# superconductors, generation, transmission and transport Q (1 Viewer)

#### superhubert

##### Member
what did you guys put for this one? i thought it was a rather stupid q. with transport, were they refering to the transportation of electricity through lines and the energy benifits here, or were they talking about transport as in maglev trains etc. they could have worded it better......

#### great_gregory

##### I'm really just OK...
Well, in my opinion they were obviously talking about the Maglev train, because they mentioned the transmission of power in the point above the transport one.

#### Ronnie

##### Member
hmm hmm hmm

how bout both?

Superconductors have no resistance right? therefore you can create extremely powerful electromagnets! much more powerful than conventional electromagnets we have, and this powerful electromagnet can be used to generate power since the current never dissipates, it will continue to provide an alternating current to produce a changing magnetic field which can be used to turn the rotor and would provide enormous amount of electricity

For transmision, again since it has no resistance there would be no power loss despite the size of voltage or current of electricity hence it would make transformers obsolote in one respect .The safety around power lines would also be improved because there is no need to step up the voltage to what they do in the present moment.... more V = more likely it is to ionise the air and electrocute you

and Maglev trains.... which is obvious but I wrote enough already so you figure it out

#### NATMAN

##### Member
agree with roonie

#### 1234567

##### Member
wow, that 's reall good.
.......

J

#### juzza

##### Guest
Maglev? asves energy? hah!

I'm not gonna groan, because I agree with everyone that the exam was un-nervingly easy.. however, there were indeed some silly questions, such as this one.

Seriously, Maglev trains saving energy?? Anyone have any idea how much electricity is needed to lift the train off then ground then actaully MOVE it? Its freaking massive! Indeed the amount of electricity the system needs is one of the main hurdles to a commercial maglev system.

I understand what the question was getting at (i.e. saving chemical energy in fossil fuels, by using alternating electiromagnetic fields to move the train rather than a combustion engine)... but seriously... electricity doesn't just flow from powerlines... It has to be made somewhere, and that is in powerstations, primarily through fossil fuels!!???

But anyway. Something tells me we may have a lotta 90+ % this year....

J

#### juzza

##### Guest
Originally posted by Ronnie
hmm hmm hmm

how bout both?

Superconductors have no resistance right? therefore you can create extremely powerful electromagnets! much more powerful than conventional electromagnets we have, and this powerful electromagnet can be used to generate power since the current never dissipates, it will continue to provide an alternating current to produce a changing magnetic field which can be used to turn the rotor and would provide enormous amount of electricity

Very nice theory Ronnie, really. However, I will pont out that it's forgetting one thing. Don't forget the Conservation of Energy law, that states you can't make energy from nothing. If not for this law, your system mentioned above could theoretically go on forever. However, as the charge in the magnets must do WORK to move the rotor, there must be an equivalent energy reduction in the superconducting magnet. Ultimately, such a generation system would only work if the rotor was the superconducting elecrtomagnet (not the other way around), and the magnet was constantly fed power.

But hey! No more physics... so does it really matter?

#### molloby

##### New Member
Errr, wouldn't a maglev train with super conducting tracks and magnets in the base be able to levitate without electricity because the superconductor itself sets up a perfectly opposing magnetic field?

J

#### juzza

##### Guest
Originally posted by molloby
Errr, wouldn't a maglev train with super conducting tracks and magnets in the base be able to levitate without electricity because the superconductor itself sets up a perfectly opposing magnetic field?
Exactly true!! It will! However, MOVING it is another thing entirely. This requires the creation of forces and involves work. Superconductors will not give you energy (such as the mechanical energy of a moving train) from nothing. You need to convert energy sources... not create them from nothing

#### superhubert

##### Member
no, it takes huge amounts of power to supercool the conductor to make it superconducting. the maglev train in japan runs on liquid nitrogen and is actual less energy efficient than a normal one. plus you have to power the magnets in the sides of the track to alternativly attract and repel the train. but i think the crux of the question was what would happen if superconductors operated at room temp. so then it would lift itself without energy. but you'd still have to move it. (but it would be heaps more energy efficient) so in a sense you were right.....

#### kini mini

##### Active Member
I just bit my tongue and claimed that superconductors in maglev trains would lead to energy savings as there'd be no friction with the track . It seemed to be what they wanted.

#### Winsux

##### Member
well either i totally stuffed that bit up, but i thought by transportation, it meant transportation of electricity, as in, with superconductive wires, you don't need very thick wires, and no heat is lost, because of the superconductive properties etc.

does anyone use the jacaranda physics book? its the best, and it goes into detail about this, plus the storage of electricity using semiconductors etc.

#### Ace-Pilot

##### Member
Oh ******* Great, I forgot to mention maglev trains, god damn wording bullcrap.

#### BlackJack

##### Vertigo!
There'd also be a esecond problem with moving trains with superconductors below...
When you tried to push a magnet hovering over the superconductor it resisted movement also because of Lenz's Law... in the same way, the superconductor- magnet pairs below the train would strongly resist any sideways movement, resulting in even more energy required to move the train... there's something wrong here...

I'd agree on how the maglev train would require energy because of the need for liquid nitrogen. "...nullify the energy benefits derived from no friction..." or something...

#### superhubert

##### Member
never thought of that...... anyway it was probably the worst worded question in the test. and they didn't give us enough room to answer it. (i let them know this next to the question.) there was as much weighting and space for the q on the pendulum prac where we had to explain whose method was best.......stupid.

#### kaseita

##### Member
huh? how would lenz's law resist the motion?
Sure, the superconductor under the train will repel the superconductor below the train, but its not exactly going to induce a current in the superconductor below, because the superconductor below will expel the magnetic field from the superconductor above. In other words, neither magnetic field is going to affect the other. (and I don't think they're dumb enough to use platforms made out of metal, without insulating material, because then the magnetic fields would create an effective electromagnetic braking effect)
So the only thing they will do is just repel each other, on the vertical plane. Not on the horizontal plane...

#### superhubert

##### Member
hmmmm. sticks it to BlackJack! bloody good point. eddy currents couldn't be introduced unless the magnets are to strong and they penetrated the superconductor. in which case it would cease to superconduct anyway.....

#### -=«MÄLÅÇhïtÊ»=-

##### Gender: MALE!!!
added to roonie's response, i said that instead of a soft iron core in the rotor, the use of superconductors would induce 0 eddy currents, plus the ceramic material is much lighter and smaller than soft iron, so the rotor is easier to turn.

and wiv maglev's, no friction is lost to the rails, like our current tangara trains which run on DC.

And since it's a discuss question i spoke about the costs of using superconductors. It was pretty much a textbook answer.

#### BlackJack

##### Vertigo!
Originally posted by kaseita
huh? how would lenz's law resist the motion?
Sure, the superconductor under the train will repel the superconductor below the train, but its not exactly going to induce a current in the superconductor below, because the superconductor below will expel the magnetic field from the superconductor above. In other words, neither magnetic field is going to affect the other. (and I don't think they're dumb enough to use platforms made out of metal, without insulating material, because then the magnetic fields would create an effective electromagnetic braking effect)
So the only thing they will do is just repel each other, on the vertical plane. Not on the horizontal plane...
Actually, the entire Meissner effect depends on Lenz's Law... It's BECAUSE of the eddy currents in the superconductor that there's no magnetic field penetrating it, and the magnets stay blanaced. And in this ideal situation, eddy currents in the superconductor produce practically no heat. But, if you tried to push the magnet down, (attempting to make the mag field penetrate the superconductor) there'd just be more eddy currents to oppose your motion.

The idea of the maglev is to have superconductor tracks with magnets balanced on top of them (or vice versa, it really doesn't matter).

This works horizontally too, see the magnets falling through the copper tube.

#### kaseita

##### Member
ahh gotya! that makes sense

oh well, then you do have a problem