Superconductivity

[Kryten]

A book laying on the table is levitating. I see....

It is. It's not in real physical contact, it's repulsed by electrostatic forces.

[Ralathon]

Well the problem is it is not only levitating, there are times at this experiment where the carriage is also holded by the track when it goes upside down. In both cases a force is holding it in place countering the gravitational pull. And you want to tell me now that there is no energy needed for that and also that this experiment is not violating any rules od nature? *Pahh*

You will need to do better than that if you want to explain it.

Force does not mean energy. I am currently experiencing a force pulling me towards the center of the earth. But I am not gaining energy because my distance from the center of the earth stays the same. Same thing with the magnets there, they experience a force that keeps it to the rails, but it is not moving relative to the rails. So it doesn't need any energy to do this.

Energy is force acting over a distance. It's why we can't harness the water pressure behind a dam without letting the water flow. Or how batteries can hold charge. It's a pretty basic bit of physics.

A book laying on the table is levitating. I see....

For all intents and purposes it is. You're just attacking a strawman while ignoring the whole point of his argument.

[rtxoff]

A current flowing is generating a magnetic field. The same magnetic field is exists in a permanent magnet without the flow of current.

In one case there is energy involved in the other not? What is this black magic?

[Kryten]

In one case there is energy involved in the other not? What is this black magic?

if the current is in a superconductor, you can have the first case with no energy being used. Any field, whether electrostatic, magnetic or gravitational, does not fundamentally use or produce any energy.

[Jovus]

Ferromagnets are magical. Explanations using classical electrodynamics don't work.

[rtxoff]

if the current is in a superconductor, you can have the first case with no energy being used. Any field, whether electrostatic, magnetic or gravitational, does not fundamentally use or produce any energy.

Hmm let me check on that.

Electrostatic fields, i can't think of any case where one would create such a field without energy.

Magnetic fields exist in nature in form of permanent magnets without some energy input. Check on that one. However there might be energy involved we don't see? Idk.

Gravitational field. Exists where there is mass. Mass as we all know is the same as energy or maybe not?

Producing energy? Are you kidding me. Every school kid knows that energy can't be produced only converted.

BTW converting energy. A moving magnetic field through a conductor results in an electric current. Electric currents are energy. Halleluja, we invented the wheel.

[Ralathon]

A current flowing is generating a magnetic field. The same magnetic field is exists in a permanent magnet without the flow of current.

In one case there is energy involved in the other not? What is this black magic?

If you generate a magnetic field with a coil and current you don't have to pump in energy to sustain the field. All you need is to compensate for the resistance of the wire.

Magnetic fields work a lot like flywheels. It takes a bunch of energy to get one started, but once it is going you need minimal/no energy to keep it going. They also don't like sudden changes, that's why we use coils for things like spark plugs.

[cpast]

Well the problem is it is not only levitating, there are times at this experiment where the carriage is also holded by the track when it goes upside down. In both cases a force is holding it in place countering the gravitational pull. And you want to tell me now that there is no energy needed for that and also that this experiment is not violating any rules od nature? *Pahh*

You will need to do better than that if you want to explain it.

Correct. No work is being done holding something in place. Therefore, no energy is expended. Your confusion seems to be with the common definition of "energy" (and "work"), according to which it takes energy to continually apply a force. This is not the case; you do no work on an object unless you apply a force in a direction over a distance in that same direction. When the track goes up, work is being done on the object; however, I'd expect the energy there to come from the kinetic energy of the object (i.e. separation from track changes -> induced current strength changes and object slows -> unbalanced force -> acceleration upwards, less forward speed). However, if you think energy is needed for a force to hold something in place against gravity, you misunderstand the concepts of work and energy.

[rtxoff]

If you generate a magnetic field with a coil and current you don't have to pump in energy to sustain the field. All you need is to compensate for the resistance of the wire.

Magnetic fields work a lot like flywheels. It takes a bunch of energy to get one started, but once it is going you need minimal/no energy to keep it going. They also don't like sudden changes, that's why we use coils for things like spark plugs.

Ahh now we are getting closer. Superconductors don't have any resistance right?

So they have no losses, if we use your flywheel analogy it is something very similiar to a flywheel perpetuum mobile or not?

[pellinor]

Ahh now we are getting closer. Superconductors don't have any resistance right?

So they have no losses, if we use your flywheel analogy it is something very similiar to a flywheel perpetuum mobile or not?

Exactly. And physics does not have any problems with a perpetuum mobile as long as it respects conservation of energy.

[Ralathon]

Ahh now we are getting closer. Superconductors don't have any resistance right?

So they have no losses, if we use your flywheel analogy it is something very similiar to a flywheel perpetuum mobile or not?

If you mean perpetuum mobile as in "It will never stop" then yea, you're right. If you take a shorted superconducting coil and make it carry a current it will produce a magnetic field and it will hold that magnetic field until eternity. Or until the nitrogen boils off and the coil stops being superconducting.

If you mean perpetuum mobile as in "Free energy from nothing" then you are most definitely wrong. Energy comes from changes. Changes in fields, changes in potentials etc. If you have a superconducting coil carrying a constant current nothing is changing in the whole system, so you can't get energy out of it. There is some energy stored in the magnetic field of course, and you can get it out by breaking the circuit. But that's no more magical than a battery.

[cpast]

BTW converting energy. A moving magnetic field through a conductor results in an electric current. Electric currents are energy. Halleluja, we invented the wheel.

Energy obtained by doing this does not come from the magnetic field; it manifests itself in the fact that moving a magnetic field-producing object through a conductor, or moving a conductor through a magnetic field, takes energy. If you're doing this by hand, you have to do work to move a magnet through a coil of wires. The more energy being bled off by the circuit, the harder it is to move the magnet through a coil. Many railroad locomotives have a brake that literally consists of connecting the traction motor to a grid of resistors, because driving a high-resistance circuit with a generator slows down that generator (in this case, kinetic energy becomes electrical energy becomes heat in the resistor).

[rtxoff]

If you mean perpetuum mobile as in "It will never stop" then yea, you're right. If you take a shorted superconducting coil and make it carry a current it will produce a magnetic field and it will hold that magnetic field until eternity. Or until the nitrogen boils off and the coil stops being superconducting.

If you mean perpetuum mobile as in "Free energy from nothing" then you are most definitely wrong. Energy comes from changes. Changes in fields, changes in potentials etc. If you have a superconducting coil carrying a constant current nothing is changing in the whole system, so you can't get energy out of it. There is some energy stored in the magnetic field of course, and you can get it out by breaking the circuit. But that's no more magical than a battery.

Energy obtained by doing this does not come from the magnetic field; it manifests itself in the fact that moving a magnetic field-producing object through a conductor, or moving a conductor through a magnetic field, takes energy. If you're doing this by hand, you have to do work to move a magnet through a coil of wires. The more energy being bled off by the circuit, the harder it is to move the magnet through a coil. Many railroad locomotives have a brake that literally consists of connecting the traction motor to a grid of resistors, because driving a high-resistance circuit with a generator slows down that generator (in this case, kinetic energy becomes electrical energy becomes heat in the resistor).

Well i am very well aware of this. Still someone said a few posts ago there is no energy involved in the experiment i posted. Sure there is energy involved and not only fields.

There is an initial energy input to build up the field (The moment the guy puts the carriage on the track) and that field is preserved as long as the superconductor is cooled down sufficiently.

So that carriage is loaded with energy in the form of an magnetic field which never looses its strength.

Everybody can preach some fundamental laws of physics here but only a few take the time to explain and discuss them on actual experiments.

[Bill Phil]

What is this thread about? I'm kind of lost...

[Rakaydos]

What is this thread about? I'm kind of lost...

Magnets... how do they work?

[Bill Phil]

Domains.

That's how.

[GoSlash27]

A current flowing is generating a magnetic field. The same magnetic field is exists in a permanent magnet without the flow of current.

In one case there is energy involved in the other not? What is this black magic?

There is energy converted from one form to another, but because the superconductor has no electrical resistance none of it is lost as heat.

The motion of magnetic flux lines in the superconductor generates an electric current in the superconductor. The current in the superconductor generates a magnetic field opposed to the initial flux movement. This creates a force that cancels the initial flux motion.

The only energy lost is in the form of heat due to aerodynamic drag, but the velocities are so tiny that the losses are almost imperceptibly small.

In the case of a permanent magnet, there is no energy so long as the flux is not moving. There is only force.

In the case of an electromagnet, there is energy lost in the form of heat due to the current flow, but just as in a permanent magnet there is no "energy" in the magnetism that results, merely force.

You need force and motion to create energy.

I hope I'm not confusing you further...

Best,

-Slashy

[mfkdso]

You Sir, are by far are the most helpful answer I've gotten. Thanks a bunch. Honestly I'm only 14 with only bare bones knowledge in physics. It's pretty cool to be in a community of people, where I can just ask a question, and have a whole host of nice people with helpful answers. Thank you Ralathon. And thank you everyone else who have, or will reply. Teach on.

[rtxoff]

*snip*...You need force and motion to create energy.

I hope I'm not confusing you further...

Best,

-Slashy

Well sorry but that's not exactly right. You can't create energy. You can convert energy forms into other energy forms. In that particular case involving moving magnetic fields through conductors you are converting kinetic energy into electric energy.

[N_las]

Well sorry but that's not exactly right. You can't create energy. You can convert energy forms into other energy forms. In that particular case involving moving magnetic fields through conductors you are converting kinetic energy into electric energy.

Yes, I am sure GoSlash27 didn't meant "creating" in the literal sense. What he means is, that you don't need any energy to hold a system in Place against a constant force. Like my example with the book on the table. The book is constantly resisting against the force of gravity (it is "levitating", with the help of the table). But it doesn't need energy for that. You may have needed energy to put the book on the table, but once there it can remain there indefinetly.

The same is true for the reverse. To convert your muscle energy into electrical energy, you have to work against a force over a motion.

Your original question was something like: "Were does the energy come from to hold the superconductor in levitation?" It needs energy to put it onto the rail. A part of that energy is coverted into a current in the superconducter. But once on the track, you don't need an energy supply to keep it levitating (exactly like the book, that doesn't need an energy supply to keep "not falling").

[GoSlash27]

Well sorry but that's not exactly right. You can't create energy. You can convert energy forms into other energy forms. In that particular case involving moving magnetic fields through conductors you are converting kinetic energy into electric energy.

Yeah, imprecise use of terms on my part. "Create" is incorrect and not what I meant.

My point is that "force" is not "energy". This seems to be at the heart of your misunderstanding.

Best,

-Slashy

[rtxoff]

My point is that "force" is not "energy". This seems to be at the heart of your misunderstanding.

Best,

-Slashy

You are right, force it not energy however you need energy to build up a force. So there is only a thin line between them.

[Ralathon]

You are right, force it not energy however you need energy to build up a force. So there is only a thin line between them.

Energy is force over a distance yea. As we've been telling you all along. So the answer for your original question:

Edit: A magnetic field inducing current in a superconductor which creates it's own magnetic field which locks onto the moebius strip.

So any smart people here tell me where the energy is coming from for that

Is that you use some initial mechanical energy to lock the superconductor (this gets dumped into the magnetic field of the superconductor). After that it is not moving relative to the field so it no longer requires additional energy to stay afloat.

[-Velocity-]

You seem to be willing to have an open mind if someone just reasonably explains stuff, so I'll have a go-

You are right, force it not energy however you need energy to build up a force. So there is only a thin line between them.

Energy = work = force*distance. A force can be manifest but do no work and create/require no energy, as long as the object its acting on does not move. This is why it takes no input energy to continuously magnetically levitate something. In fact, you don't even need superconductors to demonstrate magnetic levitation. Materials that are strongly diamagnetic will generate an opposing magnetic field to an externally applied one, and some are strong enough to levitate over rare-earth magnets. This occurs at room temperature.

And yes, an object resting on a table is, in a very real way, being levitated electrostatically over the ground by the table. Remember how negatively charged electrons are located on the periphery of the atom while the positively charged protons are in the center? Remember how like charges repel? Well, when two surfaces come into "contact" with each other, what's really happening is that the surfaces get so close that the relative distance between the outermost electrons in the electron clouds in the surfaces of the objects is much less than the relative distance between the nuclei of the outermost atoms. Because the outermost electrons of the two surfaces are much closer than the outermost protons, a net repulsive force results, repelling the two surfaces from each other and giving the "illusion" of solid matter.

Atoms very much have local, un-neutralized electric fields, and these fields are not uniform either due to electron orbitals, and from this arises all of chemistry.

Oh, and by the way, in something mind blowing that even most electrical engineers don't know about (even those that study EM field theory!), is the connection between electromagnetics and Special Relativity. Magnetic fields arise from electric fields through length contraction of moving charges, and so, in very real way, are nothing but electric fields themselves. All of electromagnetics can be derived from Coulomb's law and Special Relativity. In fact, I think I read somewhere that one of the things that inspired Einstein was his conviction, eventually proven correct, that electric fields and magnetic fields were in fact the same phenomenon.

BTW I am an electrical engineer myself so I know what I'm talking about.

Edited February 4, 2015 by |Velocity|

[rtxoff]

You seem to be willing to have an open mind if someone just reasonably explains stuff, so I'll have a go-

Energy = work ... *snip*

Just no. Energy isn't work. Work can be done by converting one form of energy into another however.