Name: superconductor critical temperature
Uploaded: 2025-05-22T09:05:52.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physics

PH.9

PH.9.g

Superconductor

A superconductor is a material that offers zero resistance to the flow of electrons with an efficient transfer of electrical energy and no heat loss.
In 1911, Heike Kamerlingh Onnes observed that resistance goes to zero when mercury is cooled below 4.2 Kelvin. This is known as the critical temperature for mercury, and the phenomenon is known as superconductivity.
When the temperature increases above the critical temperature, the resistance changes linearly with it.
Another aspect of a superconductor&#39;s magnetic behavior is observed when a homogeneous superconducting material is placed in an external uniform magnetic field.
When the temperature is greater than the critical temperature, the field inside the material is equal to the external uniform magnetic field. If it is lower than the critical temperature, the magnetic flux is expelled from the material, and the field inside it is zero. This phenomenon is known as the Meissner effect.
The superconductivity of a material below the critical temperature can be eliminated by applying the minimum magnitude of the magnetic field, known as the critical magnetic field.

supergeleider

Een stof die supergeleiding bereikt, een toestand waarin magnetische velden niet kunnen doordringen en er geen elektrische weerstand is, wordt een supergeleider genoemd. In 1911 observeerde Heike Kamerlingh Onnes van de Universiteit Leiden, een Nederlandse natuurkundige, een verband tussen de temperatuur en de weerstand van het element kwik. Het kwikmonster werd vervolgens gekoeld in vloeibaar helium om de lineaire afhankelijkheid van de weerstand van de temperatuur te bestuderen. Er werd waargenomen dat naarmate de temperatuur daalde, de weerstand daalde. Kamerlingh Onnes bleef het kwikmonster verder afkoelen, en toen de temperatuur de 4,2 K naderde, ging de weerstand abrupt naar nul. Dit is de kritische temperatuur voor kwik, waarbij het kwikmonster in een fase komt met een absolute nulweerstand, en dit fenomeen staat bekend als supergeleiding. In het geval van geleiders is de weerstand niet gelijk aan nul, maar kleiner dan 0,01 Ω. Er zijn verschillende methoden om zeer kleine weerstanden te meten, zoals de vierpuntsmethode, maar een ohmmeter is niet acceptabel voor het testen van supergeleidingsweerstand. Er zijn verschillende andere materialen ontdekt in de supergeleidende fase, wanneer de temperatuur bijna het absolute nulpunt bereikt. In 1941 bleek een legering van niobiumnitride supergeleidend te worden bij 16 Kelvin; Op dezelfde manier bleek in 1953 vanadium-silicium supergeleidend te worden bij 17,5 Kelvin. De temperaturen voor de overgang naar supergeleiding slopen langzaam omhoog. Verrassend genoeg vertonen veel goede geleiders, zoals koper, zilver en goud, geen supergeleiding.

Supergeleider

A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a ...

Education

JoVE Core

Natuurkunde

Unit 1

Onderdeel 1

Electromagnetic Induction

Elektromagnetische inductie

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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 temperature fell, the resistance also fell. When the temperature approached 4.2 K, the resistance suddenly dropped to zero. That temperature is the critical temperature for mercury, and the mercury sample entered a superconducting phase with absolute zero resistance.

A normal conductor is different because its resistance is not zero, even when it is very small. In the transcript, conductors are described as having resistance less than 0.01 Ω. Very small resistances can be measured with methods such as the four-point method. An ohmmeter, however, is not acceptable for testing superconductivity resistance.

Other materials have also been found in the superconducting phase near absolute zero. In 1941, an alloy of niobium-nitride became superconducting at 16 kelvin. In 1953, vanadium-silicon became superconductive at 17.5 kelvin. These discoveries showed that transition temperatures were slowly increasing. Even so, many good conductors such as copper, silver, and gold do not show superconductivity.

Superconductor Critical Temperature

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

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dc generator

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magnetic damping

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superconductor

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 and Magnetic Levitation

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faraday's law

Magnetic Flux and Induced Emf

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lenz's law

Magnet Motion and Induced Current

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motional emf

Induced Current from Changing Magnetic Flux

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faraday disk dynamo

Faraday Disk Dynamo and DC Output

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induced electric fields

Faraday’s Law and Induced EMF

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induced electric fields: applications

Electric Fields from Changing Magnetism

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eddy currents

Eddy Currents in Recycling, Brakes, and Heat

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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

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electromagnetic fields

Electric and Magnetic Fields in Motion

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maxwell's equation of electromagnetism

Maxwell's Equations and Light Waves

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symmetry in maxwell's equations

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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

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key terms and concepts

Learn how superconductivity appears at a critical temperature, why mercury became a classic example, and how other materials also show zero resistance.

Superconductor Critical Temperature | JoVE K12

physics

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PH.9.e

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Superconductor Critical Temperature

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