1. I have a car that has some electrical/electronic weirdness; the basic issue is apparently parasitic draw of about 2.5amps @ 12v. When I connect the (problematic) component the chassis ground (connected to battery ground) what I observe is that the battery chassis jumps from 0v to something like 1.1v and I see the 2.5 amp draw. I connected the related chassis ground connection directly to battery ground and saw the amp draw go to 0.5 amps. This tells me there is some sort of grounding weirdness. My basic question is what kinds of things could/would cause chassis ground and battery ground voltage disparity? I imagine that a bad diode would let current go back into a circuit creating a potential loop where the voltage never got back to battery ground. Ideas? 2. Unrelated to the first question. V = I/R is Ohm's law but if you take a 12w fluorescent high efficiency bulb and run 120v into it the math says there's a 1200 ohm resistor sitting in the bulb given by 120v * (120v/1200ohms = 0.10 amps) = 120v*0.10 amps. Likewise you might have a 100w bulb that would have a smaller resistance. My question is does wattage take into account heat generated at the resistor(s) in the circuit or just I*V? If wattage doesn't define energy but power then what formula defines total energy consumed as opposed to power? Forum looks great. Sorry about undescriptive title.