Sometimes while solving problems Kirchoff's Voltage Law, there comes a resistor placed in such a position that in one of the loops the potential across that resistor is actually taken positive (which shows an increase). My question is how can this be possible, not that I doubt it but i need an explanation that explains it on the electron level. For example I understand that electrons normally loose energy due to work against the atoms inside a resistor. I need an explanation of how electrons gain potential (or energy) as they move across a resistor in the opposite direction of normal current flow. A microscopic (electron-scopic) scale explanation would be appreciated.
The one thing you can take for sure is that whichever is the direction of the voltage drop, is the direction of the current. So if a resistor is placed so the voltage goes up, instead of down, it means the current is going to go the other way. It's a lot like elevation and the flow of water in a river. The electrons will be pushed in the direction of downward voltage drop.