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Questions and Answers
What is the Meissner effect?
What is the Meissner effect?
- The expulsion of a magnetic field from a superconductor during its transition to the superconducting state (correct)
- The conservation of a magnetic field by a superconductor during its transition to the superconducting state
- The enhancement of a magnetic field within a superconductor during its transition to the superconducting state
- The attraction of a magnetic field by a superconductor during its transition to the superconducting state
Who discovered the Meissner effect?
Who discovered the Meissner effect?
- Isaac Newton and Albert Einstein
- Walther Meißner and Robert Ochsenfeld (correct)
- Thomas Edison and Nikola Tesla
- Marie Curie and Pierre Curie
What will happen to a nearby magnet when the Meissner effect occurs?
What will happen to a nearby magnet when the Meissner effect occurs?
- It will be unaffected by the superconductor
- It will oscillate around the superconductor
- It will be repelled by the superconductor (correct)
- It will be attracted to the superconductor
What happens to the interior magnetic fields of superconducting tin and lead samples during the Meissner effect?
What happens to the interior magnetic fields of superconducting tin and lead samples during the Meissner effect?
What is the nature of equilibrium that determines the ability for the expulsion effect in a superconductor?
What is the nature of equilibrium that determines the ability for the expulsion effect in a superconductor?
When does the Meissner state break down?
When does the Meissner state break down?
What happens when the strength of the applied field rises above a critical value in type-I superconductors?
What happens when the strength of the applied field rises above a critical value in type-I superconductors?
What occurs at a second critical field strength Hc2 in type-II superconductors?
What occurs at a second critical field strength Hc2 in type-II superconductors?
What is the name given to the electric current-induced motion of flux vortices in some type-II superconductors?
What is the name given to the electric current-induced motion of flux vortices in some type-II superconductors?
What does the London equation predict about the magnetic field in a superconductor?
What does the London equation predict about the magnetic field in a superconductor?
In a weak applied field, how does a superconductor expel nearly all magnetic flux?
In a weak applied field, how does a superconductor expel nearly all magnetic flux?
What is the manifestation of the phase transition from conductor to superconductor with respect to magnetic field exclusion?
What is the manifestation of the phase transition from conductor to superconductor with respect to magnetic field exclusion?
Which class of superconductors exhibits an intermediate state consisting of a baroque pattern of regions of normal material mixed with regions of superconducting material?
Which class of superconductors exhibits an intermediate state consisting of a baroque pattern of regions of normal material mixed with regions of superconducting material?
What term is used to describe the motion of flux vortices induced by the Lorentz forces from the current in some type-II superconductors?
What term is used to describe the motion of flux vortices induced by the Lorentz forces from the current in some type-II superconductors?
What property does a weak applied field induce near the surface of a superconductor with regard to magnetic flux expulsion?
What property does a weak applied field induce near the surface of a superconductor with regard to magnetic flux expulsion?
What is minimized in a superconductor according to the London equation?
What is minimized in a superconductor according to the London equation?
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Study Notes
Meissner Effect
- The Meissner effect is the expulsion of magnetic fields from a superconductor during its transition to a superconducting state.
- The Meissner effect was discovered by Walther Meissner and Robert Ochsenfeld in 1933.
Effects on Magnetic Fields
- When the Meissner effect occurs, a nearby magnet will be repelled.
- The interior magnetic fields of superconducting tin and lead samples are expelled during the Meissner effect.
Equilibrium and Expulsion
- The equilibrium state that determines the ability for the expulsion effect in a superconductor is thermodynamic equilibrium.
- The Meissner state breaks down when the strength of the applied field rises above a critical value.
Type-I and Type-II Superconductors
- In type-I superconductors, when the strength of the applied field rises above a critical value, the Meissner state breaks down.
- In type-II superconductors, when the applied field rises above a second critical field strength Hc2, the Meissner state breaks down.
- The motion of flux vortices induced by the Lorentz forces from the current in some type-II superconductors is called flux flow.
London Equation
- The London equation predicts that the magnetic field in a superconductor will decay exponentially with distance from the surface.
- In a weak applied field, a superconductor expels nearly all magnetic flux.
- The manifestation of the phase transition from conductor to superconductor is the exclusion of magnetic fields.
Intermediate State
- Type-I superconductors exhibit an intermediate state consisting of a baroque pattern of regions of normal material mixed with regions of superconducting material.
Magnetic Flux Expulsion
- A weak applied field induces perfect diamagnetism near the surface of a superconductor, expelling magnetic flux.
- According to the London equation, the magnetic field energy is minimized in a superconductor.
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