Give your Opinion !

[Commander]

Two Circular Iron Plates and another Heavy Circular Weight are stacked one above other. In the pattern below.

 

 

The whole thing A, B & C touching each other is weighed together and weighs X.

 

A & B are then magnetised and the arrangement put up again A, B & C once again in contact with each other. This arrangement weighs Y. Obviously A & B are stacked with compatible Polarity.

 

Then B is inverted and the magnetic force is such that B& C are in contact but they float above A without physical contact [just like those trains these days]. This arrangement weighs Z.

 

The Question is :

 

Will X be equal to Y ?

 

Will Y be equal to Z ?

 

If Z = Y but > X , then will Y-X be equal to the Energy pushed into the Stack and the Energy added E will be equal to [Y-X] * c² where c is Speed of Light ?

[Fuzzwood]

X = Y = Z. Attraction or repulsion doesn't change the mass of the system and weight is defined as F_z = m*g

[EdEarl]

Fuzzwood is correct because magnetism and gravity are different forces.

[Strange]

Does a magnetixed object have more energy than an unmagnetized one? (I don't know the anser to that.) If it does, then that would make a minuscule difference to the weight. But the arrangement of the disks would not.

[xyzt]

Does a magnetixed object have more energy than an unmagnetized one? (I don't know the anser to that.) If it does, then that would make a minuscule difference to the weight.

The total energy of the unmagnetized body is [math]E_0=m_0c^2[/math].

A manetized body of same mass, [math]m_0[/math] has the total energy [math]E_1=\sqrt{(m_0c^2)^2+(pc)^2}[/math], where [math]p[/math] is the resultant momentum due to the spin of the elementary magnets making up the body. So, yes, [math]E_1>E_0[/math].

 

 

 

But the arrangement of the disks would not.

 

This is a tricky one: the answer is a function of the magnets orientation. If the momenta add up, then the total energy increases, if the momenta cancel out, then the answer is no. This is exactly like the question about the total energy of two fascicles of photons. Total energy of a system in relativity is a tricky issue.

Edited December 17, 2014 by xyzt

[imatfaal]

The total energy of the unmagnetized body is [math]E_0=m_0c^2[/math].

A manetized body of same mass, [math]m_0[/math] has the total energy [math]E_1=\sqrt{(m_0c^2)^2+(pc)^2}[/math], where [math]p[/math] is the resultant momentum due to the spin of the elementary magnets making up the body. So, yes, [math]E_1>E_0[/math].

 

So the spins being all over the place in an un-magnetized lump of iron would cancel out to give no net momentum - but when a decent number aligned there is a net momentum and thus an increase. Is that along the right lines?

 

And this is a linear momentum? or angular? Angular would make sense as they are spins aligned but I have never seen it included in that formula as you have done. Linear is hard to envisage but fits in the formula

[xyzt]

 

So the spins being all over the place in an un-magnetized lump of iron would cancel out to give no net momentum - but when a decent number aligned there is a net momentum and thus an increase. Is that along the right lines?

 

 

Correct.

 

 

 

And this is a linear momentum? or angular? Angular would make sense as they are spins aligned but I have never seen it included in that formula as you have done. Linear is hard to envisage but fits in the formula

 

Angular. The formula is about resultant momentum, in this case , it happens to be angular.

[Sensei]

Actually I have made such experiment in reality.

 

Put magnets (Neodymium) inside of test tube (so they couldn't rotate), NS-SN (magnets levitated on another without touching anything).

 

And placed everything on weighting scale.

 

I will later make photo, if I find some unbroken test tube..

Edited December 17, 2014 by Sensei

[MigL]

But if you consider each magnetic domain, xyzt, then each has a particular energy.

They each have a particular energy whether aligned or not.

So even though the spins of the individual domains may cancel, there is no negative energy.

The total energy would still be the sum over all domains, and therefore equal for magnetized or non magnetized.

 

Or am I missing something ?

[xyzt]

But if you consider each magnetic domain, xyzt, then each has a particular energy.

They each have a particular energy whether aligned or not.

So even though the spins of the individual domains may cancel, there is no negative energy.

The total energy would still be the sum over all domains, and therefore equal for magnetized or non magnetized.

 

Or am I missing something ?

Yes, you are missing the fact that momenta, by virtue of being vectors, can subtract (if they have opposite senses). This is why I pointed out that the case is identical to the one of two fascicles of photons.

So, in the case of the two magnets that cancel each other's field, the energy is truly

[math](m_{01}+m_{02})c^2[/math] and not [math]\sqrt{(m_{01}c^2)^2+(+pc)^2}+\sqrt{(m_{02}c^2)^2+(-pc)^2}[/math] as one would think.

Edited December 19, 2014 by xyzt

[Acme]

Let's not overthink this. The stack weighs the same even with levitation. Every action has an opposite & equal reaction don't ya know.

.

PS Without some mechanism to hold the floating disk in place, it won't stay in place. A clear containing cylinder would do nicely, which of course must be in place for all weighings.

[Commander]

Let's not overthink this. The stack weighs the same even with levitation. Every action has an opposite & equal reaction don't ya know.

.

PS Without some mechanism to hold the floating disk in place, it won't stay in place. A clear containing cylinder would do nicely, which of course must be in place for all weighings.

 

I agree that just reversing the direction of magnetism itself shouldn't result in change of weight.

 

But I think charging any component of the structure with Electricity, Magnetism or Heat must have an effect on the weight albeit minute !

[Acme]

I agree that just reversing the direction of magnetism itself shouldn't result in change of weight.

 

But I think charging any component of the structure with Electricity, Magnetism or Heat must have an effect on the weight albeit minute !

Fortunately you can test your thinking with experiments. Sensei said he has done the experiment with magnets and will do it again and make photographs and post them. By no means let this prevent you from performing your own experiments as reproducibility is a keynote of science.

[Commander]

Fortunately you can test your thinking with experiments. Sensei said he has done the experiment with magnets and will do it again and make photographs and post them. By no means let this prevent you from performing your own experiments as reproducibility is a keynote of science.

 

Acme : Thanks !

[xyzt]

 

I agree that just reversing the direction of magnetism itself shouldn't result in change of weight.

Doesn't matter what you agree, I have just shown that the resultant momentum changes the mass of a system. Even more, the stress-energy-MOMENTUM tensor is what determines the gravitational effects, as illustrated by the Einstein Field Equations.

Edited December 19, 2014 by xyzt

[Strange]

Fortunately you can test your thinking with experiments.

 

Although I imagine the effect described by xyzt would result in an immeasurably small change in mass.

[Fuzzwood]

Well, imo there is another effect. The levitated magnet is just a fraction more distanced from the gravity well than the magnet below it. Since gravity scales as 1 over r², the levitated magnet will experience less gravitational force. On the other hand, there is a lump of metal with a certain mass directly in its path, which will add a bit to the attractive force.

[Acme]

 

Fortunately you can test your thinking with experiments.

Although I imagine the effect described by xyzt would result in an immeasurably small change in mass.

 

Roger. Took me a momenta there to differentiate between Commander's XYZ and xyzt the person. So while the difference may be immeasurable by a scale, it is calculable using xyzt's formula if we give specific values to the variables?

[xyzt]

 

Although I imagine the effect described by xyzt would result in an immeasurably small change in mass.

Correct.

[Vexen]

I don't understand anything here. Can someone explain in a less technical way?

Edited December 19, 2014 by Vexen

[xyzt]

Roger. Took me a momenta there to differentiate between Commander's XYZ and xyzt the person. So while the difference may be immeasurable by a scale, it is calculable using xyzt's formula if we give specific values to the variables?

Yes.

[Strange]

I don't understand anything here. Can someone explain in a less technical way?

 

Mass is related to energy through the well-known equation E=MC². However, it is less well-known that the full form of this equation includes momentum. Magnetism is related to the orbital angular momentum of (unpaired) electrons in the atoms of the material.

 

When these orbital spins are randomly aligned the material is unmagnetised (because they all cancel out) and also the net angular momentum is zero (because they all cancel out). But when you align them, the material becomes magnetized and the total angular momentum increases. This increases the mass of the material.

 

(I mainly wrote this to see if I have got it right. )

Edited December 19, 2014 by Strange

[xyzt]

 

Mass is related to energy through the well-known equation E=MC². However, it is less well-known that the full form of this equation includes momentum. Magnetism is related to the orbital angular momentum of (unpaired) electrons in the atoms of the material.

 

When these orbital spins are randomly aligned the material is unmagnetised (because they all cancel out) and also the net angular momentum is zero (because they all cancel out). But when you align them, the material becomes magnetized and the total angular momentum increases. This increases the mass of the material.

 

(I mainly wrote this to see if I have got it right. )

Correction, mass (inertial) is an invariant. What increases is the total energy, not the mass:

 

[math](m_0c^2)^2=E^2-(pc)^2[/math]

[EdEarl]

I don't understand anything here. Can someone explain in a less technical way?

There are two central ideas in this thread, one concerning gravity and magnetism, and the other about energy and mass. Do you not understand either one or both?

 

If your question concerns the energy-mass idea, it is related to E=mc^2 (Einstein), which relates mass and energy. Anytime a mass gains energy, i.e., warming or being magnetized it gains mass. To truly understand you need to get into the math and physics. A good place to start is https://www.khanacademy.org/.

[Strange]

Correction, mass (inertial) is an invariant. What increases is the total energy, not the mass:

 

Maybe it would have been better (for the lay reader) to use something like "effective mass" or "total mass" to make the distinction a little bit clear.