Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnetic induction question.

  1. Jul 21, 2011 #1
    new guy here with a simple magnetic theory question.

    if i were to coil 10 turns of insulated wire around an 1/8" round x 1" long neodymium magnet, then wire it in parallel to a second magnet with 20 turns of the same gauge wire, what kind of change could i exspect in the second magnets field if i spun a reluctor in front of the first magnet?

    im trying to boost or weaken one magnet with another......remotely, without any type of outside power source. only induction slightly amplified by verying the number of coils between the two magnets.

    to clarify my question and give you a reasonable motive behind my questions, i drew up a picture.

    my question is when the reluctor wheel passes past one of one magnet what kind of response will i get in the other magnet?

    -will there be an increase or decrease in the other magnets strength depending on the direction of the windings in the coils?

    -will there be an equal response from each magnet across the grid as a metal object passes by it? "depending on the accuracy of each coil of course."

    -could a magnetic image somehow be broadcasted from one grid to the other through the use of mercury or metal filings on one grid and a metal object passing over the other?

    these are just a couple of the questions i want answers to. in order to build a grid i need time and money. just want to know if ano of the answers are already out there before i waste both.

    i already know that a small amount of voltage will be induced in the coil of the first magnet. but is that voltage enough to change the magnetic properties of the other magnet?

    Attached Files:

    Last edited: Jul 21, 2011
  2. jcsd
  3. Jul 21, 2011 #2
    I don't quite understand how you are trying to induce a voltage in the first coil...what's that that you call reluctor? Your device does not look anything like the most basic generator...you need to re-visit that.

    Also, your two coils are actually in series, not in parallel...while this may get ambiguous when you are talking about just 2 devices, the condition of "in series" means that the same current is flowing throw the devices..as it is in this case.

    Anyway, it does not look to me that you are going to get anything out of this device.

    ...and what is that about a grid? I don't follow.
  4. Jul 22, 2011 #3
    in the picture there are actually two devices.

    ill break each one down a little further.

    the smaller one is a generic view of a wheel speed sensor found on a vehicle.

    I'm an automotive technician so please excuse the terms i use. a reluctor wheel or tone wheel is the object connected to the axle shaft behind the tire and it spins in relation to the tire.

    the permanent magnet that is closest to it would be considered the wheel speed "sensor". on the vehicle it is mounted stationary on the suspension. as the tone wheel rotates, the fins pass through the magnetic field. as each fin exits the magnetic field it induces a small amount of voltage in the coil. so i kind of referred to it as the generator in my brain...

    the second magnet and coil would be used as an electro magnet, although it is in fact a permanent magnet.

    in theory the voltage induced in the first magnet would be transfered to the second magnets coil. this would manipulate the magnetic field of that magnet for just a split second causing it to either weaken or get stronger.

    this would " in theory" allow something placed on the verge of being pulled toward it to either be pulled toward it or let completely free.

    the larger of the two devices is a grid of these individually wired 1:1 and then placed in sequence. this means that the top left hand magnet on the left grid is wired to the top left hand magnet on the right grid. they would all be wired in reference to where they are at on each grid.

    if my first theory is correct, and a magnets field can be manipulated and broadcasted to a second magnet over a twisted pair, the grid device could be used to magnetically broadcast from one grid to the other.

    if laid down flat on a table this grid could possibly be used for some interesting experiments. a sheet of glass could be laid over it and either metal filings or mercury could be placed over one grid, and the second grid could be used to manipulate the shape or movement of the medium by moving a metal object over top of it. it may not be an equal reaction, but any reaction would be a start to something new.

    if one permanent magnet can be manipulated remotely by another, "without ANY source of battery power" other than magnetic induction itself, it can be a usable function.

    the strength of the 3" dia x 2" long Neodymium magnets i messed with back in college was amazing. we towed a h2 with them clamped to two separate ropes and then stuck together without them ever coming apart. that is impressive!

    if there was some sort of way to control just a fraction of the magnets abilities simply with magnetic induction and no other outside power source, the magnets could be used to do work without using any outside resource.

    clamp one magnet to the edge of a table with a plastic clamp and place a second magnet on the table in front of it poles N to S "just on the verge of being pulled toward it". then pass a metal object in front of the side hanging over the edge of the table and watch what the loose magnet does. in short this causes a pulse of strength in the magnet being induced when the field snaps back.
    Last edited: Jul 22, 2011
  5. Jul 22, 2011 #4
    I kind of get it, but not quite.

    In any case, my comment still stands...you configuration at the wheel does not look like a generator...

    ...if you had a permanent magnet at every fin in your reluctor and actually remove the magnet from within that one primary coil, you would be in much better shape...

    I am not sure how close things are or you want them to be, but the initial thought is that those magnets on the fins of the reluctor should alternate in polarity, this would require you to have an even number of fins in your reluctor...

    or, if you are not looking for much generation, you can leave them all in the same polarity (allowing for a reluctor of even or odd number of fins) and kind of use the space in between them to 'produce' the change in field.
  6. Jul 22, 2011 #5
    thank you for challenging my idea. that is actually what i was looking for by posting my questions on this forum.

    i do see your point. i understand that a magnetic pulse generator uses a coil wrapped around an iron core, and a small magnet attached to the non induced end to generate a pulse as a ferrous material is passed by the iron core.

    in my mind the larger iron core just makes them cheaper to build. also, the voltage generated by them is small, and they are usually only used as sensing devices.

    i need a stronger pulse from mine in order to effect the other magnet. if iron "needs" to be incorporated in order to generate a pulse, i only want to use enough iron to accomplish it. but due to the fact that the neodymium magnet is made in part with iron, i see no need in adding more.

    here you can see one of my project ideas. there is more to this project that you cant see, and i wont be posting it up any time soon :wink:

    in this picture the reluctor would be spinning and creating 12 pulses at the same time and alternating between 2 sets of magnets 24 in all. each magnets pulse could be used individually or together in two groups of 12.

    so, if some how i was able to get one volt from each coil, wiring each group of 12 in series would add up to 12 volts. but I'm not expecting 12 volts to come from this.


    here the reluctors are doubled up and move together. this induces both ends of the magnets. in theory the magnetic field will be stretched out in both directions and then once the reluctor tooth passed it would collapse into itself in both directions. what it would produce is unknown to me.


    what if the same poles were held at close proximity to each other and a shield was passed between them? would the magnetic fields still be attracted to the reluctor, and once it passed by, would the poles repel each others fields causing a stronger collapse resulting in higher inductance readings?
  7. Jul 22, 2011 #6
    sorry for errors in my terminology. if i understood half of what some of you guys talk about on here, i probably wouldnt need to be a mechanic for a living. i would love to be able to work out some of the mathematical equations ive seen on here and grasp some understanding of what youre talking about. it would sure help me with all of the questions i have no way of putting words to. theorys more or less just kind of stand out in my mind without much mathematical knowledge to back them up. im more the fly by the seat of my pants kind of guy. i think ive been electricuted one too many times...:confused:
  8. Jul 23, 2011 #7
    I will say it again...take the magnets out if the coils!...they are actually working against you!

    Put the magnets in the reluctor fins, put iron cores in the coils.

    In fact, you could benefit from the 'outside' reluctor but it does not need to be spinning and you would benefit from core in between the coils, too....this is call the 'stator'...

    Just go an open an electric motor and you will see what I am talking about...you will see coils wound around laminated core.

    Also, you should probably visit some http://www.allaboutcircuits.com/vol_2/chpt_1/1.html" [Broken] page and read some.

    You don't have to experiment and re-invent the generator, you know, they have been around for quite some time.
    Last edited by a moderator: May 5, 2017
  9. Jul 23, 2011 #8
    after my post last night i was doing research on what you told me and saw the flaw you pointed out to me. thank you. i had a back to text book moment. i can still add iron to my plans. it only changes a few things. but in multiple ways this made my project even more accoplishable not only by the simple fact that my first idea wouldnt have worked. this also gives me a simple reluctor wheel. but this still doesnt change the fact that i need a way to minipulate a second magnet in order to do what i have planned. and im not exactly trying to build a generator. as i said before i have the rest of my plans hidden in the sketchup pictures i posted up. and that part is finished. i need this part in order for the other to work. this is so far the only snag in my plans.

    the minipulation of the second magnet only has to be small enough to weaken it just for a split second in a single pulse. if it was to weaken it just enough allow another unminipulated magnet connected to the same wheel to over come its strength, at that moment the unminipulated magnet could take its place. this would result in movement of the wheel which in turn could generate a second pulse and so, on. the end all answer i need to find is:

    can the pulse generated by one magnet minipulate another magnets strength without causing damage?
    Last edited by a moderator: May 5, 2017
  10. Jul 23, 2011 #9
    I don't have practical experience dealing with magnets, but you don't have to worry about damage, that's for sure.

    A weak coil will not do much to a magnet, but it will add or substract its own magnetic field to it...which seems to be what you want.

    Just go ahead and experiment to your heart's content and answer your question for yourself.
  11. Jul 23, 2011 #10
    thanks man. thats all i needed to know.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook