Hami Hashmi

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What if the saturation of mu-metal was 0? Would it enhance the outside field then?

And what stops the ferromagnetic layer of the antimagnet producing a magnetic field?

Thanks.

Ok fine but for the sub-microsecond that they are together what will be the spin then?

Ok thanks. So the resulting particle will have a spin of 1/2?

30 minutes ago, swansont said:

No. Just the spin projection (spin up vs. spin down)

There is only one way for the quarks to combine and have it be a proton. There are two up quarks. They have to be anti-aligned in the ground state because of the Pauli exclusion principle 

Ok but then is it possible to change the magnitude of the spin of a electron and up quark (i know this would not be stable but for the limited time that it is would it be possible?)

Because the proton is not an elementary particle so I was wondering if it was possible to change the magnitude of the spin.

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3 hours ago, Strange said:

Why would it enhance the field? As it says, it would block the magnetic field. Almost the opposite of enhancing it. 

Bu the way, that website is not in general a reliable source of information. Although, in this case they have just copied a press release.

original article here, for anyone interested: https://arxiv.org/abs/1107.1647

No what i meant is that if there was a hollow box made of that material and there was a magnet placed inside of the box and a magnetic field generated outside, would the box enhance the outside magnetic field in any way? Because I heard that magnetic shields tend to do that.

Would a box made of this enhance an external magnetic field?

https://peswiki.com/powerpedia:antimagnet

Would this work?

https://peswiki.com/powerpedia:antimagnet

.

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Is there any known material or process that will not enhance the outside field but block the field inside?

Alright thanks for your help! 

1 hour ago, swansont said:

In this case yes; the original field was uniform. Now the flux lines preferentially go through the long dimension of the shields instead of passing through inside or outside.

The electromagnet or transformer core is not a magnet itself. It concentrates the flux lines from the windings so that the north/south pole is stronger. Flux lines that might have left the windings further away are now in the core. In a shield, flux lines that might have entered the interior are instead in the shield walls.

 

edit:

https://quickfield.com/advanced/mu-metal_shielding.htm

This is a different geometry (transverse to the cylinder instead of aligned with it) but it shows field lines outside but nearby the shield bending toward it, for the lines entering, and bending away when leaving. The field inside is small.

Thanks for the explanation! So basically in an external field a shield will nullify the field inside it but enhance it outside around the north and south poles?

32 minutes ago, swansont said:

That's going to generate a magnetic field, which will be enhanced in the shielding material. Outside, not really. Depending on the shapes and sizes involved, you might modify the dipole pattern emanating from the box. 

You use a core in a transformer to ensure a strong field is in both the primary and the secondary. It doesn't enhance anything outside.

 

Here's what a the fields looks like when a cylindrical set of shields is placed in a uniform vertical field. The intensity follows the color spectrum (red is the most intense field, blue is least. There is a small field present in the innermost cylinder)

IIRC the exterior field would be depicted as orange

Ok thanks.

So outside the box and above the box the field would be strongest. Does the box enhance the field in the red areas?

So the main difference between a soft iron electromagnet and a soft iron shielding box is that the box is hollow and the magnet is solid? Is that what causes the difference between them?

16 hours ago, swansont said:

No. The field will tend to be inside the iron.

Ok but if the had the same scenario but with wires wrapped around the box and a current passed through them and no external magnetic field, would the magnetic field then be enhanced outside the box?

3 minutes ago, swansont said:

Enhance it where? The field will tend to be in the iron box. But both magnets will be attracted to the shield

Enhance it outside the box.

3 hours ago, swansont said:

Field lines "prefer" to be in the high mu region but it's not attraction, per se. IIRC a bar of such material put in a uniform field would result in something that looks like a dipole. 

The domains align when there is an external field.

The same thing is going on. A shield doesn't absorb the field - it doesn't disappear. The flux lines go into the shield, rather than through it. They exit the shield as well. The interior - the shielded region - has a substantially smaller field.

Yeah I understand that it doesn't completely absorb the field.

But what if there was a soft iron box with a magnetic material inside, and a magnetic field was produced outside of the box, would the soft iron box enhance the magnetic field or diminish it? 

There is a description here: https://www.mumetal.com/about_mumetal.php

6 hours ago, John Cuthber said:

Nope.

Soft iron is used for shielding. It's not quite as good (because it has a lower permeability), but it's cheap.

 

Ok but in an electromagnet the wire wrapped around the core (which is mostly soft iron) generates a magnetic field when a current is passed through it, which then is amplified by the core. But in a shield, soft iron absorbs the magnetic field instead of enhancing it. So why is that?

Just found a relevant thread 

So the way I see it is that mu-metal has a low saturation which is why it is good for shielding. But how do mu-metal's atoms differ from soft iron's as to make it have low saturation?

2 hours ago, swansont said:

On an atomic level the difference is that mu metal has atoms other than iron in it.

"soft iron enhances a magnetic field and mu-metal absorbs it"

No. You can't "absorb" a magnetic field. Soft iron and mu metal do basically the same thing to magnetic fields.

Mu-metal is used in shielding applications while soft iron is not. They both have a high mu and low solubility so what makes mu-metal different so that it can be used in shielding applications?

Ok I see.

4 hours ago, studiot said:

Strange, +1 for qualitative answers, in particular referring to the electonand the nucleus thread.

We could, of course, put some numbers to this, but avoiding the dreaded division by zero.

The De Broglie wavelength of an electron of mass m moving at velocity v is h/mv.

For a given (small ) region of space of size s, this wavelength must be smaller than s to say that the elctron is definitely within that region s.

For instance the nuclear radius is 1.5 x 10^-14 metres.

So to say that the electron is within this space means puts a lower limt on mv.

The value of h is 6.6 x 10^-34 joule-seconds and the mass of the electron is 9 x 10^-31 kilogrammes.

 

I will leave it as an exercise for hami to insert into the relationships and find the required velocities for any given small space s.

Prepared to be suprised.

I understand about the Heisenberg uncertainty principle but if the particles in a black hole can bind together into a singularity then what about two point particles? 

https://physics.stackexchange.com/questions/193954/do-black-holes-violate-the-uncertainty-principle

2 minutes ago, Strange said:

They are a consequence of "naively" extrapolating general relativity to an area where we are fairly sure it doesn't work. It is almost certain that a quantum theory of gravity will cause gravitational singularities (in both black holes and the Big Bang) to disappear.

Oh ok. But they have not actually been eliminated right?