Name: superconductors and magnetic levitation
Uploaded: 2025-05-22T09:05:52.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physics

PH.9

PH.9.g

Types Of Superconductors

Wenn ein Permanentmagnet über irgendeine Art von supraleitendem Material gelegt wird, wird der Magnet abgestoßen und schwebt aufgrund des Meissner-Effekts in einer stabilen Position. Supraleiter werden aufgrund ihres Verhaltens und ihrer Eigenschaften in Typ-I- und Typ-II-Gruppen eingeteilt.
Supraleiter vom Typ I fungieren als Leiter, wenn sie bei Raumtemperatur betrieben werden. Bei einer Abkühlung unter die kritische Temperatur wird jedoch die molekulare Bewegung im Inneren der Substanz reduziert, so dass der Strom so frei wie möglich fließen kann.
Sie bestehen typischerweise aus reinen Metallen wie Quecksilber, Zink, Aluminium, Blei usw. und gehorchen voll und ganz dem Meissner-Effekt, während sie ein geringes kritisches Magnetfeld haben.
Typ-II-Supraleiter weisen bei mittleren Temperaturen und Feldern oberhalb der supraleitenden Phasen eine Zwischenphase mit gemischten gewöhnlichen und supraleitenden Eigenschaften auf.
Sie bestehen typischerweise aus elementarem Niob, Vanadium, Technetium und Metalllegierungen oder komplexen Oxiden.
Typ-II-Supraleiter gehorchen teilweise dem Meissner-Effekt und verfügen über zwei kritische Magnetfelder.

<ol>
	<li>OpenStax. (2019). Universitätsphysik Vol. 2. [Web-Version], Seite 396 - 398. Abgerufen von <a href="https://openstax.org/books/university-physics-volume-2/pages/9-6-superconductors">https://openstax.org/books/university-physics-volume-2/pages/9-6-superconductors</a></li>
</ol>

arten von supraleitern

Ein Supraleiter ist eine Substanz, die keinen Widerstand gegen den elektrischen Strom bietet, wenn sie unter eine kritische Temperatur fällt. Null Widerstand ist nicht das einzige interessante Phänomen, wenn Materialien ihre Übergangstemperaturen erreichen. Ein zweiter Effekt ist die Ausschließung magnetischer Felder. Dies wird als der Meißner-Effekt bezeichnet. Ein leichter Dauermagnet, der über einer supraleitenden Probe platziert wird, schwebt in einer stabilen Position über dem Supraleiter. Hochgeschwindigkeitszüge, die auf starken supraleitenden Magneten schweben, wurden entwickelt, um die Reibung zwischen Zug und Gleisen zu beseitigen. Am 3. April 1997 wurde die Yamanashi-Maglev-Teststrecke in Japan offiziell eröffnet, und im April 2015 erreichte das Testfahrzeug MLX01 eine Geschwindigkeit von 374 km/h unter Verwendung starker supraleitender Magneten.

Supraleiter können in Typ-I- und Typ-II-Supraleiter kategorisiert werden.

Dreißig reine Metalle haben unterhalb ihrer kritischen Temperatur einen spezifischen Widerstand von Null und weisen den Meißner-Effekt auf, die Eigenschaft, magnetische Felder aus dem Inneren des Supraleiters auszuschließen, während der Supraleiter eine Temperatur unterhalb der kritischen Temperatur aufweist. Diese Metalle werden als Typ-I-Supraleiter bezeichnet. Die Supraleitfähigkeit besteht nur unterhalb ihrer kritischen Temperaturen und unterhalb einer kritischen magnetischen Feldstärke. Typ-I-Supraleiter haben begrenzte praktische Anwendungen, da die Stärke des kritischen Magnetfelds, das benötigt wird, um die Supraleitfähigkeit zu zerstören, recht niedrig ist.

Typ-II-Supraleiter haben viel höhere kritische Magnetfelder und können viel höhere Stromdichten tragen, während sie im supraleitenden Zustand bleiben. Verschiedene Keramikmaterialien, die Barium-Kupfer-Oxid enthalten, haben viel höhere kritische Temperaturen für den Übergang in einen supraleitenden Zustand. Supraleitende Materialien, die zu dieser Unterkategorie der Typ-II-Supraleiter gehören, werden oft als Hochtemperatursupraleiter kategorisiert.

Arten von Supraleitern

Ein Supraleiter ist eine Substanz, die dem elektrischen Strom keinen Widerstand bietet, wenn er unter eine kritische Temperatur fällt. Nullwiderstand ist nicht das Ziel ...

Education

Lehre

JoVE Core

Physik

Unit 1

Einheit 1

Electromagnetic Induction

Elektromagnetische Induktion

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

superconductors and magnetic levitation

Superconductors are materials that can carry electric current with zero resistance when they are cooled below a critical temperature. At this point, they also show the Meissner effect, which means they push magnetic fields out of their interior. A light permanent magnet can then levitate in a stable position above the superconducting sample.

This magnetic levitation has real uses. High-speed trains have been built with strong superconducting magnets so they can float above the track and avoid friction. The Yamanashi Maglev test line in Japan opened on April 3, 1997. In April 2015, the MLX01 test vehicle reached 374 mph using strong superconducting magnets.

Superconductors are grouped into Type I and Type II superconductors. Type I superconductors are about thirty pure metals that show zero resistivity below their critical temperature and also display the Meissner effect. They work only below their critical temperature and below a critical magnetic field strength. Because that critical magnetic field is low, Type I superconductors have limited practical use.

Type II superconductors can stay superconducting in much higher magnetic fields. They can also carry much higher current densities while remaining in the superconducting state. Many ceramic superconductors that contain barium-copper-oxide fall into this group. These materials often have much higher critical temperatures, so they are often called high-temperature superconductors.

Superconductors and Magnetic Levitation

induction

Magnetic Flux and Induced Current

Magnetic flux and induced current are linked when a magnetic field changes near a coil. Moving a bar magnet into or out of a coil induces an emf, which is an electromotive force. If the motion goes in the opposite direction, the emf has the opposite sign. Reversing the magnet poles also reverses the direction of the induced emf. The same effect appears when the coil moves instead of the magnet. Relative motion is what matters. A faster motion produces a larger emf. If the magnet and coil stay...

ampere-maxwell's law: problem-solving

Displacement Current in an RC Circuit

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differential form of maxwell's equations

Maxwell’s Equations at a Point

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dc generator

How a DC Generator Makes Current

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magnetic damping

Eddy Currents and Magnetic Braking

Eddy currents can create strong drag on moving objects. This drag is called magnetic damping. A metallic pendulum bob swinging between the poles of a strong magnet feels this force as it enters and leaves the field, so its motion dies out quickly. The effect is much smaller for a slotted metal plate. As the plate enters the magnetic field, a changing flux induces an emf, or electromotive force. The slots limit the size of the current loops, and nearby loops can carry currents in opposite...

superconductor

Superconductor Critical Temperature

Superconductivity is the state in which a material has no electrical resistance and magnetic fields cannot penetrate it. A material that reaches this state is called a superconductor. The key idea in the transcript is the critical temperature, which is the temperature at which the change happens. Heike Kamerlingh Onnes of Leiden University first observed this behavior in mercury in 1911. He cooled a mercury sample in liquid helium to study how resistance changed with temperature. As the...

types of superconductors

Superconductors are materials that can carry electric current with zero resistance when they are cooled below a critical temperature. At this point, they also show the Meissner effect, which means they push magnetic fields out of their interior. A light permanent magnet can then levitate in a stable position above the superconducting sample. This magnetic levitation has real uses. High-speed trains have been built with strong superconducting magnets so they can float above the track and avoid...

faraday's law

Magnetic Flux and Induced Emf

Faraday’s law connects magnetic flux changes to induced emf, or voltage. A change in the magnetic field or in the coil’s orientation with respect to the field can produce this voltage. Magnetic flux describes how many magnetic field lines pass through a given surface area.

lenz's law

Magnet Motion and Induced Current

Magnet motion and induced current are linked by Lenz’s law. The law says that the induced emf, or electromotive force, drives current around a wire loop in a direction that opposes the change in magnetic flux that caused it. A moving bar magnet can create this effect in a coil. If the magnet moves toward the coil, the magnetic flux increases and an induced current appears. That current produces a magnetic field that pushes against the stronger field from the magnet. The same idea works in...

motional emf

Induced Current from Changing Magnetic Flux

Induced current from changing magnetic flux depends on how a magnetic field interacts with an area. Magnetic flux changes when the field strength changes, when the area it passes through changes, or when the field turns relative to the surface. When any of these factors vary, the magnetic flux also varies. A change in area can happen in two common ways. The flux through a rectangular loop increases as the loop moves into a magnetic field. The magnetic flux through a rotating coil also changes...

faraday disk dynamo

Faraday Disk Dynamo and DC Output

A Faraday disk dynamo is a DC generator that produces an emf constant in time. It uses a conducting disk that spins at constant angular velocity in a magnetic field. The magnetic field is perpendicular to the plane of the disk. As the disk rotates, the magnetic flux changes and an emf is induced. This causes opposite charges to build up at the rim and at the center of the disk. The direction of the induced emf depends on the direction of the magnetic field and the direction of rotation. If...

induced electric fields

Faraday’s Law and Induced EMF

Faraday’s law explains how a changing magnetic flux can create an induced emf in a circuit. When current is induced, work is being done on the conduction electrons in the wire. That work must come from a source, and the source is not a battery or a magnetic field. A battery does not have to be present in a circuit for current to be induced. Magnetic fields also do not do work on moving charges. Instead, the change in magnetic flux produces an electric field in the wire. This is called an...

induced electric fields: applications

Electric Fields from Changing Magnetism

An electric field can be induced by a changing magnetic field. This induced electric field is nonconservative, which means it does not do net work when a charge moves around a closed path. That behavior is different from an electrostatic field, which comes from a fixed charge distribution. An electrostatic field is conservative, so it does no net work over a closed path. Because of this difference, electric potential can be linked to the electrostatic field, but not to the induced field. When...

eddy currents

Eddy Currents in Recycling, Brakes, and Heat

Eddy currents affect how metals move, stop, and heat up. They form only in conductors, so they are useful for separating metals from nonmetals and for other practical devices. In recycling centers, trash can be sent down a ramp under a strong magnet. Metals in the trash slow down because eddy currents resist their motion. Nonmetals keep moving, so the materials separate. This method works for metals in general, not only ferromagnetic ones. Eddy currents also help in metal detectors. A...

displacement current

Maxwell’s Fix for Changing Currents

Maxwell’s correction to Ampère’s law explains how changing electric fields can create magnetic fields. The key idea is the displacement current, Id, which Maxwell added to the real conduction current, I. This extra term helps the law work when current is not steady. The displacement current is defined using the permittivity of free space, ε0, and the electric flux, ΦE. It is not a real flow of charge. Instead, it is an added term in Maxwell’s equations that acts like current in Ampère’s law. <br...

significance of displacement current

Maxwell’s Fix for Charging Capacitors

Maxwell’s fix for a charging capacitor is the displacement current in Ampère’s law. A displacement current is not a flow of charge like conduction current. It comes from a changing electric field. That is why it is defined using a time-varying electric field and has its own displacement current density. Maxwell added this term to the original Ampère’s law. The result is called generalized Ampère’s law. The added displacement current term lets the law work in regions where no charges are moving.

electromagnetic fields

Electric and Magnetic Fields in Motion

Electric and magnetic fields can come from different sources, but they can act in surprisingly similar ways. Static charges create electrostatic fields. These fields are conservative, which means a test charge does no net work after moving around a complete loop. Fields made by changing magnetic fields behave differently. They are not conservative, and they do net work on a charge. That work is proportional to how fast the magnetic flux changes. These fields also do not follow Gauss’s law for...

maxwell's equation of electromagnetism

Maxwell's Equations and Light Waves

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symmetry in maxwell's equations

Electric and Magnetic Field Symmetry

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electric generator: alternator

How Alternators Produce AC Power

Alternators produce alternating current by rotating a conducting loop in a magnetic field. As the loop turns inside the field, the magnetic flux through the coil changes with time. That changing flux induces an emf, or electric voltage, in the circuit. A simple alternator uses a loop placed in a uniform magnetic field. The loop connects to split rings, and brushes carry the current to the external circuit. As the loop rotates, the magnetic flux changes sinusoidally, so the induced emf also...

back emf

Motor Current and Speed Changes

Motor current and speed changes are linked by back emf in an electric motor. A motor sends current through a wire loop in a magnetic field. The magnetic field pushes on the loop and creates torque, which turns a shaft and does mechanical work. As the coil turns, the magnetic flux through it changes. That changing flux induces an emf, or voltage, by Faraday’s law. The motor then acts like a generator whenever its coil rotates, whether the shaft is turned by an external drive or by the motor...

key terms and concepts

Learn how superconductors show zero resistance, the Meissner effect, and magnetic levitation, then compare Type I and Type II superconductors.

Superconductors and Magnetic Levitation | JoVE K12

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Superconductors and Magnetic Levitation

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