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Homopolar generator information

  1. Nov 21, 2003 #1

    I looked for information about how the homopolar generator works, because there are some claims (N-machine, Space Power Generator...) that say there is no backEMF or opposition to obtain the work.

    The homopolar generator is a disc magnet glued to a conductor disc. When you make it turn, there is a EMF between the axis and the periphery of the discs.

    Well, we usually explain the working of the motors saying that a change of magnetic flux causes a current on coils. The magnetic flux change is the method we normally use to move the electrons.

    On the homopolar generator, the magnet does not impulse or move the electrons of the disc. A motor moves the disc and the magnet, so the electrons of the disc move. The only difference with normal motors is the method to impulse the electrons. The homopolar generator does not use the relative movement respect the magnet, it uses the relative movement respect the motor.

    On this page there is better explained all the forces and energies involved (sorry, in Spanish, but the drawings and the formulas should help):


    Well, finally it's stated that it's just like the linear version of the experiment, but on a rotary fashion.

    But i'm not so sure. My question is about the current supposed to run on the radius of the disc, that is supposed to create the opposite torque to the motor.

    On the linear device, the electrons that run through the rod creating the current are the same electrons (they have PERPENDICULAR velocity to the path, but they feel an EMF ALONG the path, and they move in a current ALONG the path, so they finally create backdrag also).

    But in the homopolar generator, every moment, the electrons that creates the EMF from the radius of the disc are different ones (they have a velocity PERPENDICULAR to the radius, so they feel an EMF ALONG the radius, but they finally move PERPENDICULAR to the radius).

    My question is:

    Stated that the electrons on the radius are not the same every time step on the rotary disc, can we consider that it is a real current?, is really a current running through the disc radius?
    Last edited: Nov 21, 2003
  2. jcsd
  3. Nov 21, 2003 #2
    Other interesting thing about the homopolar generator is that it can work also as a motor:

    If you apply EMF between the axis and the periphery, the rotor start to turn, due to the existence of the B field of the magnet, and so, the electrons begin to move.

    On normal batteries and circuits, the moving charges must be replaced by the EMF source (because the movemnet of the charges is ALONG the path. Finally, the source of EMF goes empty.

    But what happens on the homopolar generator working as a motor?

    The electrons always follow a PERPENDICULAR path to the aplication of EMF, and also, the electrons that left the radius are replaced by more electrons from the conducting disc, so it seems that the EMF source will not get empty!.
  4. Nov 21, 2003 #3
    Last edited by a moderator: Nov 28, 2017
  5. Nov 21, 2003 #4
    Hello Boulderhead.

    I checked your links (some i've checked yet before) and other ones new.

    On your topic you say you are skeptic by some reasons. I'll thank you to post your reasons on this topic.

    I'll tell somethings i think about this term:

    Firstly, I don't understand the sentence on much of the pages where it's said that it's not easy to understand (or is not contempled by clasical electromagnetism) that the magnet attached to the rotating disk produce EMF, because there is no change on magnetic flux to get the EMF.

    That method is not used on the homopolar generator, but the mechanism to get the EMF is explained on clasical electromagnetism:

    everytime you've got a moving charge and a magnetic field, an electric force is generated in some direction (so is not necesary a moving or changing B field).

    Nobody said that the only method to move a charge were the magnetic flux change method.

    Also, on the clasical example that relates the flux change with the generation of EMF, the same principle is being used. If you move one rod perpendicular to a uniform B field, no flux is changing, and also, the EMF is created. Of course, if you connect the rod with a circuit, it's clear that the space between the rod and the rest of the circuit will change (you've got to move the rod somewhere!). If you move all the circuit behind the B field, the EMF on some parts will cancel on others.

    That change on surface to the conections is something that doesn't happen on the rotational example. It's not needed a change on the flux. That only happens on the linear version of the experiment, and i think it's just a consequence of that kind of motion (that's to say on normal motors induction also, because of the change of normal surface to the magnetic flux).

    Other point about the homopolar generator:

    I said before that i think no current is on the radius of the rotor. If so, maybe the current should be on a circular path, due to the rotational movement we are doing to the disc. But moving the disc, you move the charges on one direction... ALL the charges (positive and negative), so there is no current on the disc, because all the charges move on the same direction. A current is a displacement of negative charges to one side, then, the positive charges to the other side. If ALL that charges move on the same sense, no current is created.

    And finally, viewing the homopolar generator as a motor, if you apply an EMF between axis and periphery, you'll obtain positive charges moving on one sense, and the negative ones on the other. That will create a current rounding the disc, but i dont know if this current will make the rotor move. Also, this circular current will create an EMF force around all the disc, centered and in opposite direction to the EMF applied.

    Maybe the configuration and working of this device is not free energy or overunity, but in some way, it's strange and astonishing.
  6. Nov 22, 2003 #5
    I have heard these claims and done many experiments, and all point to the homopolar generator not working. Any measured voltage seems to be due to jumpy contacts and the relative motion between the contact leads and the spinning magnet. The experiments I have performed aren't very accurate, as I really didn't need to know the numbers unless something happened, and nothing interesting or unusual did. But I have not conclusivly proved there is nothing to the claims, just that I couldn't replicate it with my modest budget and resources.
    I do have an interesting idea on a related device that works again using the as yet untested by me Tesla bifilar coils. However, when I get around to it I will not use that idea, prefering the motionlessness of the transformer one previously descrbed. But I'm getting off topic.
    Cala, I suggest you take some physics classes rather than ask about every overunity scheme you find on the net, it will take years to test and answer them all, not to mention that you have a much greater chance of being told they don't work here, regardless of whether they do or don't. Note that I'm not accusing anyone of unscientific bias, it's just that most people who visit physics forums understand and accept current physics and by definition therefore do not consider systems which should run by the normal laws as being capable of overunity, which the normal laws forbid.
    That, getting off topic again, is the greatest reason why I consider the Tesla bifilar coil as being a real contender, because Tesla actually suggests (implicitly) in his patent that the coil doesn't follow the normal laws, and so may therefore somehow circumvent the CoE law.
    Last edited: Nov 22, 2003
  7. Nov 22, 2003 #6
    Jonathan, i'm only trying to see if all that overunity and free energy devices can be seen from the point of view of actual physics (on my limited view).

    in this case, I just make the analisys of force related to velocity and related to magnetic field, they all orthogonal, and the results seems to be strange ones. Do you remember that i said that if you applied EMF, a current will flow on a circular path, and will create a radial EMF opposite to the applied EMF?... Actually, the EMF created is ON THE SAME SENSE than the applied!!!

    The analisys is very easy to do under clasical physics, but the results seem not to agree with it, so I only want people more skilled than I to analyze the homopolar generator on all the cases that I pointed out, and tell me if their results agree with i said or there is something i'm not counting, and what it is. I'll try to do some drawings to explain myself.

    I'm not looking for a new physics theories, i'm looking for new physics results.
  8. Nov 22, 2003 #7
    This is why I suggested you take a physics class: because the right hand rules, etc. do agree with current physics and this device doesn't agree with them, and your interpretation of them is incorrect.
    If you pass a current radially through the disk, there will be a force to make the disk and magnet rotate relative to each other. But unless this force is of such unbelievable strength as to break the bonding agent used to hold the disk to the magnet, it will not spin, becuase the bonding agent eliminates the possibility of relative motion. Of course, if one did the experiment hoping it would move, one would have contacts on the rim and the axle. And the wires connected to those contacts will feel a force, and supposing they're held down, will exert a force on the whole assembly, making it want to turn relative to these two wires, though it is almost always not of enough strength to over come bearing friction. (Notice though, that though I say two wires and we know they must have current traveling in opposite directions, their effects don't cancel each other out completely because one comes and touches the rim, while the other must go right across the B-field to get to its contact, giving it more direct interaction with the assembly than the first.)
    The claims I have heard are that the device generates electricity when rotated despite the fact that there is no relative movement between the parts, and this contradicts current physics. The proponents have said that this is due to the unrecognized fact that when one spins a magnet on a the same axis as it is magnetized on, the field doesn't spin with it. They assert that magnetism is an effect of the spacetime occupied by, and apparently inseparable from, the magnet.
    None of my experiments have pointed in this direction. One did a little, but I think it was due to the magnet's nonuniform field, but I have no way to test and see if it really has enough of a nonuniformity to cause me to notice. It is a cheap magnet though, not designed for physics experiments like this, esp. givent he smallness of my set up.
    I encourage you to do your own experiments and see, since mine aren't conclusive.
    Last edited: Nov 23, 2003
  9. Nov 22, 2003 #8


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    I didn't read all the posts or check the links (maybe tomorrow) but I am reminded of the experiment in physics class where you drop a magnet down a metal tube (non-ferrous). The magnet drops slowly because as it drops it induces a current and magnetic field in the pipe. The current is on the order of a few THOUSAND amps. Enormous. But free energy? No.
  10. Nov 23, 2003 #9
    No, I think that is almost completely unrelated. The electrical energy is due to the kinetic energy of the magnet which is from the potential energy you put in. I'm sure we all agree on that.
    This thread, as I understand it, is about whether or not there is any truth to the claims that homopolar generators can put out more enrgy than they take in. My experiments, though inconclusive, generally point to no. Accepted physics, as what I can tell of what cala understands, is not completely understood by cala (no offense of course).
  11. Nov 23, 2003 #10
    Jonathan, you don't see that in the case of the homopolar generator, it will work the same with the disc in relative motion to the magnet or with the magnet attached to the disc. In this case, the relative motion about these parts is not the prime mover. The prime mover on the homopolar generator is the motor that applyes the torque to rotate the magnet and the disc.

    The electricity obtained by the method of relative motion of magnet and wires is a consequence of the physic principle better used on the homopolar generator: i think it's like the poynting vector. The relative motion method is a subset or subclass of this poynting vector like method. So finally, you can have electricity with no relative motion between B and the charges, but you need to move the charges by another method, and it's done with the motor. The magnet and the disc can be moved by the motor, and this will also create EMF because the charges have velocity into a B field,so EMF is then created, and it's clasical physics.

    Also, take notice than on all the physics books, the principle of this moving charge into a B field creating a force is always explained before the flux variation and relative motion method, so to me, this relative motion method is derivated from this primordial fact used to get the electricity on the homopolar generator.
  12. Nov 23, 2003 #11


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    Save yourself a lifetime of effort and accept the first law of thermodynamics.
  13. Nov 24, 2003 #12
    Well Russ, first, let me try a final (and a bit extense) explanation of the homopolar generator under clasical physics. Then, put the first law of thermodinamics where you consider it comes into play.

    I'll put a detailed explanation on what I think is happening on the homopolar generator, and it could be true that it could be more output than input, without strange energies coming from nowhere:

    First, i’ll make a little change on design. Imagine the rotating conducting disc, but only a radial region is under the B field of a magnet (the magnet is not attached to the disc also). The reason to do this change will be lately exposed.

    When the motor gives torque to the disc, the situation of moving charges into a B field will happen, so a radial EMF will be created under the B field affected zone. Now, we connect the periphery and the axis of the disc with an external circuit, closing the circuit through a radius on the B field affected region of the disc.

    Due to the EMF created by the moving charges on the disc under the B field, a current is created on the circuit, but this current (in principle) can't go through the radius of the disc under B field, because the charges move perpendicular to the radius in the disc on this zone, as previously stated.

    So how can be a current through the circuit and no current running on the disc radius?.

    Well, the disc is neutrally charged (the charge is equally distributed), but due to the rotation and the EMF created, the negative charges take the external circuit path to go to periphery of the disc, and the positive ones go through the circuit on opposite direction to the center axis of the disc. The periphery of the disc becomes negatively charged , and the axis positively charged as the charges pass through the circuit. Then, a polarizing current that polaryzes the disc runs through the external circuit (this polaritation will be recombined on all the disc parts unafected by the B field, as exposed later, but now, we will consider that the disc remains polaryzed to explain what happens on the B field part). As the disc goes polarizing, a radial E field goes increasing by polarization of the disc, and this E field has the same sense than the one created by rotation of the disc on B field zone. This new E field will add to the one created, so rotation and polarization of the disk work together on the B field zone. Now, the E field is greater than the one created by particle movement, so the movement of the charges is affected, and now, a radial component of the charges movement is generated by the polarization effect on the disc B field affected zone. Now, a current is allowed to flow radially also throgh the B field zone. This current will tend to recombine the charges distribution on the disc to make it neutral again. This recombination current take place radially around ALL the disc. This current was always present on the disc part not affected by B field, and now, could also be generated on the B field zone, if the recombination is slower than the polarization, as exposed.

    The important fact is that ALL the charges to polaryze the disc must go through the external circuit (so huge current on the circuit), but the same huge current must redistribute through ALL the disc radius to recombine the charges against disc polarization, and only a little portion of this current (if any) pass through the radius affected by the B field, (so little current through that specific radius of the disc will cause an EMF opposing to the motor torque).

    That is the reason to change the design of the homopolar generator: If all the recombining currents of the disc were under the B field, the EMF generated against the motor torque will count, and the output will be the same than the input.

    But current under B field creates EMF, and current alone does not generate opposition, so distributing the same huge current that run through the circuit through the disc, causes that only a little portion of the huge current go through the radius under the B field, and that reduce the quantity of EMF that the motor must to overcome.

    So the current to polaryze and depolaryze the disc has the same amount, but the disc polaryzes through the external circuit (all that current runs on the circuit), and the disc depolaryzing current runs through all the disc radius, and only a little portion of the total current ( only the part under the B field ) causes a force opposing to the prime mover motor.

    As you can see, if the radial depolaryzing current is 1A on each radius of the disc (for example), then we could have a polarizing current of 2*PI A on the circuit at the same time (every point of the periphery is neutralyzed at the same time). Theoretically, we could get an output/input ratio of 2*PI=6.28... or 628 % eficiency. The bigger the B field region, the less eficiency (because we have to take more recombination currents into the tangential EMF calculation), and sustract all the looses.

    Russ, I think the homopolar generator acts just like an open system, not like a closed one ( like all the motors and generators we use ), so the thermodinamic law you talked about doesn’t apply here.

    The conducting disc has a part that is part of the electric circuit, creating the EMF under the B field, but also have another part that receives different charge distribution, and works recombining without opposition, because the currents on this part are not under B field. So that part is just a surrounding environment to the active parts, and restores the effects made by the B field part and the circuit, taking advantage on the fact that the recombination current that occurs on this part of the disc ( making the charge distribution neutral again to repeat the procces on active parts by rotation ) has no back-effects from the point of view of the motor prime mover, and so, the motor that gives torque only have to apply the work that will be involved on the active part energy exchanges of the disc. The energy exchanges on the part of the disc that is not under B field are “free” from the point of view of the active parts, and that is to say, on the motor that impulse the disc.

    Now I see why on normal circuits the work we must do is the same than the work we can get, and we can never get more than 100% eficiency: because the polarization (EMF source) and recombining (external circuit) currents run through the very same conditions!.

    On the homopolar generator, the polarizing current pass through the external circuit at a time, but this current is fractioned to fill every radius of the disc on the recombining step, and only works against the motor torque if it’s under the B field part. So we use only one circuit to make all the polarization current run to the disc, and we collect only a little portion of radial recombining current on the disc active part. So it's to say, we see a certain amount of EMF and huge current through the external circuit, and we get the same EMF, but little current on the active radius under the B field part, and then little torque opposition to the motor, that only have to work to supply the energies involved on the active disc part, not on the rest of the disc exchanges of energy.
    Last edited: Nov 24, 2003
  14. Nov 24, 2003 #13
    Image is better than thousand words:

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  15. Nov 24, 2003 #14


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    All "open" means is that heat/energy can flow throught the boundaries of the system and ny system can be open or closed based on how you define the system. For example my desk lamp here is an open system. It produces light and heat without doing any mechanical work inside the lamp.

    A heat pump is an open system where overunity efficiency sometimes causes confusion. Its confusing because a typical thermodynamic system involves heat (or electrical energy) in, heat out, and mechanical work out. Efficiency is simply Wout/Hin. But a heat pump (and an air conditioner) moves heat around instead of producing mechanical work (or converting heat, in the case of a simple electric heater). The output heat is greater than the input electrical energy, but that is NOT overunity efficiency and the first law of thermo still applies. To avoid confusion, its usually termed "coefficient of performance." And the conditions are known: ie, the heat it moves from the environment into the system is quantifiable and quite well understood.

    So: Where does this energy come from in your systems? And don't say its irrelevant - if its relevant to me, its relevant to anyone who would ever buy one of your inventions.
  16. Nov 24, 2003 #15
    Russ, you're right, the homopolar generator can't go against the 1st law of thermodinamics (as any device can go against it).

    I thought you was talking about the second one, but later I decided to let my error there to get a faster and stronger response.

    So we are in agreement that the homopolar generator can go against the second one... but how?

    Take a look to the image i attached at the initial post on this page.

    Consider the working of the homopolar generator like a serial to pararel conversion on a transfer of charges.

    On the circuit, the charges have a serial transfer fashion, and on the whole disc, the charges have a paralel transfer fashion.

    Now, you can see that given a certain time step, the speed needed on the serial path is much greater than the speed needed on the paralel paths to carry the same amount of charges to the same place. The only difference is that on serial path, the charges goes arriving one by one, and on the parallel path, they arrive all at the same time.

    You can use this fact , and keep a high velocity transfer of charges on a serial path (the circuit), using the parallel paths to go back to initial conditions (the disc axis and periphery).

    The trick is that only one (or some, but not all) of the parallel paths taken by the charges oppose to the prime mover that keeps the whole thing working.

    We can get volts by storing one kind of charges on some place, and other kind on other place, but the current through this places will make the store finally get empty, so the volts dissapear.

    But the homopolar generator does not use the charges that create the volts to create also the current. The charges that creates the volts are different ones than the ones taken into the circuit current, so the volts can be maintained, and the current can run also. To keep the voltage, you only must maintain the speed.

    The current on circuit is on a serial path (so high amount of current as charge/time) and the current on the disk is taken a lot of paralel paths, where only a few ones make resistance to the rotation that keeps the voltage.

    That is where the difference on energy cames from. the charges that creates the EMF are different than the charges collected to make the circuit current. The motor speed gives the EMF created, but the current is marked by the circuit resistance, and the collection of this current charges from the disk does not affect the EMF generation. So we are "de-coupling" the correlation between current on circuit and EMF source. Once you can do that, the currents on the source of the EMF and on the circuit can be different (as explained by the serial and paralel paths examples), and the output energy be greater than the input.

    I've got to think more the way to explain this fact, but now i think i understand the proccess very well, and sure it works. I only have to get an easy example to explain myself.
  17. Nov 25, 2003 #16


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  18. Nov 25, 2003 #17
    Well, i'm sorry, i talked under your point of view, and i had not license to do that.

    Ok, so you think the system can't do more output than input COP.

    Yesterday I was thinking how to explain the working of the homopolar generator on an easy way. A lot of things came to my mind (i could not sleep yesterday), and one thing that came to my mind was the Maxwell Daemon example.

    Here, i put just an ad-hoc explanation of the Maxwell Daemon from a web page:

    "Maxwell was a famous scientist who discovered electromagnetic waves. But only theoretically; he could not prove it. It was proven by Heinrich Hertz 20 years later. But Maxwell put forward a theory saying that in the world there must be something called electromagnetic waves. There is a famous second law of thermodynamics which states that in each system, energy must be constant. But Maxwell said, imagine two spaces: between the two spaces you have a door with a little slit. One space filled with gas is very hot, and the other is very cold. According to the law of thermodynamics, when such a door is opened, both spaces will be of equal temperature. But Maxwell could mathematically prove that the hot space would become hotter, and the cold space would become colder. So this was a riddle, a paradox: Maxwell's daemon.(...) But then along came Zurek, a scientist, who wrote an article in 1984, "Maxwell's daemon, Szilard's engine and Quantum measurement." He solved the paradox in such a way that it could even obey the second law of thermodynamics. He said, this daemon is doing work - Somebody is doing work. Even when he just counts molecules, this also uses energy, this also uses information. So when something is becoming hotter, and something is becoming colder, we can exactly measure this difference of energy, and we can say this is an amount of information, that is energy which the daemon uses for himself. So we could explain it even within the second law of thermodics. He calls this daemon 'Quantum daemon.'" Peter Weibel, "Ways of Contextualisation," Place, Position, Presentation, Public,(ed. Ine Gevers), De Balie, Amsterdam, 1991-1992, pp.232-3.

    Ok. Russ, now imagine the conducting disc of the homopolar generator as a "charge gas". positive and negative particles are there, but they are mixed and externally, the disc is neutral, but internally, the particles are there for the daemon.

    We always see this daemon as something intelligent that not only have to count the particles, in order to get potential, it should recognyze them, and order the particles depending on their charge, changing also their location.

    But on the homopolar generator, our "maxwell Daemon" is just an autistic one: We help the daemon, and create a zone on the disc (by the B field and velocity of the disc) were the daemon have not to move any single one of the particles passing under the B field. Our daemon only have to count the positive and negative particles to create the EMF!.

    I mean, the "charge gas" is neutrally distributed on the whole disc, but as we make the disc rotate, there is a specific radius on the disc (under the B field) where the existence of this particles is taken into account. Imagine that this special radius is a kind of toll or frontier where we have our Maxwell Daemon. As the disc moves, the neutral "charge gas" of the disc goes passing through the toll. Then you have the daemon saying:

    659 positive charges, 678 negative charges - 0.080 V (for example)
    698 positive charges, 687 negative charges - 0.081 V
    645 positive charges, 643 negative charges - 0.079 V

    He must do nothing else to get potential! he have not to move the charges. If we take the Zurek explanation, the work or information than the Daemon must have on these conditions is less than if the Daemon had also to move the charges depending on their charge type.

    I have other examples, and you can't imagine how clear now I see some other ideas that use a similar principle on other physic concepts.

    For example, i tried to do an homopolar generator rotating water analogy, and then it reminded me the experiments of Viktor Schauberger, a man that is known on the free energy world by claim that vortex of rotating water can also extract more output than input.
  19. Dec 10, 2003 #18

    Long time without any comment about this. Well, i'll now risk myself with some calculus. Tell me if you see some errors or simply have something to say...

    the explanation on how the homopolar generator works was early exposed. Now, let's use some equations and parameters:

    Imagine a conducting disc that weights 0.02 Kg. The conducting disc has R = 40 cm. Also, this conducting disc is turning at W = 27 rad/s = 257.83 RPM.

    The disc is turning into a B field of 0.2 Teslas, and the magnet that gives the magnetic field covers 1/16 of the disc surface.

    A conductor with a resistance of Rc = 0.000185 Ohms is the electric circuit that links the periphery and the center of the disc.

    The physical parameters described are:

    B = 0.2 T on 1/16 of the circular area of the disc.

    m = 20 g = 0.02 Kg
    R = 40 cm = 0.4 m

    Rc = 0.000185 Ohms.

    Now, lets make some calculus of the electric power we can get:

    V = 0.5 * B * W * R * R = 0.432 Volts

    I = V / Rc = 2332.8 A

    Pe = V * I = 1005 W = 1 KW

    Now, the portion of current on the disc behind the magnet oppose the movement of the disc:

    Iact = 1 / 16 * I = 145.8 A

    Me = 0.5 * Iact * B * R * R = 2.332

    That is the mechanical force we must to do also:

    Mm = m * W * W * R * R = 2.332

    So finally, we have a mechanical power of:

    Pm = Mm * W = 62 W

    So, finally, the power gain is:

    Pe / Pm = 16

    We can get 1KW of electric power with 62 W of mechanical input!

    Some technical considerations about the device (how to collect the high current, how to reduce this high current-low voltage DC electric energy to normal or usable values) have now to be taken, but the calculus agree with spected theory.

    If the whole disc surface is covered by the B fields, the EMF will be the same on every radius of the disc , but ALL the disc currents will create an opposition that will cause the mechanical input work to be equal than the total electric energy obtained.

    But if only a portion of the currents on the disc take place under the B field, the EMF on this zone will be the same than before (so the electric energy on the external circuit is the same also) but only a portion of the currents on the disc will opose the disc movement, so less mechanical input is required to obtain the same electric energy output.

    The ratio between the conducting disc area and the magnet area gives the gain on energy, or the electric / mechanical ratio.
  20. Dec 11, 2003 #19
    Now we can see two distinct methods to get electric voltage:

    The "standard" method is having an ordenation of charges of different types on different locations of space. That is creating a "dipole", or having a polarized element (like a capacitor). So we can say that an specific static ordenation of charges causes voltage. The voltage is maintained if the ordenation of charges is maintained. In this case, we have a pre-polarized device.

    Also, there is another method to obtain voltage, that is used on the homopolar generator: An specific movement of charges under specific conditions (the B field) creates voltage. The voltage is maintained if the movement of charges is maintained. We have no polarized device.

    What happens if we have electric current on the "standard" method? The current re-order the charges, and the specific ordenation of charges needed to keep the voltage drops down, as the charges go from one side to the other. We are depolarizing the device. The voltage can't maintain, because the current affects the charges ordenation. The device was pre-polarized, and the current de-polarizes it. V is I dependent in such a way. The I we use on circuit is this de-polarizing current.

    What happens if we have current on the homopolar generator? The current also re-order the charges, BUT THE ORDER OF THE CHARGES WAS NOT THE CAUSE OF THE VOLTAGE. The charges can re-order, but there is also the movement of the charges than before, so voltage remains. The current in this case is not depolarizing the device, in fact IT'S POLARIZING IT!. We have voltage due to the movement, and new voltage on the same way, due to the polarization by the current. On normal method, the new charges added by the current tends to compensate the previous ordenation of charges, so finally, the voltage drops as the charges mix. But on the homopolar method,there is no previous ordenation of charges, so the charges re-order and goes acumulating, creating new voltage by re-ordenation, because there is no previous ordenation to deplete. The voltage now is due to the movement and to the ordenation.

    The V and I in this case are independent. The pass of current through the circuit does not affect the creation of the V method by movement, only the polarization effect. That’s the part that is used always on normal method.

    On "standard" method, we have only the de-polarizing current (once the device is pre-polarized).

    On the homopolar generator, we have two currents: One runs through the circuit, and also polarizes the disc, and other runs through the disc, and de-polarizes it. The homopolar generator is doing both proccesses at a time, but on different parts. Also, the real cause of the voltage (the charges movement, not position) is not affected.

    On "standard" method, the depolarizing current is also the current that we must take into acount to get the loses or the input work. (because we could get only the same energy that previously polarized the device).

    On the homopolar generator method, we have two different currents at the same time (in principle of the same amount, one counteracting the effects of the other.) , and we use the polarizing current to get the output, but only a part of the de-polarizing current counts on the loses or input work.

    In fact, the depolarizing current on the disc is free, and the little the active part on the disc (the region affected by the B field that creates the EMF) the greater the energy gain. Polarizing and de-polarizing currents will have the same amount, but not the same effects on the device.

    On the “standard” method, the cause of V is the charges position, a current running will kill this cause of V.

    On the homopolar generator, the cause of V is the charges movement, a current running will re-order the cahrges and create another cause of V that will add to this cause of V, and another current will kill the cause of V due to re-ordenation, but not the voltage due to movement. So finally, we have currents that not depletes the primary source of the voltage (the movement of the charges, not their ordenation).

    Finally, the currents only affects the ordenation of the charges, so if we use the standard method to get potential, it’s easy to understand why we can’t get more output than input, because the cause of the voltage and the cause of the current is the same thing: the modifications on ORDENATION of the charges.

    On the homopolar generator, the cause of voltage is the charges MOVEMENT, not ordenation. The currents created affects only the charges ordenation, not their movement, so the cause of voltage (charges movement) is different than the effects of the currents (ordenation changes).
    Last edited: Dec 11, 2003
  21. Jan 3, 2004 #20
    OK, let's make this simple. A homopolar generator is a proven electrical generation device. What makes it different is that a "normal" generator produces more voltage than current. A homopolar generator produces more current than voltage.
    The "power factor" remains the same, but a homopolar generator is useful in special applications requiring high current/low voltage.
    That's all. Sweet and simple.
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