|MadSci Network: Physics|
We have to keep clear macroscopic stuff (like electric circuits, where microscopic stuff works together so you can look at anything that happens in a simple way). For example, the current in a cylinder of copper is the result of an electric field acting on electrons free to move in this field. 99.99 percent of the time, this field is the result of a single externally applied voltage. The "current" is the result of a "current density" at any point in the cross-section added up (in calculus, we call this "integration") over the total cross-section area. The current density is caused at every microscopic point by the electric field acting on a mobile electron. Because the current density across the cross-section is constant, we just multply by the cross-section area to get current in amperes. Then we say the voltage across the whole cylinder times the current through the whole cylinder equals the power dissipated in the cylinder. Introducing another electric field complicates everything. Here's my recommendation. Try to learn how a solar battery works. This device uses phenomena you suggest might be there. A solar battery has a PN junction which automatically creates an electric field external to all outside influences. Light particles (photons) landing on the junction create charge carriers that are moved by the electric field out of the junction. Try http://science.howstuffworks.com/solar-cell.htm -- the wonderful site that
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