Conventional and Electron Current Directions
One circulation described two ways. Switch between the conventional picture and the real electron picture and the four-cell table lights up to show which is which, inside the source as well as outside it — the half students most often get backwards.
How to use this simulation
- Press Conventional (+) to trace the direction every formula and meter assumes
- Press Electron (real) to trace what the carriers actually do
- Follow one complete loop and watch the table fill in for outside and inside the source
- Pause at the terminals to see where each description changes over
What to look for
- Outside the source the two arrows always point opposite ways
- Inside the source both descriptions reverse compared with the external circuit
- Conventional current runs from − to + inside the cell, which looks wrong until the table is read
- The current has the same magnitude everywhere in the loop under either description
- Ammeters and circuit formulae are all built on the conventional direction
The physics behind it
In the external circuit conventional current leaves the positive terminal, crosses the load and returns to the negative terminal, while electrons do exactly the reverse. Inside the source both reverse again: the EMF drives conventional current from the negative plate to the positive one, against the external direction, and electrons correspondingly travel from positive to negative inside. Direction is therefore never a property of the wire alone — it depends on which convention is in use and on which side of the terminals you are standing.