How super are superconductors?

By: Staff

What happens to current sent through a superconducting wire?

Superconductors have zero resistance, so current sent through such a wire loses no energy.

Who discovered superconductivity?

Dutch physicist Heike Kamerlingh Onnes and his collaborators, Cornelis Dorsman, Gerrit Jan Flim and Gilles Holst discovered superconductivity. The research of Johannes Diderik van der Waals -- a fellow countryman and contemporary physicist famous for the forces, molecules, radii and equation of state that bear his name -- helped inspire Onnes’ work. Hugo Christiaan Hamaker, another Dutch scientist, was an experimental physicist famous for his statistical work.

In what year did Onnes discover it?

When it was first identified by Dutch physicist Heike Kamerlingh Onnes in 1911, superconductivity flew in the face of established physics. In fact, an entirely new kind of physics, quantum mechanics, would have to be established before anyone had a hope of cracking the mystery of how the phenomenon worked.

Approximately how cold do conventional superconductors have to get before they enter the superconducting state?

Superconductors only function at very cold temperatures, on the order of 39 K for conventional superconductors (the solid mercury wire that Kamerlingh Onnes used had to be cooled below 4.2 K) and below around 130 K for modern, high-temperature superconductors. As for absolute zero, it cannot be achieved artificially, although laser cooling has taken us within one billionth of a degree of it.

Superconductors cease being superconductors if they are exposed to which of the following?

Just as superconductors have a critical temperature that separates them from normal conductors, they also have a critical magnetic field that hits them like kryptonite. Too much current will also take superconductors from hero to zero.

Which of the following do NOT currently use superconductors?

Although low critical magnetic fields limited the usefulness of older Type I superconductors for magnetic applications, modern Type II superconductors, such as niobium-titanium (NbTi), can handle much higher magnetic loads. Because they produce higher magnetic fields than, say, electromagnets made from copper wire, they have proven invaluable in MRI machines and proton accelerators.

How well a material conducts electricity has to do with what factor?

Good electrical conductors have atomic structures that readily give up electrons, moving them from the valence energy level to the conductance energy level. The result is a large number of free electrons available to carry current. Thus, the two answers essentially describe the same thing.

You can describe the structure of a typical conductor as which of the following?

A conductor is composed of a lattice of atoms, like a tiny jungle gym in which the intersections represent atoms and the connecting rods stand in for interactive forces. A bevy of bosons would be a boon to behold, but bears no relation to a typical conductor. Thanks to Alaskan Sen. Ted Stevens, everyone knows that the Internet is a series of tubes.

What of the following is NOT a source of resistance in a typical conductor?

The more deformed the lattice of the material is, the more likely it is that it will interfere with the free flow of electrons. The same is also true for higher temperatures, which cause the lattice and its component atoms to vibrate and oscillate faster. Cold, as a rule, decreases resistance.

What happens to a superconductor when it is cooled to its critical temperature?

As a superconductor is cooled, its resistance gradually drops until the critical temperature is reached, after which all resistance abruptly disappears. The substance has undergone a phase transition from conventional material to superconductor.

What are Cooper pairs?

In a superconductor, two electrons pair off to gain a net advantage when dealing with the ions that make up the material lattice. As the electron passes through the positively charged lattice, it attracts the surrounding atoms toward it. As they bunch up, these atoms create a local area of higher positive charge, which increases the force pulling the second electron forward. Consequently, the energy spent to get through, on average, breaks even.

What is the name of the theory that explains how conventional superconductors work?

Superconductors were known for almost half a century before, in 1957, physicists John Bardeen, Leon N. Cooper and John Robert Schrieffer finally advanced a theory that worked. In their honor, this fundamental theory of superconductivity is generally known as the Bardeen-Cooper-Schrieffer, or BCS, theory. In case you're wondering, XTC was a New Wave band from Swindon, England, and "The Aquitaine Progression" was a book by Robert Ludlum, but it sounded cool.

Today, superconductors that fit the BCS model are called "classical." What's the designation for superconductors that do NOT jibe with this theory?

Within a decade or two of the BCS theory being published, researchers began discovering other superconductors, such as heavy-fermion systems and high-temperature superconducting cuprates that broke the model. Today, superconductors that fit the BCS model are called “classical,” while those that don’t are known as "exotic." The means by which these exotic superconductors operate remains the subject of hot debate. "Strange" and "top" are designations used to describe quarks.

Which of the following elements become superconductors at low temperatures and pressures?

Hundreds of materials, including 27 metallic elements -- such as aluminum, lead, mercury and tin -- become superconductors at low temperatures and pressures. Another 11 chemical elements -- including selenium, silicon and uranium -- transition to a superconductive state at low temperatures and high pressures. The magnetic elements chromium, cobalt, iron, manganese and nickel are not superconductors.

Most superconductors are what type of material?

The vast majority of superconductors are alloys or compounds.

Which type of superconductor exhibits perfect diamagnetism in every superconducting state?

When cooled below its critical temperature, a Type I superconductor not only exhibits zero electrical resistivity, it also displays perfect diamagnetism. Type II superconductors display perfect diamagnetism while in one superconducting state but not in the other.

What is the vortex state?

A Type II superconductor has two critical magnetic fields. While between these two levels, it reorganizes into a mixed state -- a <i>vortex state</i> -- in which small whirlpools of superconducting current flow around cores of normal material.

What year ushered in the age of high-temperature superconductors?

Until 1986, when IBM researchers Karl Alexander Müller and Johannes Georg Bednorz ushered in the age of high-temperature superconductors with a barium-lanthanum-copper oxide that achieve zero resistance at 35 K (minus 238 C, minus 397 F), the highest critical temperature achieved by a superconductor was 23 K (minus 250 C, minus 418 F).

Which of the following has NOT been used as a coolant for superconductors?

Low-temperature superconductors required cooling by liquid helium, which is expensive and difficult to produce, but high-temperature superconductors can use liquid nitrogen, easily made from air, as coolant.

In 2000, Andre Geim and Sir Michael Berry won the Ig Nobel Prize for physics for doing what?

In 2000, Andre Geim Sir Michael Berry won the Ig Nobel Prize for physics by levitating a frog, as well as water and hazelnuts, with a superconductor, using diamagnetism. Alas, the world has yet to behold a superconducting snail, and MRI machines are far too heavy -- and large -- to effectively defenestrate.

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About This Quiz

In physics, you can’t get something for nothing, but superconductors offer the hope of someday breaking even. Getting them to live up to their potential has given scientists more than a few headaches in the years since they were discovered. Let’s see how much you know about these wonders of electromagnetism.

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