----- Original Message ----- From: "Rick Regan" > But aren't R and V the only two of the three variables > that you can manipulate directly? No, not really. There is a current source in the EE lab that maintains a set current regardless of voltage or resistance (within reason). I think ordinary transistors do this to some extent also, as they are current amplifying devices. It just so happens that most people are more acquainted with measurements in voltage due to the use of batteries, wall warts, etc. A current source makes I an independent variable. Also there are some applications where R changes with I, which makes R the dependent variable! So in terms of which is the "proper" way to write it, I'd say it really doesn't matter. It's probably just easiest to avoid the fraction, so most people write E=IR. I think writing it I=V/R would be less confusing > to the novice. With the V=IR form, I've seen > descriptions like "if the current doubles the voltage doubles." Mathematically, yes, but it's not like you can > double the current independently of V and R. > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu