www.instructables.com/id/Mechanical-Rail-Accelerator---Non-electromagnet-%22r/ and now I am thinking of calculating the kinetic energy of a ball flying off the magnet if it was 'set off' by a ball at some velocity. I have a great lot of problems: 1 The ball is about the same size as the magnet, which makes it impossible to say it is 'infinitely small'. 2 It is near the pole, so the magnetic field is not even (not like inside a coil). 3 The ball is ferromagnetic, so the field is going to be even more disrupted. 4 There is no Physics teacher this week. Maybe (I hope) there is a formula of potential energy of something like my ball in a magnetic field? Any ideas? 

Question by gruffalo child    |  last reply



how can I magnetic distance?

So for the past month my study has been magnets (how do they work) and ive come to electromagnets. what variable/s would affect the distance of a magnetic field. or rather what produces a bigger field, higher voltage, or amperage? thin wire and many wrappings or thicker wire and fewer wrappings. also if anyone knows of any good simulations on electromagnetism they would be much appreciated  

Question by snowfox222    |  last reply


what is tesla turbine???

Is it related with magnetic field?

Question by kbisht    |  last reply


Magnetic Levitation Tram? Answered

Hello there instuctables, I need your help with a project i am attempting, i am in the process of making a maglev tram and i have a couple questions i need help with? 1. I have a simple circuit for a linear motor that i understand to the most part but i need help with finding an electromagnet to use / make, it needs to run on batteries and obviously the main concern here is weight and stability so the smaller the better but still needs to be strong enough to propel the tram along the track so i suppose my real question is what ammount of winding, resistance and core material would be suitable for whatever voltage i could provide! 2. Next i suppose what way round should i place the magnets, should i place many electromagnets on the rail with sensorsand permanent magnets on the tram, or should i have a powered electromagnet on the tram and permanent magnets on the track? 3. Also what hall sensor should i use to detect the magnetic fields, unipolar switches or ratiometric sensors? 4. And finally control, how would i control the motion of the tram i.e. speed and direction? Id like to thank you all in advance for any help you could provide and i hope my description is accurate enough!! many regards, Scott Photo of simple linear motor circuit (img.1) When the hall sensor (switch) senses a pole of a magnet, it activates the transistor, in turn magnetising the relay and causing the current in the electromagnet (motor) to run one direction, then as the opposite pole is detected the relay de-magnetises and reverses the current thus reversing the pole on the electromagnet! This is designed so that with permanent magnets on the track in an alternating fashion of poles (nsnsns) the tram is either pushed or pulled along the track! 

Question by Xmortx114145    |  last reply


Slow-discharge circuit for gradually diminishing electromagnet field?

As I understand electromagnets, you wrap a wire coil around an iron rod and run current through the coil. As long as there's current going through the coil, you have a magnet... But when you cut the current, no more magnetism... I want to create a circuit in which a hand crank charges up one or more batteries or capacitors, which in turn discharge slowly through an electromagnetic coil (such that the magnetic field of the electromagnet gradually diminishes) over the course of an hour or so. The overall idea is that you crank the crank for a short while, creating a magnetic field so that BBs cling to the electromagnet. But little by little, over the course of maybe 20 or 30 minutes (longer would be OK), the BBs drop off one by one (or a few at a time). Can anyone suggest what such a circuit might look like? What variables will determine how long the crank has to be turned, how strong the magnetic field will be and how slowly it will discharge? And will the BBs only cling to the ends of the electromagnet? Or will they cling along the length of it as well? 

Topic by Donny Bahama    |  last reply


Magnetic stirrer and springs....

Wanted to try how far the magnetic field of my new stirrer is reaching and observes something weird...If you have a normal stirring rod in a beaker then these things do excatly what they are supposed to.Even if you try to add the rodd to an empty beaker while the stirrer is already running.The first option gives you a nice rotation, the later often just some jumping and bouncing rod.Fun fact though: Inside a stirrer rotates a magnet and the rod is just a steel bar enclosed in polyethylen or teflon.Trying to make a stirring rod roll around the center instead of rotating is next to impossible - it always tries to use the max binding force and centers itself.So I tried different things for the end goal of designing a stand up stirring twoer instead.You know, like these fancy ones found in huge water towers to agitate the water.I found a small steel ball with two magnets attached quite interesting but an accident made me wonder...For some reason I did not turn the stirrer fully off when searching my little box of goodies for new stuff to try.A small spring for some motor bushes landed on the stirrer...And although it moved dead center it did not spin at all.A slight vibration was all I could see.First weird behaviur happen when I tried to move the spring around to check why it is not spinning.Pushing it a bit lengthwise suddenly made it spin!A bit of fiddling a trying showed it works best slightly off center to the magnet with one end while sitting on the radius.The spring rotated like a horizontal drill but in no relation to the stirring speed.Second and even weirder things happened when the spring slipped through my fingers.It started to roll around the center of the plate but in the opposite direction to the magnets rotattion!An increase in speed made it roll faster until the g forces made it fly off the plate.If you have a magnetic stirrer then try it out one day.I have a few theories why the spring starts to rotate or roll but none make fully sense.Can try to take a video for those with no stirrer but for the fun of it it might be good to just mount a magnet on a motor and try LOL

Topic by Downunder35m  


Why is my electro magnet switching on and off?

I've recently built an electromagnet with a DC power supply off 5v 4a but when I turn it on it goes on and off . I'v checked this by downloading a sensor on my phone and surely enough every second the magnetic field goes higher than my phone's range and then returns to normal can you please explain why and how to keep a constant field

Question by charlie30122004  


Why is my electro magnet switching on and off!

I've recently built an electromagnet with a DC power supply off 5v 4a but when I turn it on it goes on and off . I'v checked this by downloading a sensor on my phone and surely enough every second the magnetic field goes higher than my phone's range and then returns to normal can you please explain why and how to keep a constant field

Question by charlie30122004    |  last reply


Help!! LED Candles- Magnetic Switch

Hi,I am working on a Play and we need candles. Since we can't have open flames on stage (fire code=lame) So I want to build or purchase some LEDs candles to use. Here's the catch- I want the actresses to be able to "light" the candles. So my idea was to put a rare earth magnetic in a match book and have them hold it near the candle to start up the LED. The only problem is that with all of the magnetic switches I have seen they are momentary. I want to be able to remove the magnetic field and still have the light be on but once I put it back towards the candle I want to turn the candle back off. Any suggestions of a switch like this or any other bright (no pun intended) ideas?ThanksAll comments/ questions/ concerns are welcomed.Thanks again.Joe

Topic by joejoerowley    |  last reply


Is it possible to transfer data via magnetic induction between two coils separated by a steel plate ?

Is it possible to transfer data via magnetic induction between two coils separated by a thin steel plate of 2mm ? Or does the magnetic field gets diminished by the metal plate?

Topic by ZZamorin    |  last reply


Electromagnet using permanent magnets

Hi All, I'm attempting to make a very small strong electromagnet using permanent rare earth magnets. I want to boost the magnetic field and increase the magnetic force. The magnets are 10mm in length by 5mm in radius. I have 0.4mm2 enamelled solenoid wire for the winding. My questions are, Is it possible to increase the force of a permenent  magnet? Will the induced flux into the magnet compile the force or will the EMF have to be greater to see an effect? Will paralleling two windings make the EMF stronger? As the magnets are small I have limited room to wrap windings so is there a more effective method? Any help would be great!

Topic by JimmyM5    |  last reply


Why aren't coil guns made this way?

In a physics demo, my teacher used a small coilgun,  but it used low voltage AC, not a single high voltage burst, also it used an aluminum ring on the outside of the coil instead of a slug on inside of it. Apparently the AC creates a changing magnetic field, which induces current in the ring giving it a magnetic field as well...

Question by falzarbeta    |  last reply


Making a magnetically suspended puppet. Answered

Hi, I'm thinking of making a magnetically suspended puppet. The idea is to make a puppet with a neodymium magnet in its head, and suspend it under an electromagnet, using a microcontroller to control the (DC) suspension current. To regulate the current, I'll probably use a D/A converter chip controlling an op-amp current sink, though I might use low-pass filtered PWM D/A conversion. I was thinking of a way of sensing the vertical height where I put a small chunk of metal in the head as well as the magnet, modulate the suspension field slightly at a high frequency (20 kHz?), and have an extra sense coil around the suspension coil. The idea is there would be an induced current in the sense coil from the modulation. This would change as the metal chunk came nearer to the centre of the coil. The signal from the sense coil would go through a high-pass-filter (to remove any low frequency components like mains), an op-amp rectifier, and then a low-pass filter, to produce a sense voltage. I might try both para- and dia- magnetic metals (iron and aluminium) to see which works better. I'm not entirely sure whether this will work, but I'd like to try it as it seems more elegant than using a hall effect sensor. The questions I have are: - How would I go about calculating roughly what length of wire and current I'm likely to need to suspend a given weight? Just a pointer to the relevant maths should be OK - don't feel like you to have to spell it out. - Does it make any difference whether the electromagnet is long or short along its central axis? I had an idea that the field from a longer coil might extend further below the magnet than one from a shorter one, but I don't know if this is so. - Does the method I've described for sensing the height sound practical? Thanks for any help, andy (ganglion)

Question by ganglion    |  last reply


Coilgun or Railgun? Answered

               I want to build either a coilgun or a railgun, using a bank of camera capacitors as the power source.  Experimenting with small coilguns, I've found that the efficiency is very lacking.  I haven't done the math, but five camera capacitors in parallel with a medium-sized coil will barely move a half-inch screw.  So which should I go for for better use of available capacitors--coilgun or railgun? P.S.  I've found places on the internet that give tutorials on making capacitors, which I would also consider doing.  If I'm able to make large-capacity capacitors myself and use those, should I build something other than what I should make if I only have access to camera flash capacitors? P.P.S.  I heard the following rule somewhere here on this site:  "The more amps in a coil, the more powerful its magnetic field, the more voltage in a coil, the larger the magnetic field."  Is this true?

Question by mad magoo    |  last reply


Is there a way to reduce a magnetic fields power in a certain direction, while on a tight budget?

I'm going to make a coilgun with roughly 9 flash camera capacitors of varying values. Due to how I have limited resources, I intend to make this coilgun as efficient as possible. I want to know if there is a relatively cheap way to prevent the magnetic field from the coil from reaching to far in one direction, or severely weaken it's power in said direction. I don't know if I saw this somewhere or thought of it, but if the coil has less drag on the projectile once it passes it, it should put into effect a fair boost on the efficiency. Another idea, no idea if it was originally mine or not, is to slot the barrel of the coilgun reducing to force needed to push the air out, and overall reducing friction & drag. Would this have a noticeable effect, do you think?

Question by StartedBullet    |  last reply