I = ampère = amount of electron flow
R stands for "resistance"
U (I'm european) stands for "unterscheid" (german for difference)
What does "I" stand for, or in other words, what does "I" abbreviate?

"I" = capital i

 

Did you try google?

I stands for Intensivität, german for Intensity.

 

Dunno. When I first learnt physics we were taught P=mf. That is force = mass times acceleration. Go figure.