1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

One of my first theories

  1. May 7, 2004 #1
    So don't be surprised if it's crap.In fact I know it's crap,I just need proper physics people to confirm it's crapness. :redface:
    Think of a hollow cylinder.There are springs on the bottom and top surfaces of the cylinder,meaning that if a ball was inside it would bounce back and forth.It is filled with oil(assume no air bubbles),and the springs are charged.One is positive,one negative.A metallic/magnertic(not sure myself on the material,you choose! :biggrin: ) sphere is in the cylinder.It is charged, pos/neg and so is repelled by one spring and attracted by the other.Actually when I say 'spring' might be a set of springs.Anyway,supposedly the upthrust of the oil will make up for the gravitaional effects on the sphere,and the sphere will be always on the move up and down.Wind a coil around the cylinder and you are producing an induced current.
    OK that was the theory-now please take it easy.I know you're probably pissed off with a lot of ridiculous/silly things here....
    I look forward to have you physics people explain to me all the reasons why this wouldn't work.
  2. jcsd
  3. May 7, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What is this supposed to do?
  4. May 7, 2004 #3


    User Avatar
    Gold Member

    my first guess, perpetual motion.
  5. May 7, 2004 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I was thinking maybe, Milkshakes?
  6. May 7, 2004 #5
    It produces electricity by itself.Supposedly.But come on,I mean it can't possibly work so can someone explain why?
  7. May 7, 2004 #6


    User Avatar
    Science Advisor

    First let's see if I understand what it's supposed to do, and then we can see if and why it don't. The ball is charged, and therefore magnetically attracted to one end of the cylinder, right? And once the ball is drawn to that spring, what then? Are you thinking it might discharge and thus be repulsed from that end and drawn toward the other end of the cylinder? If so, how do the springs fit in?
  8. May 7, 2004 #7
    Let me try to start from the end of your contraption. Induced current always comes from changing magnetic field around the coil. The current induced is a direct current (DC). Your setup seems like an alternating current (AC) because of the up-down motion of the charge sphere. So if the motion is symmetrical, the current induced change direction in equal interval. The result is that the motion of these opposite currents cancel each other the net effect is no current can be detected in the coil.
  9. May 8, 2004 #8
    Well firstly I am not sure if it is indeed AC.If it is could it not be rectified?
  10. May 8, 2004 #9
    If I remember my physics correctly, rectification is possibly the only way that can make the current of your device flows in one direction. The way it is, your device is just "alternating" DCs. There is also a possibility that the charge will eventually slow down its up down motion and stays floating motionless. The energy could also be transferred into the spin of the charge sphere after its creation.
  11. May 11, 2004 #10
    Please let us concentrate on the possibility that the charge will eventually slow down its up down motion and stays floating motionless.Could you explain exactly how the charge distribution would happen,as I do not have a full knowledge on charge distribution.
  12. May 11, 2004 #11
    A complete analysis can take a while. But we can start with the possible forces involved. There is the Hooke force of the spring, the coulomb force of the charge, and gravity force for the downward motion of the charge.

    If the ends of the cylinder is charged and can be keep at a constant state of charge (constant electric field), then the Hooke force is not necessary. It's an overkill.

    With just the electric force and the gravity force, this is just similar to Millikan's oil drop experiment.
  13. May 11, 2004 #12
    Millikan's drops are single polarity drops (+ or -). Your sphere is dipolar (+ and -). Assuming that you can maintain the dipolarity of the sphere, the electric force will induced a torgue in such a way that it can apply a spin to the sphere.
  14. May 11, 2004 #13
    Quickly jumping to conclusion, your device, if it works, solved a long standing problem in plasma physics. The key is to keep the sphere dipolar. If there are more than one sphere, the velocity distribution can become extremely complicated and very interesting! There might exist a global dynamic equilibrium! End result is more electricity than anyone can shake a stick with.
  15. May 11, 2004 #14


    User Avatar

    Staff: Mentor

    That's not a theory, its a device. A theory would be the explanation for how it does what it does (make damn good milkshakes due to a unique mixer for example...).

    It sounds like you think there is an oscillation going on in there and are wondering why it wouldn't oscillate forever. The answer is simple: damping.
    Last edited: May 11, 2004
  16. May 11, 2004 #15
    Can you please explain more fully?I am assuming there's oil in there,as well.It will prevent corrosion of the spring,if that's what you're wondering.It's lift force or upthrust of floatation will hopefully counter gravity.Also,I was thiking,to reduce energy loss via spinning,I thought maybe we could make it instead of a sphere,a cuboid.With two surfaces which are much larger than the rest and hence most pressure is on those 2 surfaces,also only those 2 surfaces will touch the charged springs.
  17. May 12, 2004 #16
    If the oil is replaced by a vacuum chamber (no corrosion) and take away the springs for now and maybe reconfigure the cynlinder which will change the shape of the electric field then you have a simple room temperature plasma machine for generating electricity.
  18. May 12, 2004 #17
    I do not understand.Oil will not corrode the springs,as they will be made from a conducting metal.Also,why remove them?
    And thirdly,as I said before,the shape I think would be best is cuboid.Instead of a sphere,we can have a cuboid.(read my last post!)
    Antonio,your idea will require energy to sustain the vacuum environment.Why do you call it 'plasma'?
  19. May 12, 2004 #18
    Springs are based on mechanical forces. Pound per pound, mechanical forces are far less efficient than electrical forces. In the progress of modern technology, all mechanical devices are being constantly replaced by electromechanical devices. For example, the steam locomotive train is replaced by modern maglev train. The maglev train might cost more to maintain but it is faster, serving its purpose of moving working people around the metropolis.

    In all devices, they always require energy input for energy output. it's just the form of energy that is changed, say from potential to kinetic, from rest to motion, vice versa.

    Plasma (laser fusion, Tokomak, PLT and others around the world) is one of the current frontiers of research in producing limitless electricity.
  20. May 12, 2004 #19
    There are several mechanisms for energy loss in that device: oil-sphere friction, sphere-spring collisions, and resistance of coil (maybe some others that I haven't noticed). All these convert "useful" energy into heat. This means that the sphere would move around an equilibrium while loosing energy, until it has lost all energy, at which point it would stop at the equilibrium. You might be able to extract some work from the device, but it is finite.

    Even if you assume ideal conditions, and the above energy loss mechanism are neutralized, you would acheive unity at most. The moment you try to extrat work from the device, the sphere would start lossing energy to produce the work, and would eventually stop at the equilibrium.
    Last edited: May 12, 2004
  21. May 12, 2004 #20
    OK.If we assume that:
    1.the springs are perfectly elastic
    2.There is no sphere-oil friction
    3.No coil resistance

    Why would it not work.(I did not really understand that last paragraph).
    @Antonio: you mean plasma things are perpetual motion??
  22. May 12, 2004 #21
    Plasma are ionized gas. As a whole, it is neutral. Because it is made of equal number of positive and negative charged particles. The dynamics of this ionized gas is extremely complicated.

    In order to achieve fusion of hydrogen nuclei, high temperature and high density must be satisfied simultaneously. But with your dipolar spheres, what I am thinking, the dynamics can become less complicated.
  23. May 12, 2004 #22
    Thanks for that. But still...
    If we assume that:
    1.the springs are perfectly elastic
    2.There is no sphere-oil friction
    3.No coil resistance
    Why would it not work.
  24. May 12, 2004 #23
    Assuming ideal conditions:
    Let's put the coil aside for a moment. The only forces that are acting there are electromagnetic and gravitational (the oil would not have any effect if there is no friction between the oil and the sphere). Both these types of forces are conservative. So if you assume a cyclic motion, you would not be gaing any energy from the movement (all the energy you gain going one way is lost going the other way, and vice versa). And since you're not gaining any energy, you don't have any to spare energy to convert into work.

    Now put the coil back. Making the electrons in the coil move requires work input. But we just said you can't produce any work. Hope this makes this a bit clearer.
  25. May 12, 2004 #24
    In theory (total idealization), your device will work, but in practice, it is not sustainable. It might work for a fraction of a second but not in a second. The working of your device might be analogous to swimming upstream. It is possible but difficult. Sooner or later you get overwhelm by the natural tendency of what nature want to do. Nature will always minimize the expenditure of time and energy. That's is why the shape of raindrops is a pancake and not a tear or a sphere.
    Last edited: May 12, 2004
  26. May 12, 2004 #25
    Well it seems then that there are more mechanisms for energy loss.Could you please try and list them *all* or as many as you know here?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook