Does the length (resistivity) of an ethernet cable effect transfer speeds?

I'll be moving into a dorm room with an ethernet hookup pretty soon, and I don't know where the ethernet jack will be in relation to where I will put my computer. I could wait until the day I move into my dorm and find out, but I don't want to have to make a special trip to some store after I move into college. :/ I'd like to not worry about it and just buy a 10, 12 or 15 foot cord just to make sure I can reach the jack no matter what before I move, but....

I know that the resistance of a wire is proportional to the metal's resistivity, length and inversly proportional to the cross-sectional area. Since all ethernet cables have the same diameter and are made of the same material (...right?), I'm not worrying about those, only the length.

I'm assuming that resistivity effects transfer speeds since some high-speed users claim they can only attain "xkbps" because they are "y" miles or km away from the ISP's server. (Unless of course, they have a fiber optic connection.) Not to mention that the farther a dial-up person goes out into the country, the crappier their connection gets.

Basically, what I'm asking here is.... Will I get a slower speeds, even slightly slower, with say...a 10 or 12 foot ethernet cable instead of a 6 foot one? Or is the difference too negligable - even to downloading and networking software reporting downstream speeds - to even worry about?

Thanks.

How ya doing, buddy?