Why aren't magnet generators more mainstream?

Discussion in 'General Science & Technology' started by garbonzo, Sep 14, 2014.

  1. exchemist Valued Senior Member

    Messages:
    12,517
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. leopold Valued Senior Member

    Messages:
    17,455
    Units

    In SI units, B is measured in teslas (symbol: T) and correspondingly ΦB (magnetic flux) is measured in webers (symbol: Wb) so that a flux density of 1 Wb/m2 is 1 tesla. The SI unit of tesla is equivalent to (newton·second)/(coulomb·metre).[nb 6] In Gaussian-cgs units, B is measured in gauss (symbol: G). (The conversion is 1 T = 10,000 G.) The H-field is measured in amperes per metre (A/m) in SI units, and in oersteds (Oe) in cgs units.[13]
    en.wikipedia.org/wiki/Magnetic_field
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. exchemist Valued Senior Member

    Messages:
    12,517
    Exactly. So 10⁴ gauss = 1T, which has the units of N.s/C.m, precisely as Aq. Id said.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    Ok I get it. You have no idea what a college curriculum in electrical engineering entails. That's understandable. But you don't think that's being just a little presumptuous, assuming that it doesn't entail expertise in the subject of motors and generators? And if he's employed by power companies, don't you think they rely on his expertise to analyze motors and generators, the way an auto repair shop relies on a mechanic to change oil, replace water pumps, align the steering, etc.? Would you presume to tell your mechanic how to fix a car (I mean if you felt as certain about it as you do about this topic)?

    You're mistaken. Consider this simple test of your belief:

    1. Start with a small DC generator. Assume it's built like a common motor, the type with magnets attached to the housing and the windings on the rotor.
    2. Attach a light across the terminals. Spin the rotor and the light shines because the conductor is moving against the static field.
    3. Now clamp the shaft onto a large bench vise such that it supports the generator in the air. Spin the housing and the light shines. Yet the conductor is stationary. This time the field varies, doesn't it. QED.
     
  8. leopold Valued Senior Member

    Messages:
    17,455
    billvon,
    will you straighten this jerk out?

    AI,
    the magnetic field of a generator IS A CONSTANT.
    it DOES NOT vary.
    it's the CONDUCTORS that move.
    get over it.
     
  9. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    I was on another train of thought, that the gravitational field g is identical to the acceleration imparted to the mass (such as F = mg) therefore the mag. field is like "acceleration" since it develops force also (in which I would have needed to come up with the analogue of mass for the other terms in the magnetomotive force F = qvB*. If so, then qv is like "mass"). As soon as I wrote that, I realized someone would complain about the units, so I added the caveat. My reason for expressing it in Newtons was that I thought the other question might come up (what the hell do you mean like acceleration), and if so I could work through it: F = qvB ⇒ [C][m/s] [N∙s/C∙m] = 1 N (see that pans out without trying to remember Teslas and Gausses. Note to self: ask Fraggle if it's 2 Gauss or 2 Gausses heh heh) Of course this gets a little weird because if [N∙s/C∙m] is the dual of acceleration then the dual of mass is going to be qv which is in units C∙m/s which looks pretty freaky. And of course the real dual for the B field is the D field (electric displacement) so I'm kind of on the hairy edge of making a plausible analogy. I might get away with calling it a quasi-duality. But my reasoning is that the field should equate to the acceleration, and the mass should relate to the charge (they're both properties of matter), or say proportional to it, making qv a plausible candidate. More to the point: the charge is the thing being accelerated through the mag field, hence, a "quasi-dual" of mass. All the more reason to treat v as a constant of proportionality.

    I'm not sure but I think leopold is a technician. I'm not trying to blow everybody's cover here, but it helps to understand the background that imputes the belief. For example, from your moniker, knowing you're British, I would deduce that you were once a pharmacist.

    Please Register or Log in to view the hidden image!

    It stands to reason you would therefore frown on any post I make which reeks of non prescription meds. But of course that's perfectly fine since that's how all the cranks come across to me (some chemical is involved). But more to the point: a pharmacist is on top of his weights and measures, therefore who but you to certify that the units are correct?

    Please Register or Log in to view the hidden image!



    In any case, I hope leopold gets something out of this little discussion, even if it does flog a dead horse.


    *and since the induced current in the winding is, well: 1 A = 1 C/s, so then we invoke a little differential calculus: I = dq/dt. We need to think this way since I is the perceived output of the transfer function of the device (angular velocity to current). But that leads to other rambling thoughts, so let me just close here.
     
  10. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    Just don't call bill a jerk when he confirms what I said. Of course you could just look it up. I have known this since a child since I had a generator on my bike to power the headlamp. And out of curiosity as to its magical ability to convert angular velocity into current, I took it apart. Guess what I found:


    Please Register or Log in to view the hidden image!



    Of course when I grew up and eventually ended up taking electromagnetics I learned the first principles which you are disputing here. So, as usual, I'm simply correcting the errors as I see them. Nothing to get torqued about, so to speak. We can bicker over God and evolution, but generators are real. And they work either way.
     
  11. exchemist Valued Senior Member

    Messages:
    12,517
    You might read this: http://en.wikipedia.org/wiki/Electromagnetic_induction

    the opening sentience read as follows: " Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field."
     
  12. exchemist Valued Senior Member

    Messages:
    12,517
    Pharmacist? No I'm afraid not. Chemistry degree at Oxford, followed by 18 months training as a patent agent and then 33 years with a major oil company, mostly in its lubricants business.
     
  13. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

    Messages:
    19,252
    Trouble with tribols?
     
  14. billvon Valued Senior Member

    Messages:
    21,644
    Sorry, I can't.

    The critical item in any generator is a wire that moves past a magnetic field. That can be a permanent magnet armature that remains stationary and a wound rotor that moves past it, or a stationary wound armature that holds the wire still while a rotating permanent magnet core moves past it. The case is the same from the perspective of the wire.

    Or the permanent magnet can be replaced by a wound electromagnet, which is the case for nearly all generators (including utility scale generators and the ''generator" in your car.) In that case the magnetic field is not constant, but changes to vary the voltage created by the generator.

    Not true in most cases. It is varied to control the generator's output voltage.
    Also not true in about half the cases out there.
     
  15. leopold Valued Senior Member

    Messages:
    17,455
    well, what do we have here?
    an ALTERNATOR
     
  16. Motor Daddy Valued Senior Member

    Messages:
    5,425
    Which requires no field current from the battery?
     
  17. leopold Valued Senior Member

    Messages:
    17,455
    i knew i shouldn't have gotten into this.
    i want to see some links to these types of "generators" with rotating magnets.
     
  18. Motor Daddy Valued Senior Member

    Messages:
    5,425
    Do a search for TM9-8000. Start learning!
     
  19. exchemist Valued Senior Member

    Messages:
    12,517

    Haha yes we used to keep a handful of tribologists on the research staff - useful for things such as failure analysis and for collaborative projects with machine designers. But I was not one of them.
     
  20. leopold Valued Senior Member

    Messages:
    17,455
    since when does a generator require a field?
    this is EXACTLY why you cannot push start a car that has an wound field alternator.
     
  21. Motor Daddy Valued Senior Member

    Messages:
    5,425
    You didn't read TM9-8000.
     
  22. leopold Valued Senior Member

    Messages:
    17,455
    provide the link, and i will.
     
  23. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

    Messages:
    19,252

Share This Page