# Semiconductors & Superconductors: Definition & Properties

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• 0:04 What Is a Superconductor?
• 1:11 Applications of…
• 1:39 What Is a Semiconductor?
• 2:16 Applications of Semiconductors
• 2:51 Lesson Summary

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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Have you ever wondered how an MRI works or how cell phones are able to become more advanced? After completing this lesson, you'll be able to explain what semiconductors and superconductors are and give examples of how they are used.

## What Is a Superconductor?

A superconductor is a material that acts strangely when cooled down to a certain temperature. When these materials are at that one special temperature, which we call the critical temperature, they suddenly become perfect conductors. What do we mean by this? Well, it means that their resistance is zero. A current in a superconductor can keep flowing without any decay, forever.

For most materials, this critical temperature is so incredibly cold that it would take a long time for us to even be able to achieve it. The critical temperature usually between absolute zero and 10 Kelvin (or between -273 Celsius and -263 Celsius). However, in recent decades, we've discovered materials that act as superconductors at much higher temperatures, as high as 125 Kelvin (or -148 Celsius). This is still extremely cold, but much more easily achievable for real life applications since we can achieve these temperatures simply by using liquid nitrogen.

## Applications of Superconductors

Superconductors can be used to create powerful electromagnets, like those used in MRI scanners in hospitals. They can also be used to separate magnetic and non-magnetic materials.

The hope is that we will one day be able to use superconductors to create vehicles that use magnetism and levitation to propel themselves forward. We might also be able to use them to create more advanced forms of energy storage.

## What Is a Semiconductor?

A semiconductor is a material that has conductivity somewhere between that of a conductor and an insulator. In other words, they're not as conductive as metals, but more conductive than plastics and other insulators. Examples include silicon, germanium, and gallium arsenic.

We can vary how pure these substances are and use this to change the conductivity of the material at will. This way, we can fine tune the material to be exactly as conductive as we want it to be. The process of adding impurities is called doping.

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