Can Magnetic Repulsion be Increased?

http://en.wikipedia.org/wiki/Electromagnetism

Look up Halbach effect. A geometric arrangement of individual magnets that creates a single pole magnet with double the field strength of the original magnets. A very interesting concept.

Someone are thinking still in the world. Congratulations. Good idea ! acquaway@acquaway.ind.br

This is an addon question, but can magnetism be reflected?

As far as I was aware no (interacting of the weaker and stronger fields causing degrading of the permanent magnet field strength and such). This would be a simple experiment to do thou to prove if it does or doesn't work. All you need is a weak bar (or horseshoe) magnet, some insulated wire to create the coil, and a DC power source such as a battery. If interested further, you could replace the magnet with a rod of iron (a good core for an effective electromagnet) and redo the experiment, this should give you the strongest magnetic field. Let me know what the results are, its one of those things I have been interested in doing but have never got around to.

Your best bet is likely to either go for one or the other. Electromagnet will likely be your best bet (and more fun to implement too).

Have fun, it's how you learn.

even i have a similar doubt but the case, what i felt was it might be increased in case of electro magnets where the magnetic permeability is in your control as u increase the current the field increases (my assumption, pls say if it is wrong)

Hi Outofthebox, you asked

"Can you increase the strength of the repulsive force with electrical current?"

Well the short answer is yes. There is however a but.

To understand what is going on you will need to refer to the diagram on the right.

To start with we have a piece of magnetic material that is not yet magnetized and has a coil of wire wrapped around it. Now the vertical axis shows magnetic flux or the strength of the magnetic field and the horizontal shows the current flowing in the coil.

Since our piece of metal isn't yet magnetized and we haven't yet applied a current to the coil we are at the origin or where the two axis cross.

As we start to increase the current in the coil the strength of the magnetic field will increase along the red line until it reaches point a. This is where the material is saturated and any further increase in current will not give a further increase in magnetic field strength.

Now if we reduce the current back to zero the strength of the magnetic field will also reduce but now it will follow the green line till the current is zero at point b. Note that when the current reaches zero there is still a residual magnetic field. This is what happens with a permanent magnet.

Now if we reverse the current the magnetic field will continue to decrease following the purple line until there is no magnetic field left at c. If we continue to increase the current the magnetic filed strength will increase in the reverse direction until it saturates in the reverse direction at point d. Again any further increase in current will not produce a further increase in magnetic field strength.

If we now reverse the current so that it flows in the forward direction again the strength of the magnetic field follows the blue and then red lines until it saturates again in the forward direction at point a.

This is called hysterisis and the amount magnetic field that remains depends on the material the magnet is constructed of and what you intend to use it for. For example if it were a core for a transformer you would want as little residual magnetic field as possible as this residual field needs to be overcome before the magnetic field can reverse. If however you are making a permanent magnet you want the maximum residual magnetic field you can get.

Lets now go back and look at what has happened with our permanent magnet. The magnetic field increased along the red line and then relaxed along the green line till it reached point b on the graph. This left us with a certain amount of residual magnetism. If we now increase the current in the forward direction then the magnetic field strength will increase back along the green line but only till it saturates again at point a.

So the answer is yes but only till the magnetic field saturates and the amount we can increase the field depends on how much residual magnetic field that particular material had.

You added the question;

"This is an addon question, but can magnetism be reflected?"

Again the answer is yes but. If you take a magnet and place it on a superconductor it will induce a current in the super conductor and this current will in turn produce a magnetic field opposite to the original magnetic field. Since this is in the opposite direction it will try and repel the magnet. In a way this is sort of reflecting the magnetic field and if the magnet is strong enough it will levitate. Since s superconductor has no resistance to the current you induced in it the current will remain flowing till either the magnet is removed or the material stops being a superconductor.

If you follow this link;

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/maglev2.html

it will take you to a couple of short video clips that show a magnetic field being reflected by a superconductor.

So the answer to both questions is yes and I hope this has explained the but part.

Thank you for your ideas. I am realativly new to these concepts and being a very visusal learner, I need to see things in order to fully understand them. For example, the wire coil and its application. I know this is a baisic electrical concept, however I'm not sure how it is applied in the context of your answer. Your graph really helped me understand how the current flows, but can you direct me to a source to help visuallize the coil idea? Also, I'm not sure I uderstand how the magnetic feild is pushed in one direction with an electromagnet or is it that the current simply creates north and south poles? Can one ploe be stronger then the other? Can you apply current to a Halbach array and increase the field on one ploe?

Sorry for the simple minded questons but I have a real need to wrap my head around this.

Thanks

Hi Guest, you asked

"I'm not sure I uderstand how the magnetic feild is pushed in one direction with an electromagnet or is it that the current simply creates north and south poles?"

Don't panic I guarantee that the majority of people wouldn't know how the flow of electricity relates to magnetic fields. I also believe that in many cases a diagram or picture is the easiest way to convey what you are trying to convey so here is a diagram.

If you look at the three arrows on the left and imagine that they are all at right angles to each other. If an electrical current flowed in the direction of the RED arrow then it would generate an electric filed in the direction of the BLUE arrow and a magnetic field in the direction of the GREEN arrow.

The right hand image represents a ferrous rod with a coil wrapped around it. It shows the polarity of the voltage applied to it ( + - ) the direction of the current through the coil (red arrow heads) and the polarity of the magnetic field ( N S ) that current flowing through the coil generates.

"Can one ploe be stronger then the other?"

Well not really because it is associated with the same electric fields and current. It can however be spread over a greater area so may not be as strong at a particular point but when taken over the entire area the total field is the same.

"Can you apply current to a Halbach array and increase the field on one ploe?"

Yes you could but the alignment of the coils would be fairly complex and I am not exactly sure of how to achieve it and how the magnetic fields would interact. Calculating the interaction of magnetic and electric fields and the current can be complex and involves some fairly complex mathematics. Just as an aside the core of a stepper motor is specifically magnetized in a way not too dissimilar to a Halbach array.

If you aren't well versed in calculus and are just starting out with understanding electromagnetism then I would suggest that you hold off a little till you have a good feel for electromagnetism before jumping into the analysis of things like field strength a force.

Thank you very much for your imput! You have been extremely helpful with your explantions and I have taken my idea in a completely new direction.

Thank you

How do you calculate the levitating force of an halbach array passing over a shorted coil or capacitor at x speed.

Thanks

Ron

You calculate the force that would be caused by each individual magnet if they were on their own then do a vector summation of the individual forces. It looks very messy on paper but it's really no more than an addition of the individual forces.