# Explaining Band theory and Momentum Space to laymen?

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1. Mar 22, 2015

### quarky2001

I didn't put this in the Education forum because I feel the level is probably too high.

I have a physics degree and an education degree, but due to my inability to tolerate students who simply don't care about learning, I became an electrician instead.

My colleagues and I were having a discussion about technical training, and the conversation drifted toward what really causes conduction to occur, and I piped up, having taken several semi-advanced solid state physics courses.

What I realized is, when I tried to explain conduction in simplified terms of k-space and band structure, it just sounded like the Bohr model, when in reality it's quite different. Any ideas how to effectively explain the concepts to someone with a rudimentary understanding of Ohm's law, resistivity, Kirchoff's rules, and basic trig?

2. Mar 23, 2015

### jfizzix

What to explain depends on what level of response they're looking for.

What makes a material conduct electricity?

Well, in order for electricity to flow in a wire, electrons must be able to flow in the wire.

In order for electrons to be able to flow in a wire, they can't be held too tightly by single atoms in the wire.

In metals, it just so happens that the outermost electrons in atoms of metals are loosely bound enough to flow from atom to atom.

Since these electrons can collide with the lattice of metal atoms (called ions without their outermost electrons), you get a kind of drag and loss of energy as the electrons flow (like beads in an African rainstick). This is what I could probably explain to a layperson about how electrical resistance works.

So why are some materials better conductors than others?
- Some atoms hold onto their electrons more loosely
- Some atoms share their electrons with others more readily
- Some atoms make bigger targets for collisions
- Some atoms have more electrons to spare (perhaps?).

I couldn't say much more than this (at a layperson level), as you almost certainly know more solid state physics than I do.

Last edited: Mar 23, 2015
3. Mar 24, 2015

### ZapperZ

Staff Emeritus
I must admit that I don't quite understand how you needed to use band structure and k-space to explain simple charge transport in a conductor. Why can't you just stick with the Drude model and invoke the free-electron gas? The concept of drift velocity and applying basic statistics get you Ohm's Law and most of the typical characteristics of charge transport in metals.

Zz.