Fritz Walther Meissner

created by dcho39

Personal Life

Fritz Walther Meissner was born in Berlin, Germany on December 16, 1882 to Waldemar Meissner and Johanna Greger. He was educated at the Technical University of Berlin, studying physics and mechanical engineering; his supervisor was Max Planck. After, he attended the Physikalisch-Technische Bundesanstalt in Berlin. In 1926, he became chair in technical physics at the Technical University of Munich. He also later became the president of the Bavarian Academy of Sciences and Humanities. Sadly, Meissner lived lonely for the last few years until his death in 1974, with only his two dogs to accompany him.

Scientific Contributions

Meissner Effect

Aided by fellow German physicist Robert Ochsenfeld, Meissner discovered this scientific phenomenon in 1933. The Meissner effect is when a superconductor expels all magnetic fields from its interior during its transition to the superconducting state. This finding was actually done so indirectly. The two scientists were observing how the magnetic flux is conserved by a superconductor. They found that their sample of tin and lead were cooled below their critical, or superconducting transition, temperature when in the presence of an applied magnetic field. At this point, almost all interior magnetic fields were neutralized.

Superconductor above and below critical temperature

Explanation

The Meissner effect was given a phenomenological explanation by the brothers Fritz and Heinz London, who showed that the electromagnetic free energy in a superconductor is minimized provided

where H is the magnetic field and λ is the London penetration depth. It is also called the London equation.

It states the the magnetic field weakens substantially as you go from the surface to the interior of the superconductor.

This is due to the superconductor creating electric currents at the surface that will cancel the magnetic field. This effect continues for a very long time as the cancellation is not dependent on time, which leads the superconductor to be thought of as always expelling magnetic fields.

Levitation due to a superconductor

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Further reading

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External links

• Meissner Effect (Hyperphysics)
• Historical Background of the Meissner Effect

References

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