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

Um supercondutor é um material que oferece resistência zero ao fluxo de elétrons com uma transferência eficiente de energia elétrica e sem perda de calor.
Em 1911, Heike Kamerlingh Onnes observou que a resistência vai para zero quando o mercúrio é resfriado abaixo de 4,2 Kelvin. Isso é conhecido como temperatura crítica para mercúrio, e o fenômeno é conhecido como supercondutividade.
Quando a temperatura aumenta acima da temperatura crítica, a resistência muda linearmente com ela.
Outro aspecto do comportamento magnético de um supercondutor é observado quando um material supercondutor homogêneo é colocado em um campo magnético uniforme externo.
Quando a temperatura é maior que a temperatura crítica, o campo dentro do material é igual ao campo magnético uniforme externo. Se for menor que a temperatura crítica, o fluxo magnético é expelido do material e o campo dentro dele é zero. Esse fenômeno é conhecido como efeito Meissner.
A supercondutividade de um material abaixo da temperatura crítica pode ser eliminada aplicando a magnitude mínima do campo magnético, conhecida como campo magnético crítico.

<ol>
	<li>OpenStax. (2019). Física Universitária Vol. 2. [Versão Web], Pg 396 - 398. Obtido 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>

supercondutor

Uma substância que atinge a supercondutividade, um estado no qual campos magnéticos não conseguem penetrar e não há resistência elétrica, é chamada de supercondutor. Em 1911, Heike Kamerlingh Onnes da Universidade de Leiden, um físico holandês, observou uma relação entre a temperatura e a resistência do elemento mercúrio. A amostra de mercúrio foi então resfriada em hélio líquido para estudar a dependência linear da resistência com a temperatura. Foi observado que, conforme a temperatura diminuía, a resistência caia. Kamerlingh Onnes continuou resfriando ainda mais a amostra de mercúrio e, à medida que a temperatura se aproximava de 4,2 K, a resistência abruptamente chegava a zero. Essa é a temperatura crítica para o mercúrio, onde a amostra de mercúrio entra em uma fase com resistência absoluta zero, e esse fenômeno é conhecido como supercondutividade. No caso de condutores, a resistência não é igual a zero, mas é inferior a 0,01 Ω. Existem vários métodos para medir resistências muito pequenas, como o método dos quatro pontos, mas um ohmímetro não é aceitável para testar a resistência de supercondutividade.

Depois disso, descobriu-se vários outros materiais que chegam na fase supercondutora quando a temperatura chega próxima ao zero absoluto. Em 1941, foi descoberto que uma liga de nióbio-nitrito se torna supercondutora a 16 Kelvin; da mesma forma, em 1953, descobriu-se que o vanádio-silício se torna supercondutor a 17,5 Kelvin. As temperaturas para a transição para a supercondutividade estavam lentamente aumentando. Surpreendentemente, muitos materiais que são bons condutores, como cobre, prata e ouro, não exibem supercondutividade.

Supercondutor

Uma substância que atinge a supercondutividade, um estado no qual os campos magnéticos não podem penetrar e não há resistência elétrica, é chamada de ...

Education

JoVE Core

Física

Unit 1

Unidade 1

Electromagnetic Induction

Indução Eletromagnética

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

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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

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faraday's law

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lenz's law

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motional emf

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faraday disk dynamo

Faraday Disk Dynamo and DC Output

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induced electric fields

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induced electric fields: applications

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eddy currents

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displacement current

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significance of displacement current

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electromagnetic fields

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maxwell's equation of electromagnetism

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symmetry in maxwell's equations

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electric generator: alternator

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back emf

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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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