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Dust aluminium atracted to magnet

  1. Nov 4, 2011 #1
    Hi

    Sorry I'm not good in physics at all.

    I have the following dust problem becoming attached to Nickel coatings.
    from what i know Nickel can become magnetic
    but aluminium should not be attracted to magnets.

    I did an experiment to confirm if the nickel coat is acting as magnet
    in which i used a regular clean magnet and aluminium foil and a very sharp knife.

    Cut small pieces of aluminium foil (less that hair thickness) with out touching them
    I clean the magnet with alcohol and let it dry.
    the i passed the magnet near the aluminium particles or touch them.
    if aluminium foil particles are small enough you can pick them with the magnet.

    the smaller particles are attached faster and
    you can even see the pull of the magnet when its getting near.

    I tryed also to pick the same particles with the knife, and they just dont get attached to the knife.


    DOES ANY ONE HAS AN EXPLANATION WHY ALUMINIUM PARTICLES GET ATTACHED TO THE MAGNET?
     
  2. jcsd
  3. Nov 4, 2011 #2

    Bobbywhy

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    Looser74, Welcome to Physics Forums! You can become a competent observer of nature by using the scientific method. You already seem to have a good handle on the method. You may want Google it and learn it thouroghly...it always serves the observer and experimenter well.

    As for your experiment: we know aluminum is non-magnetic, so why were those little aluminum particles attracted? You have misinterpred the results of your experiment. It is not magnetic attraction you are seeing. Answer: Unlike static electrical charges attract. So one object, say the aluminum, has a small positive static charge and the magnet has a negative static charge. You could probably get the same results using your rubber comb. Try experimenting with other materials. Google static electricity. Wikipedia and Google are your friends.
     
  4. Nov 4, 2011 #3
    In fact only one of them would have to have a small net charge which would polarize the other object and still cause attraction.
     
  5. Nov 7, 2011 #4
    If this was electric static wouldn't the aluminium foil be released as soon as it touches the magnet?
    to attrack objects by electric static they need to have oposite charge, once they touch both materials are conductive, and should neutralize the charge, but they stay attached
    even if waved strongly.
    until i remove with my hand or other object to pull the aluminium away, they stay attached.
    the attraction is not that strong but strong enough for the aluminium particle not to be released by gravity.
     
    Last edited: Nov 7, 2011
  6. Nov 7, 2011 #5
    static electricity...one they touch they should neutralize? Not so fast.

    Growing up in México, I remember having parties where the girls/women would come in, inflate balloons, rub them against their hair and place them along the top of the walls of the room...such balloons would stay there for the duration of the party or even longer.
     
  7. Nov 7, 2011 #6
    Well, balloons are not conductive, actually not even dissipative, charge doesn't go anywhere in balloons, unless you increase the air moisture.
     
  8. Nov 8, 2011 #7
    wait, who has a point here, you or me?

    I mean, if balloons are not conductive...how did the charge got in there in the first place? I had a balloon in my hand, push it against the wall and it does not stick...rub it against my hair, push it against the wall and it sticks.

    By the way, you said
    are you sure that your magnet is conductive? I think this is one big assumption on your part...I think most popular magnets are made out of some non-conductive ceramic material.
     
  9. Nov 8, 2011 #8

    phinds

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    He is correct about the conductivity and his point is valid. It is NOT necessary for objects to be conductive in order to get a STATIC charge. Is your hair conductive? Rub a balloon against it and see what happens.
     
  10. Nov 8, 2011 #9

    DrDu

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    It is not true that aluminium is non-magnetic. It is not ferromagnetic but is quite strongly paramagnetic. This could be sufficient to explain sticking to a magnet.
     
  11. Nov 8, 2011 #10
    Paramagnetic materials generate currents when a magnet moves near it, but would this be enough for the aluminium to hold to the magnet if its small enough?
     
  12. Nov 9, 2011 #11
    I just cut a strip of foil, 3 cm by 15 cm, and used a rare earth magnet to see if there was any attraction. There was. I think there might be a percent or so of iron in the aluminum, perhaps to make it a little more rigid.
     
  13. Nov 9, 2011 #12
    That might be true, Iron would make magnetic, i wonder how much content of Iron the Aluminium foil has?.

    how did you make the test?
    You need to have both magnet and aluminium foil still.
    otherwise you will generate eddy currents,
    that will make the aluminium foil temporarily magnetic and make it follow the magnet
    and it will look like the magnet is pulling it, but doesn't stick to the magnet.
    its just the eddy currents.
     
  14. Nov 9, 2011 #13

    NascentOxygen

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    Almost certainly that is the explanation. Liquid oxygen, too, is paramagnetic, and is attracted to a magnet. http://www.youtube.com/watch?v=yJs5ENtilIo"

    Though, we haven't discounted the possibility that attraction is due a magnetic impurity in the Al metal. OP should cut foil into a pencil-length strip, and repeatedly stroke with his magnet to attempt to magnetise the metal strip. If foil is too weak to support itself, float it on a plate of water and determine whether one end is repelled, and the other attracted, by the approach of the magnet. This won't necessarily prove iron is present.
     
    Last edited by a moderator: Apr 26, 2017
  15. Nov 10, 2011 #14
    I cut a strip of aluminum foil about an inch and a quarter wide by about 6 inches long. I dangled the long end down, in front of a rare earth magnet on the refrigerator door. The foil deflected slightly when it got near the magnet, finally getting pulled to the magnet. The foil deflected even more when I pulled it away from the magnet.

    The magnet was "still" insofar as it was on the door of the refrigerator. As for the strip of foil, I moved the bottom of the strip slowly toward the magnet till it began to deflect toward the magnet. The deflection was unambiguos.
     
    Last edited by a moderator: Dec 4, 2011
  16. Nov 10, 2011 #15

    Low-Q

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    It might be small amount of magnetic material on the aluminium, or static charge ofcourse. Btw., have you tried to approach a strong neodym magnet close to tapping water? If you poor water carefully, in a narrow flow, the water will deflect away from the magnet. How cool is that? :-))

    Vidar
     
  17. Nov 10, 2011 #16
    Vidar,

    I just tried that. Amazing. It pushed the stream of water away.

    I saw, on the KJMagnetics site, a magnet depressing the surface of still water. The deflection was made evident by looking at a slant angle of a reflected pattern on the water.
     
    Last edited by a moderator: Dec 4, 2011
  18. Nov 12, 2011 #17

    DrDu

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    One more point: The force between two dipoles goes diminishes like 1/r⁶. Especially the corners of a magnet were the field is very inhomogeneous may correspond to a strong dipole of very small radius. So the attraction on a small particle in which a dipole moment is induced can be very large despite the relative small value of the permeability.
     
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