# Why don't superconductors emit a lot of heat?

• osnarf
In summary, a superconducting electromagnet does not produce heat. This is because the rate of heat energy being dissipated = voltage^2/resistance. Resistance is not exactly zero, but it's very close, so it stands to reason that this low of a resistance should produce a ton of heat.
osnarf
Hi everyone, just a quick question.

I just heard someone say a superconducting electromagnet does not produce heat, which I find very strange, since it seems that, since rate of heat energy being dissipated = voltage^2/resistance. Taking the limit as resistance goes to 0, with voltage held constant, power approaches infinity. I remember reading that resistance is not exactly zero, but it's very close, so it stands to reason that this low of a resistance should produce a ton of heat. Hence, confusion.

I am not intimately familiar with superconducting magnet technology, but I can say this: super conductors have zero electrical resistance. Not a small amount, not practically zero, but exactly zero. It's some weird quantum mechanical effect that I can't remember the name of, but there is literally 0 ohms resistance in a superconducting wire. That's why they are such a huge deal.

If your intuition can't grasp how it can be exactly zero, don't worry. Quantum mechanics is beyond any form of human intuition.

osnarf said:
Hi everyone, just a quick question.

I just heard someone say a superconducting electromagnet does not produce heat, which I find very strange, since it seems that, since rate of heat energy being dissipated = voltage^2/resistance. Taking the limit as resistance goes to 0, with voltage held constant, power approaches infinity. I remember reading that resistance is not exactly zero, but it's very close, so it stands to reason that this low of a resistance should produce a ton of heat. Hence, confusion.

The heat produced is also zero because you can't produce a voltage across zero resistance without infinite current.

A better formula would be Power = I2 times R
So whatever current you do send through the superconductor is multiplied by zero to give you zero power.

This comes up on this forum every so often, but the very definition of a superconductor is that it has zero resistance. If you get a current circulating around in one (pumping via Lenz's Law) it'll keep on going forever (or until the superconductor warms up, stops becoming a superconductor, and blows up / melts down instead):

Okay that makes sense, I thought it was near zero, not exactly. Thanks for clearing it up.

## 1. Why don't superconductors emit a lot of heat?

Superconductors are materials that have zero electrical resistance at very low temperatures. This means that when an electrical current flows through them, there is no energy lost as heat. The absence of resistance also means that there is no energy wasted in the form of heat, making superconductors extremely efficient at conducting electricity.

## 2. What causes superconductors to emit very little heat?

The lack of heat production in superconductors is due to the phenomenon known as superconductivity. In a superconductor, the electrons are able to move through the material without any resistance, which means they do not collide with the atoms in the material. Without these collisions, there is no energy lost as heat.

## 3. Can superconductors emit any heat at all?

Superconductors do emit a small amount of heat, but it is significantly less than normal conductors. This is because even though there is no resistance, there are still some imperfections in the material that can cause a small amount of energy to be lost as heat. However, this heat production is so minimal that it is almost negligible.

## 4. Why do superconductors only emit heat at low temperatures?

Superconductivity only occurs at very low temperatures, typically below -200 degrees Celsius. At higher temperatures, the electrons in the material are more likely to collide with the atoms, leading to resistance and heat production. Therefore, in order for a material to exhibit superconductivity, it must be kept at very low temperatures.

## 5. Are there any practical applications for the low heat emission of superconductors?

Yes, the low heat emission of superconductors has many practical applications. One of the main applications is in high-speed transportation systems such as maglev trains, which use superconducting magnets to levitate and propel the train at high speeds with minimal energy loss. Superconductors are also used in medical imaging technologies such as MRI machines, which require high magnetic fields and benefit from the low heat emission of superconducting magnets.

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