Understanding Band Theory: The Difference Between Conductors and Insulators

In summary, the question is why conductors have electrons at the fermi level gaining kinetic energy instead of potential energy, like the electrons in other bands when an insulator is placed in an applied field. The answer is that in conductors, electrons are trying to minimize their potential energy.
  • #1
Pdawgg
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My question is as follows: if you place an insulator into an applied field, the only thing that will happen is that the potential energy of each band will shift, according to the potential that it is in. Why is this exact same thing not what takes place in conductors? Why do the electrons at the fermi level gain kinetic energy instead of potential energy, like the electrons in the other bands?

This is a simple question and I know it will have an embarrassingly simple answer, but I am tired and cannot explain it or figure it out right now. Thoughts?
 
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  • #2
Since there's no way to delete: the answer is obvious. Of course the electrons will gain kinetic energy: they are trying to minimize their potential energy...
 

1. What is band theory?

Band theory is a concept in physics that explains the behavior of electrons in solids. It states that the electrons in a solid are arranged in energy levels, known as bands, and that the movement of electrons between these bands is what allows a material to conduct electricity.

2. How does band theory explain the difference between conductors, insulators, and semiconductors?

Band theory explains that the number and arrangement of energy bands in a material determine its electrical conductivity. Conductors have a partially filled valence band and a partially filled conduction band, allowing for easy movement of electrons. Insulators have a completely filled valence band and an empty conduction band, making it difficult for electrons to move. Semiconductors have a partially filled valence band and a partially filled conduction band, but the energy gap between the two bands is small, allowing for some movement of electrons under certain conditions.

3. What is the difference between valence band and conduction band?

The valence band is the highest energy band that is completely filled with electrons in a solid. These electrons are tightly bound to the atoms in the material and cannot move freely. The conduction band, on the other hand, is the band above the valence band that is partially filled or empty. Electrons in the conduction band are free to move and are responsible for the material's conductivity.

4. How do impurities and defects affect band theory and conduction?

Impurities and defects in a solid can create localized energy states within the band structure, which can affect the movement of electrons. These states can act as traps for electrons, reducing the material's conductivity. However, in certain cases, impurities can also introduce additional energy levels, creating more available states for electrons to move, thus increasing the material's conductivity.

5. How does temperature affect band theory and conduction?

As temperature increases, the atoms in a solid vibrate more, which can disrupt the regular crystal lattice structure. This leads to an increase in the number of energy states available for electrons to move, resulting in an increase in conductivity. However, at very high temperatures, the vibrations can become so strong that they can break the bonds between atoms, decreasing the material's conductivity.

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