On the magnetic field in the Meissner effect

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Discussion Overview

The discussion revolves around the behavior of the magnetic field in the context of the Meissner effect, particularly focusing on the interaction between a magnet and a superconductor. Participants explore concepts such as flux focusing, the effects on magnetic field intensity, and the forces experienced by an energized conductor in proximity to both a magnet and a superconductor.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether the magnetic field of the magnet increases at a specific position due to the presence of the superconductor, or if it remains unchanged, suggesting a possible superposition of fields.
  • Another participant introduces the concept of "flux focusing," indicating that the local magnetic flux can increase due to the superconductor, as the magnetic field must find an alternative path to close the loop.
  • It is mentioned that flux focusing can lead to significant increases in magnetic field intensity in practical applications, with a potential factor of around 10.
  • Participants discuss the ampere forces acting on an energized conductor placed near the superconductor and the magnet, questioning whether the force with the superconductor (F1) can be greater than the force without it (F2).
  • There is a repeated emphasis on the differences in ampere force experienced by the wire in the presence and absence of the superconductor.

Areas of Agreement / Disagreement

Participants generally agree on the concept of flux focusing and its implications, but the discussion remains unresolved regarding the specific changes in magnetic field intensity and the comparative ampere forces (F1 and F2).

Contextual Notes

Participants express uncertainty about the exact nature of the magnetic field changes and the conditions under which the ampere forces are compared, indicating a need for further clarification on these points.

li dan
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As shown in the figure, in the Meisner effect, the magnetic field of the magnet bypasses the superconductor. My question is, does the magnetic B field belonging to the magnet increase at the arrow indicating position?
Or is there no change in the intensity of the magnetic field that belongs to the magnet? Is it just the superposition of the magnetic field of the magnet and the magnetic field of the superconductor?.
Is it also possible to ask, assuming that the energized conductor is placed at the position of the arrow, regardless of the force between the energized conductor and the superconductor, the ampere force between the energized conductor and the magnet is F1. The ampere force between the energized wire and the magnet after removal of the superconductor is F2, can F1 be greater than F2?
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Yes, the local flux can increase due to the presence of the superconductor. This is known as "flux focusing".
Essentially, the field has to "go" somewhere to close the loop, and since it can't pass through the superconductor it has to go through the space in between.

Flux focusing can be quite significant; in many practical applications (e.g. superconducting coplanar waveguides) it can easily give you a factor ~10 increase.
 
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f95toli said:
Yes, the local flux can increase due to the presence of the superconductor. This is known as "flux focusing".
Essentially, the field has to "go" somewhere to close the loop, and since it can't pass through the superconductor it has to go through the space in between.

Flux focusing can be quite significant; in many practical applications (e.g. superconducting coplanar waveguides) it can easily give you a factor ~10 increase.

Thank you very much for your answer. Assuming that the energized conductor is placed at the position of the arrow, regardless of the force between the energized conductor and the superconductor, the ampere force between the energized conductor and the magnet is F1. The ampere force between the energized wire and the magnet after removal of the superconductor is F2. So, F1 may be bigger than F2, right?
 
f95toli said:
Yes, the local flux can increase due to the presence of the superconductor. This is known as "flux focusing".
Essentially, the field has to "go" somewhere to close the loop, and since it can't pass through the superconductor it has to go through the space in between.

Flux focusing can be quite significant; in many practical applications (e.g. superconducting coplanar waveguides) it can easily give you a factor ~10 increase.
is to place the wire at the position of the arrow, the two ends of the wire connected to the battery into the current, the wire and the magnet between the Ampere force, in the case of superconductors and no superconductors, ampere force is different?
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