The Meissner Effect and Maglev Trains? (1 Viewer)

[Seomate]

Okay so I was discussing with my teacher about whether the Meissner effect applied to Maglev trains (where I disagreed with this and my teacher agreed with this). I stated that the Meissner effect stated that when a perfect eddy current (I say perfect because a superconductor has no resistance) generated an internal magnetic field powerful enough to totally oppose the external magnetic field in the opposite direction, thereby repelling the external magnetic field from the solid superconductor. So I questioned how a perfect eddy current could be generated in an on-board superconducting electromagnet in order to totally oppose the external magnetic field.

My teacher than told me that very small eddy currents were generated in the superconducting wire, so I told her that I thought only eddy currents were generated in solid conductors only and my teacher said no. I always thought that the induced current only followed the path of the wire?

TL: DR
Are eddy currents really generated in superconducting wires (or a superconducting electromagnet to be specific)? And do Maglev trains really use the Meissner effect?

 

[Demento1]

1. They are meissner surface currents, not eddy currents.
2. No, maglev trains have nothing to do with meissner effect. The EDS (electrodynamic suspension) maglev trains utilise superconducting electromagnets to create REALLY STRONG magnetic fields which allow it to levitate.

 

[Seomate]

1. They are meissner surface currents, not eddy currents.
2. No, maglev trains have nothing to do with meissner effect. The EDS (electrodynamic suspension) maglev trains utilise superconducting electromagnets to create REALLY STRONG magnetic fields which allow it to levitate.

So I'm correct and my teacher is wrong? Bts, waht is a meissner surface current? Are they similar to eddy currents? Or do they travel in the path of the wire?

 

[Demento1]

So I'm correct and my teacher is wrong? Bts, waht is a meissner surface current? Are they similar to eddy currents? Or do they travel in the path of the wire?

You are correct Essentially, cooper pairs move around as a large loop of current near the surface of the superconductor, called a meissner surface current, and this current loop creates its own magnetic field that completely expels all the external flux of the magnet from the interior of the superconductor, such that the net magnetic field in the superconductor is zero, which is what the meissner effect is.

 

[someth1ng]

They're called persistent currents, not meissner surface currents.

 

[anomalousdecay]

I swear HSC methods never explained this properly (tbh I found it took ages to figure out and I think I never really got what type of currents occurred because there were too many facts which were never explained about properly in the resources I had).

 

[someth1ng]

The problem wasn't the HSC not explaining properly but the fact that even teachers have lots of misconceptions about the content.

 

[Seomate]

The problem wasn't the HSC not explaining properly but the fact that even teachers have lots of misconceptions about the content.

do you think you could explain to me why the Meissner effect does not apply in Maglev trains?

 

[anomalousdecay]

The problem wasn't the HSC not explaining properly but the fact that even teachers have lots of misconceptions about the content.

That adds to the problem. However, there are a few things which are unaccounted for in my perspective. Then again I mainly used 2 or 3 resources and maybe 2 or 3 more here and there so I could be wrong and there could have been better resources out there that made more sense but I just didn't find them or something.

Oh for Phys, we didn't actually learnt phys in class. All we learnt was about random life stuff and how to maximise marks in HSC or sometimes we would just be bored and play with the class pet (yes we had a class pet believe it or not).

I mean all this stuff was a great way to relax from study or do things at my own pace, though I had to learn the content myself and still somehow managed my highest mark to be in Phys this way (maybe this style of teaching worked for me idk lol).

So I can't really comment much relevance on teaching misconceptions.

 

[someth1ng]

do you think you could explain to me why the Meissner effect does not apply in Maglev trains?

Meissner effect is about superconductors magically floating in the magnetic field - it's more like a property of superconductors. Maglev trains run using very strong magnets that repel or attract (depending on how the train is set up) which levitate the train and push/pull it forward.

There is absolutely no relationship between the Meissner effect and Maglev trains - apart from the fact that they involve things floating.

That adds to the problem. However, there are a few things which are unaccounted for in my perspective. Then again I mainly used 2 or 3 resources and maybe 2 or 3 more here and there so I could be wrong and there could have been better resources out there that made more sense but I just didn't find them or something.

Oh for Phys, we didn't actually learnt phys in class. All we learnt was about random life stuff and how to maximise marks in HSC or sometimes we would just be bored and play with the class pet (yes we had a class pet believe it or not).

I mean all this stuff was a great way to relax from study or do things at my own pace, though I had to learn the content myself and still somehow managed my highest mark to be in Phys this way (maybe this style of teaching worked for me idk lol).

So I can't really comment much relevance on teaching misconceptions.

Yeah, it's a mix of lots of things - poor syllabus which fails to teach the skills necessary for success at university level physics, generally poor teaching etc. It's something that really needs fixing but I don't really think many people have the guts to do it, unfortunately.

 

[jameeeesto]

"So I questioned how a perfect eddy current could be generated in an on-board superconducting electromagnet in order to totally oppose the external magnetic field." How can't it? Sorry, I'm confused by your reasoning as to why a perfect eddy current can't be formed.