Superconductors

A superconductor.

Actually, I’ll be writing about superconductivity today, but superconductors made a better title, and also allowed me to use a clever graphic—lest we forget that these blogs are mostly about keeping me amused.

First, let’s have a couple demonstrations showing what superconductivity is all about.

Demonstration 1. Wave your hand about in the air as rapidly as you can. Now, move your hand just as rapidly, but keeping your palm in firm contact with the surface of a carpet. (Hey, I said firm contact.)

Okay, don’t be bleeding all over the carpet. So, do you feel the heat on your palm? That heat is caused by friction with the surface of the carpet as it resists the movement of your hand, what one might call (and I am calling) resistance.

Demonstration 2. For this demonstration you will need your mother’s permission: pop a slice of bread in your toaster (an English muffin would be better). Now crank that handle down. (It’s plugged in, right?) Hold your horses, give it a few seconds.

Image**

Now very carefully—don’t get too close—look down into the toaster slot. (If your eyebrows are smoldering, you’re too close.) See those glowing wires aligned on either side of the muffin? Those wires are made of a metal alloy designed to resist the flow of electricity. That resistance to the electricity causes them to heat up, glow red and yellow, and hence the delicious carmelization of the surface of the English muffin.

Now pop out that muffin, slather on a generous portion of margarine or butter (see how it puddles deliciously in all the nooks and crannies?), add a healthy dollop of jam, jelly or honey, and enjoy. In quantum mechanics, this is referred to as a snack.

The wires in the toaster conduct electricity. (Starting to see where we’re headed, eh?) They’re just designed to conduct it poorly, so there is resistance, which causes heat, with some light as a byproduct. The same method is used to create light in an incandescent light bulb—which is also why they’re inefficient, because so much of the electricity ends up creating heat rather than light.

On the other hand, most electric lines or wires are designed to conduct electricity with as little resistance as possible, from the cord connecting your computer to your house current to the high voltage transmission lines that carry electricity from generating facilities to distribution and transformer stations throughout the country.

There are two problems, however. First, all metal wires—and there really aren’t any other kind in general use at present—have some resistance to electric flow. Secondly, the lower the voltage of that flow, the more susceptible it is to resistance.

So, to carry electricity over distances, power companies raise the voltage to very high—and more dangerous—levels. Even so, it’s estimated that upward of 5% of the power generated in this country is lost to resistance before it even makes it to a consumer’s electric meter. To transmit power at preferred lower voltages would result in exponentially higher losses.

At the opposite end of the spectrum, the flow of electricity in the ever-smaller circuits of computers causes problems of speed, proximity and heat that have our current technologies reaching their theoretical limits.

What physicists have sought, ever since electricity became more than just a conjurer’s trick, was a means to conduct electricity at low voltages without loss to resistance.

Image: American Superconductor

In 1911, Dutch physicist (and Noble laureate) Heike Kamerlingh Onnes, who studied how materials behaved at very low temperatures, discovered that, when super-cooled—and by super-cooled I mean temperatures very close to absolute zero, -459.67 degrees Fahrenheit—some materials lost all resistance to electrical conductivity. Hence the term, superconductors.

In theory, if one put an electrical current into a closed loop of superconductive material, the electrical current would move unimpeded, without any loss, through that loop indefinitely.

Image: ItsSaulConnected.com

The problem remains, even 100 years later, that materials still must be super-cooled to become superconductors, an expensive and impractical consideration for general use. But research has been developing materials that can superconduct at slightly warmer temperatures and the holy grail is that material that can superconduct within ambient temperatures.

And I wouldn’t mind finding some way to toast my English muffins faster.

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