Charge Carriers in Different Materials
Four conductors side by side — a metal, an electrolyte, a semiconductor and an ionised gas — each with a different set of carriers moving inside it. Whatever is actually carrying the charge, the conventional current through all four comes out pointing the same way.
How to use this simulation
- Press Metal to see conduction by free electrons alone
- Press Electrolytic solution to watch positive and negative ions separate
- Press Semiconductor to follow electrons and holes moving in opposite directions
- Press Ionised gas to see light electrons and heavy positive ions carrying the same current
What to look for
- The conventional current arrow points the same way in all four materials
- In the electrolyte both ion species move, and both add to the current rather than cancelling
- Holes in the semiconductor drift with the field while its electrons drift against it
- Electrons in the ionised gas move far faster than the positive ions, but both carry charge across
- Only the metal has a single kind of carrier — the other three all carry current two ways at once
The physics behind it
A metal conducts through free electrons alone, all negative and all drifting one way. An electrolyte carries positive and negative ions travelling in opposite directions, and both contribute to the same conventional current. A semiconductor adds holes, which behave as mobile positive carriers alongside its electrons. An ionised gas carries electrons and positive ions together. In every case the conventional direction is fixed by the field, not by the carrier: a negative carrier moving one way counts identically to a positive carrier moving the other.