/diy/ - Do It Yourself

Looking at getting an air compressor, found 3 on amazon and i can't decide which one I like. All 3 have 4.5 stars and all are prime elegable (I live in Alaska so this is important).
It will be used for light garage work, so airing tires, blowing particulate off of stuff, eventually powering some light duty air impact/wrench/hammer/etc and other stuff like that. Nothing super demanding or needing to be run for minutes at a time with no stopping.

http://www.amazon.com/gp/product/B003S81T7O
Campbell Hausfeld HL540100AV $200
8 gallon rolling tank
125 psi
1.3 HP oiled
4.5cfm @40psi, 3.7cfm @90psi
>largest capacity, oiled so quieter, highest cfm

http://www.amazon.com/gp/product/B000N5UHK0
PORTER-CABLE C2002-WK $140
6 gallon pancake tank
150 psi
Unknown oilless
3.5cfm @40psi??, 2.6cfm @90psi
>Includes hose and accessories, cheapest, probably most compact

http://www.amazon.com/gp/product/B00NOSCDPA
California Air Tools 5510SE$190
5.5 gallon rolling tank
120 psi
1 HP oilless
3.1CFM @40PSI, 2.2CFM @90PSI
>dual piston, only 60db when running, underclocked due to dual pistons for longevity and power savings (only 8.5 amps)

help me understand /ohm/... i dont understand the concept of a device drawing current vs the source just sending all of its power at once.
how come, say, you stick a fork or wire in socket and you trip the breaker and fuck shit up but if you hook up something like a microwave transformer (that is just 100 or so turns of copper wire) everything works just fine? its more or less the same shit just with more resistance right?
or how like an electronic device can have a couple batteries in it that can max out at 5 amps output or so, but only send the current the device asks for instead of just frying it.
i just cant wrap my noodle around how this works.