Name: superconductor critical temperature
Uploaded: 2025-05-22T09:05:52.000Z
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K12 Standards

Virginia  Standards of Learning

HIgh School

Physics

PH.9

PH.9.g

Superconductor

Un supraconducteur est un matériau qui offre une résistance nulle au flux d’électrons avec un transfert efficace d’énergie électrique et aucune perte de chaleur.
En 1911, Heike Kamerlingh Onnes a observé que la résistance descend à zéro lorsque le mercure est refroidi en dessous de 4,2 Kelvin. C’est ce qu’on appelle la température critique pour le mercure, et le phénomène est connu sous le nom de supraconductivité.
Lorsque la température augmente au-dessus de la température critique, la résistance change linéairement avec elle.
Un autre aspect du comportement magnétique d'un supraconducteur est observé lorsqu'un matériau supraconducteur homogène est placé dans un champ magnétique externe uniforme.
Lorsque la température est supérieure à la température critique, le champ à l’intérieur du matériau est égal au champ magnétique uniforme externe. S’il est inférieur à la température critique, le flux magnétique est expulsé du matériau et le champ à l’intérieur de celui-ci est nul. Ce phénomène est connu sous le nom d’effet Meissner.
La supraconductivité d’un matériau en dessous de la température critique peut être éliminée en appliquant l’amplitude minimale du champ magnétique, connue sous le nom de champ magnétique critique.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web], p. 396 à 398. Tiré de <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>

superconducteur

Une substance qui atteint la supraconductivité, un état dans lequel les champs magnétiques ne peuvent pas pénétrer et où il n'y a pas de résistance électrique, est appelée superconducteur. En 1911, Heike Kamerlingh Onnes de l'Université de Leyde, un physicien néerlandais, a observé une relation entre la température et la résistance de l'élément mercure. L'échantillon de mercure a ensuite été refroidi dans de l'hélium liquide pour étudier la dépendance linéaire de la résistance par rapport à la température. Il a été observé que, à mesure que la température diminuait, la résistance diminuait également. Kamerlingh Onnes a continué à refroidir l'échantillon de mercure davantage et, à mesure que la température approchait 4,2 K, la résistance est brusquement tombée à zéro. Il s'agit de la température critique du mercure, où l'échantillon de mercure entre dans une phase de résistance absolue zéro, et ce phénomène est connu sous le nom de supraconductivité. Dans le cas des conducteurs, la résistance n'est pas égale à zéro mais est inférieure à 0,01 Ω. Il existe différentes méthodes pour mesurer de très petites résistances, comme la méthode à quatre points, mais un ohmmètre n'est pas adapté pour tester la résistance à la superconductivité.

D'autres matériaux ont été découverts dans la phase de supraconductivité lorsque la température approche le zéro absolu. En 1941, un alliage de niobium-nitrure a été découvert pour devenir supraconducteur à 16 kelvin ; de même, en 1953, le vanadium-silicium a été découvert pour devenir supraconducteur à 17,5 kelvin. Les températures de transition vers la supraconductivité augmentaient lentement. Étonnamment, de nombreux bons conducteurs, tels que le cuivre, l'argent et l'or, ne présentent pas de supraconductivité.

Superconducteur

Une substance qui atteint la supraconductivité, un état dans lequel les champs magnétiques ne peuvent pas pénétrer et où il n’y a pas de résistance électrique, est appelée ...

Education

Enseignement

JoVE Core

Physique

Unit 1

Unité 1

Electromagnetic Induction

Induction électromagnétique

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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

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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...

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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

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Superconductor Critical Temperature

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