How many Ampere in a superconducting spire?

In summary, a superconducting spire is a structure made of superconducting materials that can carry a large amount of electrical current without resistance. The amount of current that can flow through a superconducting spire is measured in Amperes, and it can reach up to several thousand Amperes. This makes superconducting spires ideal for use in high-power applications, such as in particle accelerators and fusion reactors. However, the exact number of Amperes that a superconducting spire can carry depends on various factors, such as the material used, the temperature, and the design of the spire itself.
  • #1
jumpjack
223
3
As far as I can understand, after inducing a current inside a superconducting ring or spire, the current keeps flowing into the ring "for ever". Is this correct?

Since electrons have no "friction" against the superconducting lattice, does this mean that I can virtually accelerate them "indefinitely", thus inducing an "indefinitely" high current?

I mean, if current is caused by electric force applied to electrons, and resistance is due to electrons friction against lattice, maybe they accelerate indefinitely as long as I apply the force?

"for ever" and "indefinitely" of cours refer to ideal conditions; so what does it actually happen in real world? How much a current can I induce into a superconducting ring?
 
Physics news on Phys.org
  • #2
The "model" you are using to describe what is happening in a superconductor is not quite correct.

However, the answer to the actual question is: it depends:cool:
The critical current density Jc of a real superconductor depends on many different factors: the type of superconductor (aluminium is very different from say YBCO), the temperature (lower T gives higher Jc), the structure of the material (mainly the amount and type of grain boundaries), the frequency (superconductors are only lossless at DC), the magnetic field etc.

Hence, the answer can be anything from say 100 A/cm^2 to 10^8 A/cm^2.

(note the units: a cable with cross-sectional area of 1 cm^2 and a a Jc of 100 A/cm^2 can carry 100 A of current)
 
  • #3
But how much voltage would I need to induce 100 A, being I=V/R law no more valid?
Can I apply multiple low-voltage pulses to get an high current, considering that current wouldn't stop flowing between a pulse and the other? Or do I need a constant high voltage?
 
  • #4
0 volts. You cannot apply a voltage across a superconductor.
 
  • #5
Dalespam is of course correct.
You can not "inject voltage" in a superconducting ring, you need a current source (or a voltage source with a suitable resitor in series).
 
  • #6
apart from the method, which is the max current achievable and which is the electrons speed?
 
  • #7
jumpjack said:
apart from the method, which is the max current achievable and which is the electrons speed?

Electron speed is a strange concept here. The cooper pairs have long-range coherence, which is the definition of superconductivity.

Maximum current depends on the superconductor. Look up "superconducting critical current density".

Zz.
 
  • #8
jumpjack said:
apart from the method, which is the max current?QUOTE]

I gave you that answer above, I'd say about 10^8 A/cm^2 (Ca doped YBCO at temperatures below 4K). However, I don't think anyone has ever achived that in a large scale structure.
 
  • #9
ZapperZ said:
Electron speed is a strange concept here. The cooper pairs have long-range coherence, which is the definition of superconductivity.
But this is like talking about lightspeed in a conductor, although electrons move at a few cm/sec in a conductor.

Apart from the EM propagation into a SC, I wonder if electrons in SC do behave more like "small balls" than like waves, having no obstacles to their movements around.
 
Last edited:
  • #11
jumpjack said:
But this is like talking about lightspeed in a conductor, although electrons move at a few cm/sec in a conductor.

Apart from the EM propagation into a SC, I wonder if electrons in SC do behave more like "small balls" than like waves, having no obstacles to their movements around.

I strongly suggest you learn a bit more about superconductivity before making such silly speculation.

Furthermore, you should also look up the average speed of electrons in a regular conductor. Do not confuse that with the drift velocity!

Zz.
 
  • #12
ZapperZ said:
I strongly suggest you learn a bit more about superconductivity before making such silly speculation.

Furthermore, you should also look up the average speed of electrons in a regular conductor. Do not confuse that with the drift velocity!

Zz.

any link? I'm not comfortable with English physics jargon.
 

FAQ: How many Ampere in a superconducting spire?

1. How is the current measured in a superconducting spire?

The current in a superconducting spire is measured using a device called a superconducting quantum interference device (SQUID). This device uses the principle of quantum interference to detect and measure the magnetic field created by the current flowing through the spire.

2. What is the maximum current that can flow through a superconducting spire?

The maximum current that can flow through a superconducting spire is determined by its critical current, which is the maximum current that can flow without causing the material to lose its superconducting properties. This critical current is dependent on factors such as the material used and the temperature of the spire.

3. Can the current in a superconducting spire be turned off?

Yes, the current in a superconducting spire can be turned off by raising its temperature above its critical temperature. This causes the material to transition from a superconducting state to a normal conducting state, where resistance is present and the current can be turned off.

4. How is a superconducting spire different from a regular spire?

A superconducting spire differs from a regular spire in that it is made of a material that can conduct electricity with zero resistance when cooled below its critical temperature. This allows for the flow of large amounts of current without any energy loss, making it highly efficient for applications such as power transmission and magnetic levitation.

5. What are the potential applications of superconducting spires?

Superconducting spires have a wide range of potential applications, including in power transmission, medical imaging, particle accelerators, and magnetic levitation systems. They are also being researched for use in quantum computing and high-speed trains.

Back
Top