/sci/ - Science & Math

[Anonymous No.10783860]

>earth magnetic field is generated by an electric current in the outer core
>outer core would need to be inside an alternating magnetic field already in order to generate a current that could generate a magnetic field

Why does the "dynamo theory" sound like complete hogwash?

[Anonymous No.10783915]

>>10783860
I'm so glad /sci/ exists so people like OP have someplace to post. Just think how much better the rest of the internet and world is with so many trolls and schizophrenics who would otherwise be bothering normal people, instead being here, making troll threads and troll posts and accusing each other of being shills. Think of all the people who didn't have to endure those people today. It's beautiful.

[Anonymous No.10784079]

>>10783860
>outer core would need to be inside an alternating magnetic field

careful with this quote, a magnetic field its always generated with a DC current. this has to be well understood because a changing current (AC) has the capacity to "erase" a magnet, literally this is how a demagnetizer works (using an electromagnet BUT applying an AC current will "erase" the remanent magnetism of iron objects, this is a very interesting phenomena and the explanation is related to the magnetic hysterisis characteristic of some metals)

if we belive or trust that maxwell equations are correct and universal, every magnetic field has an electric field associated with it , if we are observing or detecting a magnetic field this would mean that a current (a DC CURRENT or a current that could have "some change" but it has to maintain an overall DC characteristic) existed in the past that magnetized an object or an electric current that exist right now is creating that magnetic field , those are the two posibilities there can not be a spontaneous magnetic field that just happens to be there or just happen to appear out of no-where without an electric current associated with it.

[Anonymous No.10784633]

>>10784079
>a magnetic field its always generated with a DC current
Make a closed copper coil and see how much current is generated by it alone

Hint: it's none

You only get current when a magnetic field is moving through/around it

I just don't buy the "dynamo theory", you know what I mean?

[Anonymous No.10784653]

>>10784633
All the dynamo theory needs is: an electrically conducting fluid, convective currents, and a small seed magnetic field (this last one could just be a tiny, random fluctuation which is bound to occur in a hot, giant circulating vat of iron).

From there, the convection passing through the magnetic field will induce a stronger field, in a feedback process capping out at a point dependent on the nature of the convective flow and Coriolis effect. This is understood through magnetohydrodynamic simulations. It's fair to say the exact details of each process are still being fleshed out, but the groundwork theory and simulations are solid.

[Anonymous No.10784662]

>>10784079
>a magnetic field its always generated with a DC current
But in order to generate current you need an alternating magnetic field, otherwise you don't get any current at all (if that was the case you could build a "free energy device" that could generate current from being inside the earth's magnetic field alone) . Try it in the scope.

[Anonymous No.10784674]

>>10784653
>an electrically conducting fluid
Yes
>convective currents
I suppose so, if it's a liquid
>this last one could just be a tiny, random fluctuation which is bound to occur in a hot, giant circulating vat of iron
This would happen only in a boundary layer, if it's possible at all

[Anonymous No.10784675]

>>10783860
But the magnetic field can exist without the electric current. Think of a regular magnet. So I thought the core was just a giant magnet.

[Anonymous No.10784680]

>>10784675
>But the magnetic field can exist without the electric current. Think of a regular magnet. So I thought the core was just a giant magnet
The earth core can't be a permanent magnet if it is indeed a ball of iron or any other metal at 6000ºC

[xxXSuiseisekiXxx No.10784717]

>>10784680
I thought it was a slush magnet. Eddies in the magma causing polarization. Like kinda how magnetic breaking works.

[Anonymous No.10784727]

>>10784633
>>10784662
i'm sorry that phrase was in the context of a magnetized object or if we consider the magnetic field of the earth as a magnet thats why I also explained that an AC field actually can erase a magnetized object

>>10784662
>But in order to generate current you need an alternating magnetic field, otherwise you don't get any current at all

what you need if you start from a current is a CHARGE IN MOTION and if you start from a magnetic field you need to move the magnetic field the problem we are having here I think it comes from the practicality aspect of a machine that will generate a pure DC (without interruption or without the DC collector) by moving a magnet only in one direction and continously without internally reversing polarity, then like I said before an electromagnet will maintain his polarity only if you apply DC but if you apply AC it will continously reverse polarity according to the frequency of the AC.

[Anonymous No.10784735]

>>10784674
The Sun's magnetic field is sufficient to serve as a seed for Earth. The Sun is mostly plasma and will naturally have spontaneous electric currents forming all the time for its own seed.

[Anonymous No.10784759]

>>10784727
>from a current is a CHARGE IN MOTION
That's the definition of current. I.e: "charge" running along a wire. This charge will only induce current in a second wire when it's changing. For example, if you charge a capacitor with a wire, the inrush current will be able to induce current in a parallel wire during that moment. If you run AC through that first wire, then it will continuously induce current in the second, if you coil both of them and keep them close, you get an air core transformer. Supposedly the earth's magnetic field changes polarity over time, which suggests a very low frequency AC current, not DC

[Anonymous No.10784763]

>>10784735
>The Sun's magnetic field is sufficient to serve as a seed for Earth
That's one theory, but the mantle would shield the outer core from it, which is why they came up with the (likely bullshit) explanation that it's ions and sheeyt in the boundary layers between inner core, outer core and mantle

[Anonymous No.10784808]

>>10784675
>But the magnetic field can exist without the electric current. Think of a regular magnet.

the think is that you need a current to magnetize an object and then it becomes magnetized, or you need a current to sustain a magnetize state and this proposition is very interesting because theres some theories that propose this is the case, the sun would be the one that creates charges in motion that sustain the earths magnetic field (and other planets ) or that at least the sun can interfere with the earths magnetic field directly by his current (or charges in motion if you want to be pesky about it)

or maybe the earth magnetic field is just there from the very beginning but supposedly the earth was born as a very hot object and then it cool off (just the crust because the center supposedly is still very hot) but we know that very high temps will demagnetize a remanent magnetic field... and from what I understand the earth field depends on iron so is not even a "rare earth" type of magnet that could hold much more remanent field or withstand higher temps than iron... some people say its all because of the preassures the iron sees in the core of the earth that allows it to sustain it this long...

[Anonymous No.10784834]

>>10784759
>This charge will only induce current in a second wire when it's changing

the charges in motion creates a magnetic field around themself!!!!
this is why it is called "electromagnetism" because they are intrinsic to one another (this is kinda similar to what "spacetime" is, they are intrinsic, if the general relativity theory is correct that is)

and also this is why in electronics you have to be very carefull when designing high speed circuit in term of the layout because at high frequencies every cable or even the leads from the components becomes an antenna radiating and also absorving magnetic fields within the circuit creating feedback loops and all kinds of bad behaviour...this is also why high frequency work is hghly regarded in electronics because its an art to do good design and BTW if it looks pretty the chances are that it will not work so well...

("bug contruction" is super nice to do good high speed designs)

[Anonymous No.10785183]

>>10784834
>the charges in motion creates a magnetic field around themself!!!!
Yes but a conductor simply being in a static magnetic field has no current going through itself.

[Anonymous No.10785457]

>>10785183
ah, I see what you mean , yes both require a "movement of the field or charge" to generated the other. but this assertion can be tricky because it dont necessarely mean only AC currents ot fields generate the other. you can have a permanent magnet (a "DC magnetic field") produce a dc current by moving it but without changing his polarity (meaning without strictly goin into AC opperation, with polarity reversal) this in practice becomes cumbersome and actually using an AC magnetic field (meaning with polarity reversal) is more practical for machines.

[Anonymous No.10785507]

>>10785457
>produce a dc current by moving it but without changing his polarity
The current will alternate as the magnetic field passes by the conductor, the magnet itself doesn't change its polarity, it's just that at one point it's coming closer to the conductor, after it it's distancing itself. If you stop abruptly, the magnetic field in the conductor will generate a current in reverse as it breaks up

https://www.youtube.com/watch?v=vwIdZjjd8fo

[Anonymous No.10786853]

>>10785507
this is why I said "practical machines" , that demostration is the typical case for "circular generator" but you could have a linear generator where you just keep moving but keeping the same "DC" magnetic polarity and resulting in a DC current. this is not such a practical machine as the ubiquitous circular type .

for example in this animation you could keep going in only one direction producing only a DC
current but because of practical constrains (the magnet has an "end" )you have to go back in the other direction if you want to keep producing current (but now it will be an AC current)

[Anonymous No.10788600]

>>10783860
>outer core would need to be inside an alternating magnetic field already.

The radiation pressure that helps to keep the Earth in a stable orbit around the sun is like a huge electron orbital. That's basically what you are seeing when you stand up a bar magnet near ferrous metal fragments. The metal fragments align with the two dimensional surfaces of charge generated by the magnet, which are electron orbitals. The entire solar system is held in equilibrium by the magnetic field generated by the sun, more so than gravity. Maybe. That magnetic field is composed of many two dimensional surfaces forming spheres of charge, maybe. If this were the case, it would certainly explain how the mantle is able to generate a magnetic field, maybe. I don't fucking know.

[Anonymous No.10789205]

>>10783860
>Electric current
Ferromagnetism doesn't require electric current to work, just a spin order in one direction.
Presumingly through extremely high pressure all spins in iron of the Earth's core are forcefully being put in one parallel direction forcing the magnetic field to expand outwards instead of being surpressed by domains inside it.