Lenz's Law Demonstration - Magnetic Physicists Needed?
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The difference is that the pipe allows for complete current loops around the circumference of the pipe, which will generate a magnetic field in opposition to the falling magnet.  In a coil, with the ends disconnected, you won't have this happening.  You induce some emf in the coil, but it's not a closed circuit, or at least not one that can generate a magnetic field opposing the falling magnet.  You could consider small current loops induced within the wire, or around the circumference of the wire, depending on the magnet's orientation, but these will be small and weak compared to a current loop all the way around a pipe.  However, if you wire one end of the coil to the other,  you should get some Lenz's law braking of the magnet.   \n\nIt's a very clever idea for a demonstration.  I had to go set it up and test it myself with some magnet wire wound around a glass tube and a glass tube sheathed in a copper pipe, to see the effect you described.  Like I said, if you connect the coil to itself, you will see some effect, but it's not nearly as strong as the copper tube.  I think this is because the emf is induced in the coil as a whole, and not as a local loop as in the pipe, so you have a field of the same total strength, but it's not as strong locally. I think I'm going to have to play around with this some more and maybe do some actual math to figure out the full details.
537198
See the listing of suppliers given in the source below.  If you want to do magnetic separation, you'll want multi-domain particles, which means using particles *larger* than about 100 nm (depending on the material).
49236
ok, well, let's start with a basic description of magnetic materials.\n\nmagnetism has to do with the way electrons in a material interact with each other.  electrons have some basic properties (mass, charge, for example) and also a property called "spin".  \n\nit can be measured that any given electron has what is called a "magnetic dipole moment", which basically means that every electron behaves like a tiny bar magnet.  so the property of "spin" was devised to explain this - if you have some electric charge and move it around in a closed loop, a magnetic field is generated inside the loop.  this phenomenon is called induction and it's the basis for lots of real-life magnets.  this is why you usually see electromagnets made by wrapping wire around in a coil - when you pass an electrical current through the wire, the electrons in the metal basically move in a loop, and this causes a field to form.\n\nanyway, you can think of an electron as a little ball of electrical charge.  if the ball is spinning, then the charge on the ball is moving around in a circle - so this would create a magnetic field.  \n\nanother measurable property of this "spin" is that it is quantized - this means that the electrons can only spin at certain speeds and orientations.  different particles have different spins, and for an electron there are 2 spin states - usually referred to as "spin up" and "spin down" because the axis of the dipole moment points in different directions.\n\nthe difference between the various types of magnetic materials (ferromagnetic, antiferromagnetic, paramagnetic, etc) is in how the spins of all the electrons in the materials are oriented.\n\nin a ferromagnet, the spins are (mostly) oriented so that they're all pointing the same direction.  this causes the magnetic fields from each electron to add up, and you get a large macroscopic magnetic field as a result.\n\nin an antiferromagnet, on the other hand, spins are oriented so that neighboring electrons point in opposite directions.  this is a highly-ordered state, and in many materials only forms when you cool the substance below a critical temperature called the "neel temperature".  above this temperature the random thermal fluctuations take over and the spin ordering falls apart.\n\nantiferromagnetism is observed in transition metal compounds, in particular metal oxides, such as nickel oxide (NiO) or cobalt oxide (CoO).  the behavior of electronic spins are a subject of intense research these days, and so a simple and well-defined picture of their behavior is not easy to come by.  \n\nhowever, it is thought that the long-range interactions of electronic spin is responsible for a number of interesting effects that are being studied in transition-metal oxides.  one well-known example is in the study of high-temperature superconductors, which are often oxides of transition metal alloys.  the electrons involved in the superconducting effect act in pairs called "strongly correlated" electron pairs, and it is thought that the electrons interact via coupling through their spin.\n\nhere are some links so you can learn more:\n\nhttp://ghmfl.grenoble.cnrs.fr/magnetisme/recent5.htm\nhttp://www.jhu.edu/~gazette/2002/30sep02/30magnet.html\nhttp://www-als.lbl.gov/als/science/sci_archive/peem_spin.html\nhttp://en.wikipedia.org/wiki/Antiferromagnetism
529607
If you have access to the Journal of Applied Physics, this should help:\nhttp://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000076000009005380000001&idtype=cvips&gifs=yes
975911
First of all, I'm not professional of physical. I don't know at all, but Iron and steel are really high permeability, and strongly attract to magnet. Seem like the steel bar would tell you which one rely force electron. I don't think Iron has any thing to do with steel.
268419
Methods\n\n\nDiamagnetism\n\nA substance which is diamagnetic repels a magnetic field. Earnshaw's theorem does not apply to diamagnets since they behave in the opposite manner of a typical magnet (relative permeability μr < 1). All materials have diamagnetic properties, but the effect is very weak, and usually overcome by the object's paramagnetic or ferromagnetic properties. A material which is predominantly diamagnetic will be repelled by a magnet, although typical objects only feel a very small force. This can be used to levitate light pieces of pyrolytic graphite or bismuth above a moderately strong permanent magnet. As water is predominantly diamagnetic, this property has been used to levitate water droplets and even live animals, such as a grasshopper and a frog. The magnetic fields required for this are very high, however; in the range of 16 teslas, and create significant problems if ferromagnetic materials are nearby.\n\n\n\n\nSuperconductivity\n\nDue to the Meissner effect, a superconductor also expels magnetic fields (μr = 0), much better than a diamagnet. Due to this (and flux pinning) the magnet is held at a fixed distance from the superconductor or vice versa. This is the principle in place behind EDS (electrodynamic suspension) magnetic levitation trains.\n\n\nFeedback control systems\n\nIf the position and trajectory of the object to be levitated can be measured, the field of nearby electromagnets (or even the position of permanent magnets) can be continuously adjusted via feedback control systems to keep the levitated object in the desired position.\n\nThis is the principle in place behind common tabletop levitation demonstrations, which use a beam of light to measure the position of an object. The electromagnet (arranged to pull the ferromagnetic object upwards) is turned off whenever the beam of light is broken by the object, and turned back on when it falls beyond the beam. This is a very simple example, and not very robust. Much more complicated and effective measurement, magnetic, and control systems are possible.\n\nThis is also the principle upon which EMS (electromagnetic suspension) magnetic levitation trains are based. The train wraps around the track, and is pulled upwards from below.\n\n\nOscillating fields\n\nA conductor can be levitated above an electromagnet with a high frequency alternating current flowing through it. This causes any regular conductor to behave like a diamagnet, due to the eddy currents generated in the conductor. Since the eddy currents create their own fields which oppose the magnetic field, the conductive object is repelled from the electromagnet.\n\nThis effect requires high frequencies and non-ferromagnetic conductive materials like aluminium or copper, as the ferromagnetic ones are attracted to the electromagnet.\n\n\nHalbach arrays\n\nAnother way of stabilizing the repulsive effect is to use fields that move in space, rather than just time. This effect can be demonstrated with a rotating conductive disc and a permanent magnet, which will repel each other.\n\nThis is the principle of the Inductrack maglev train system, which avoids the problems inherent in both the EMS and EDS systems. It uses only permanent magnets (in a Halbach array) and unpowered conductors to provide levitation. The only restriction is that the train must already be moving at a few kilometers per hour (about human walking speed) to levitate. The energy for suspension comes entirely from forward motion, efficiency is good, and no extremely low temperature suspension magnets are required.\n\nHalbach arrays are also well-suited to magnetic levitation of gyroscope, motor and generator spindles.\n\n\nGyroscopic motion\n\nThe reason a permanent magnet suspended above another magnet is unstable is because the levitated magnet will easily overturn and the force will become attractive. If the levitated magnet is rotated, the gyroscopic forces from spinning and precession can prevent the magnet fro
1179277
the importance of physics?? it is very imp cos if there wasn't pysics we wouln't know how things work. there wouldn't be neither electricity nor magnetism. you wouldn't live as comfortable as you live today...is this enough? :)
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There is a confusion about magnetic attration and gravity attraction. First of all,nothing has been proven to show that there is something in the earth that pulls you down.It makes more senseto believe that gravity is an external phenomena rather than an internal one.\n\nThere is no magnetic response unless two poles exist in a material. In this case we have an internal phenomena which has to do the atomic structure of the material which forms\nan external circuit of twisted space. It requires two opposite ends to observe a magnetic response. The poles of a material which is magnetized can exhibit both attraction and repulsion.\nMost material display some magnetism.\nFerrous material are able to store magnetic power more so than other material because of the arrangement of their electronic structures.\n\nIt is believed by scientists that  the magnetism of the earth is caused by a molted iron core;however ,it has\nbeen shown that at high temperature a magnetic field cannot be established.\n\nThe best explanation presented was that the earth magnetic field is caused by the motion of the ocean around the earth.
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http://www.scitoys.com/scitoys/scitoys/magnets/gauss.html\n\nAll the details, tips, and materials you will need. I had great fun experimenting with my first one, making it longer, adding more magnets, larger magnets and bearings etc. I managed to get hold of some great magnets and bearings the same size as a pool ball. \n\nI won't go into detail about what happened to my bedroom wall with that one though, it's another story.\n\nHope you like the site and have fun.\n\nPete.
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Hey there:\n\nInteresting question, because a month ago, i stumbled upon a thrown away harddrive while walking my dog.  I desembled it while I was at home, and found inside it TWO EXTREMELY POWERFULL RARE EARTH MAGNETS.  Also, around on each side of these magnets, was a magnetic shield, that did not allow them to attract from one side, but yes from the other.  If I was you, look for any thrown away harddrive, they all have them, and you will also be getting an extremly powerfull magnet while you are at it.
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as far as i know of, yes.\n\nthink, the man made magnets create their own magnetic field and have always been exposed to the earths magnetic field. Reguardless of the man made one's position, they still emit the same pull towards each other based on their own magnetic fields. Just like magnets work in outer space, they should work at the north and south poles. (also, the man made magnets pull isn't effected when you connect multiple ones together so off of this example, they should work at the north and south poles also.)
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Antigravity, but that hasn't been proven.  Magnetism works when you have two magneticaly charged objects.
1097043
Sorry, but as far as I can tell, it doesn't exist.\n\nThen again, I know nothing about this area of interest.\nI like enio_giacomini's answer. Go with that.\nThen again, he answered that "magnet" question with "In center," which makes no sense at all.  Whatever. Your call.
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The electrons are not attracted to either pole of the magnets. However the deflection of the electron beam follows the same principle as that of a motor, i.e. the Lorenz Force right hand rule (i.e. the deflection of the electron beam is at right angles to both the magnetic field and the direction of flow). Therefore the magnets at the top and bottom of the tube move the beam left and right, while the magnets at the sides of the tube move the beam up and down.
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Experimenting with magnetorheological fluids.\nSuspending a magnet in mid-air.\nLevitating pyrolytic graphite.\nA Gauss Rifle: A Magnetic Linear Accelerator.\nBuilding a Curie-effect heat engine.\nGoing further:\n\nSuperconductors.\n\n \n \n \nThe Gauss Rifle:\nA Magnetic Linear Accelerator\n \n \n This very simple toy uses a magnetic chain reaction to launch a steel marble at a target at high speed. The toy is very simple to build, going together in minutes, and is very simple to understand and explain, and yet fascinating to watch and to use.  \n \n gauss rifle Click on image for animated view  \n \n The photo above shows six frames of video showing the gauss rifle in action. Each frame shows 1/30th of a second. In the first frame, a steel ball starts rolling towards a magnet taped to a wooden ruler. In the second frame, a second ball can be seen speeding between the rightmost two magnets. By the third frame, the accelerator has sped up so much that the ball that is seen leaving the left side of the device is just a blur as it smashes into the target. One ball, starting at rest, has caused another ball to leave the device at a very high speed.  \n \n gauss rifle materials Click on image for larger view  \n \n The materials are simple. We need a wooden ruler that has a groove in the top in which a steel ball can roll easily. Any piece of wood or aluminum or brass with a groove will work. We chose the ruler because they are easy to find around the house or at school or at a local stationery store.  \n \n We need some sticky tape. Again, almost any kind will do. Here we use Scotch brand transparent tape, but vinyl electrical tape works just as well.  \n \n We need four magnets. Most any type will do, but the stronger the magnets are, the faster the balls will go. Here we use the super strong gold-plated neodymium-iron-boron magnets we have made available in our catalog for the other projects. They work great.  \n \n We will also need nine steel balls, with a diameter that is a close match to the height of the magnets. We use 5/8 inch diameter nickel plated steel balls from our catalog.  \n \n The only tool we will need is a sharp knife for trimming the tape.  \n \n gauss rifle first\nClick on image for larger view  \n \n We start by taping the first magnet to the ruler at the 2.5 inch mark. The distance is somewhat arbitrary -- we wanted to get all four magnets on a one foot ruler. Feel free to experiment with the spacing later.  \n \n gauss rifle tape\nClick on image for larger view  \n \n With the sharp knife, trim off any excess tape. Be careful, since the knife will be strongly attracted to the magnet.  \n \n It is very important that you keep the magnets from jumping together. They are made of a brittle sintered material that shatters like a ceramic. Tape the ruler to the table temporarily, so that it doesn't jump up to the next magnet as you tape the second magnet to the ruler.  \n \n gauss rifle two\nClick on image for larger view  \n \n Continue taping the magnets to the ruler, leaving 2.5 inches between the magnets.  \n \n When all four magnets are taped to the ruler, it is time to load the gauss rifle with the balls.  \n \n gauss rifle all\nClick on image for larger view  \n \n To the right of each magnet, place two steel balls. Arrange a target to the right of the device, so the ball does not roll down the street and get lost.  \n \n To fire the gauss rifle, set a steel ball in the groove to the left of the leftmost magnet. Let the ball go. If it is close enough to the magnet, it will start rolling by itself, and hit the magnet.  \n \n gauss rifle ready\nClick on image for larger view  \n \n When the gauss rifle fires, it will happen too fast to see. The ball on the right will shoot away from the gun, and hit the target with considerable force. Our one foot long version is designed so the speed is not enough to hurt someone, and you can use your hand or foot as a target.
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You try what the first poster suggests, but it isn't likely to work well. Besides the danger mentioned of doing damage to the equipment, you will have one of these problems that will prevent the result you want:\n1) the electromagnet won't be strong enough to have any demagnetizing effect at all, \nor,\n2) the electromagnet will completely demagnetize the permanent magnet.\n\nUsually magnetic catches consist of a flat steel plate that seats against two poles of the magnet. A better solution is to put a few layers of tape on the steel plate so that it does not come into contact with the pole pieces. Depending on the kinds of tape you have around, one layer might be enough.\nMagnetic force falls off very rapidly as you separate the surfaces.
198626
You could measure the strength of an electromagnet by hanging small iron \nweights from the magnet.  When the applied weight (force of gravity acting \non the weights) exceeds the force of the magnet, the weights will fall \noff.  Steel Flat washers of the same diameter as the coil would be \ninexpensive and simple to use.  You can weigh several washers on a food \nscale and calculate the average weight of each washer.\n\nThe equation for the magnetic field strength, H0, in Ampere-turns per \nmeter for an empty (air) coil is:\nH0 = the applied voltage / (the number of turns of wire in the coil \nwinding X Area within the coil winding X the permeability of air).\nThe area is pie X D squared/4, where D is the diameter of the coil winding \nin meters.\nThe permeability of air,  , is 4 X pie X 10 to the - 7  henry/meter\n\nThe Equation is for a direct current.  An alternating current applied to \nthe coil cannot be used for lifting magnetic objects.  \n\nBy substituting different numbers for the applied voltage, the number of \nturns of wire and the diameter of the coil, you can calculate how each \nparameter will effect the strength of the magnet.\n\nElectromagnets can be fun, however,  keep them away from recorded tapes or \nthey will erase the contents.