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How do superconductors work? A physicist explains what it means to have resistance-free electricity


The modern world runs on electricity, and wires carry that electricity to every light, television, heating system, cell phone, and computer on the planet. Unfortunately average approx 5% of the energy generated in a coal or solar power plant is lost when the electricity is transported from the plant to its final destination. This amounts to one US$6 billion loss per year in the US alone.

Scientists have been for decades developing materials called superconductors that transfer electricity with almost 100% efficiency. I’m a physicist which investigates how superconductors work at the atomic level, how current flows at very low temperatures and how applications such as levitation can be realized. Recently, researchers have made significant progress in developing superconductors that can function at relatively normal temperatures and pressures.

To see why these recent developments are so exciting and what impact they could have on the world, it’s important to understand how superconducting materials work.

Most materials resist when electricity passes through them and heat up. Resistance is how filaments in a light bulb produce light.
Ulfbastel/Wikimedia Commons, CC BY-SA

A resistance-free material

A superconductor is any material that conducts electricity without offering any resistance to the flow of the electric current.

This resistance-free characteristic of superconductors is in stark contrast to standard conductors of electricity – such as copper or aluminum – that heat up when current passes through it. This is similar to sliding your hand quickly across a smooth, slippery surface as compared to sliding your hand across a rough rug. The rug generates more friction and therefore more heat. Electric toasters and old-fashioned light bulbs use resistance to produce heat and light, but resistance can play a role problems for electronics. Semiconductors have a resistance lower than that of conductors, but still higher than that of superconductors.

Superconducting materials repel magnetic fields, making it possible to levitate a magnet above a superconductor.

Another characteristic of superconductors is that they repel magnetic fields. You may have seen videos of the fascinating result of this effect: It’s possible to levitate magnets above a superconductor.

How do superconductors work?

All superconductors are made of materials that are electrically neutral — that is, their atoms contain negatively charged electrons surrounding a nucleus with an equal number of positively charged protons.

If you attach one end of a wire to something positively charged, and the other end to something negatively charged, the system will want to achieve equilibrium by moving electrons around. This causes the electrons in the wire to try to move through the material.

At normal temperatures, electrons move in somewhat erratic orbits. They are generally free to move through a thread, but occasionally they collide with the cores of the material. These collisions hinder the flow of electrons, create resistance and heat the material.

The nuclei of all atoms vibrate constantly. In a superconducting material, instead of fluttering around randomly, the moving electrons are passed from atom to atom in such a way that they stay in sync with the vibrating nuclei. This coordinated movement causes no collisions and therefore no resistance and no heat.

The colder a material gets, the more organized the movement of electrons and nuclei becomes. This is why existing superconductors only work extremely low temperatures.

A close-up of a computer chip.
Superconducting materials would allow engineers to fit many more circuits onto a single computer chip.
David Carron/Wikimedia Commons, CC BY-SA

Advantages for electronics

If scientists could develop a superconducting material at room temperature, wires and circuits in electronics would be much more efficient and produce much less heat. The benefits of this would be widespread.

If the wires used to carry electricity are replaced with superconducting materials, these new lines could be up to 1.5 meters high five times as much power more efficient than current cables.

The speed of computers is usually limited by the number of wires that can be packed into a single electrical circuit on a chip. The density of threads is often limited by residual heat. If engineers could use superconducting wires, they could fit many more wires into a circuit, leading to faster and cheaper electronics.

Finally, with superconductors at room temperature, magnetic levitation could be used all kinds of applicationsfrom trains to energy storage devices.

Of recent developments bringing exciting newsresearchers looking at the fundamental physics of high-temperature superconductivity as well as technologists waiting for new applications are paying attention.

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