Let’s suppose that I attached magnets to the wheels of my car and wire coils next to them on the body of the car (let’s just suppose I did). Then as I drive around town I would create “free” electricity without changing the energy consumption of my car. This would seem to violate the laws of physics regarding the creation of energy without converting mass or energy. If this is a marketable idea I call dibbs on the patent.
Except you would change the energy consumption of your car. The resistance of the magnets would increase your fuel consumption.
Exactly. In fact, your car is already doing just this. Only instead of the magnets being on your wheels, they’re inside your alternator, along with the coil of wire. The more electrical energy being demanded, the greater the load on the alternator, and the more fuel is consumed. There are no free energy schemes. None will work. Ever.
Which is why using the air conditioner decreases your mileage, to use an illustration most will be familiar with.
Have you ever seen the hand crank light bulb apparatus? Same principle. When the light bulb is unconnected to the generator, turning the crank is easy as pie. Connect the terminals and it’s like turning a pencil sharpener.
During homecoming week at the University of Iowa we engineering students used to put on technical exhibits. One of the favorites for us was the hand powered electric generator. It consisted of a generator with a crank. The output was connected to an electric light bulb and also, way down at the other end of the lab to a shorting switch.
When a very husky guy and a little teeny coed came along we would ask if they wanted to generate some electricity. The coed would spin the crank and the light bulb would light up and everyone was happy. Then when the guy grabbed the crank, the shorting switch would be closed and he would, at our urging to try harder because after all the girl did it, almost bust a gut trying to turn the crank. The harder they pushed the harder the thing pushed back.
There’s also another way to generate “free” energy with your car. If you travel perpendiculary to the earth’s magnetic field (from east to west or west to east), then a small voltage difference is created between left and right side of the car. (depends on how fast you are traveling)
You can attach wires and use that potential difference to generate a small current.
Just like the OP’s suggestion, this will cause increased resistance to forward movement of the car. Albeit minimal - as minimal as the voltage across the car.
How to you actually make use of the current without having conductors that travel back to a single point (negating the effect)?
I don’t quite understand what you’re saying 
You move a conductor across the lines of the earth’s magnetic field - it generates a current, but the potential difference exists at opposite ends of the conductor - in order to make use of it, you have to connect your device power to opposite ends of the conductor - the wires that you use to do this also cut through the earth’s magnetic field, generating a current that cancels out the one you’re trying to use.
solar panels on every surface would get you free energy! probably enough to run your dome light, but if it were sunny, you wouldn’t need your dome light would you? :smack:
You would if you had covered every surface with solar panels, blocking out the natural light 
Although (as has often been noted) in cars with a reasonably low drag coefficient the normal alternative to air conditioning - open windows - may decrease mileage even more than AC.
“If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations - then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation - well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” – Sir Arthur Eddington
Free-energy schemes violate the first (energy conservation) or second (entropy is always increasing in the universe) laws of thermodynamics. (Another way of stating the second law is ‘there are no perfect engines’ that are more than 100% efficient.) Now, it is possible to make millions in a multi-level marketing scheme. It is possible to develop defined abdominal muscles by diet and exercise. It is possible to increase your self-confidence by listening to audio tapes. It possible to make a knife that can cut through a metal can, then cut tomatoes paper-thin. But it is not possible to violate the first and second laws of thermodynamics. If you have invented a device that seems to provide more energy than is put into it, either it is not working as you expect, or you are putting more energy into it than you think you are.
Running an extension cord from my next door neighbor’s outlet when he wasn’t looking worked pretty well.
Heh.
There is, however, a way to make the OP’s idea practical. Sometimes, after all, you want increased resistance to motion. If you set the system up so that the circuit is only closed when you step on the brake pedal, then you’ll convert some of your kinetic energy to useable electricity, rather than just wasting it as heat, as is the case for ordinary brakes.
This is called regenerative breaking, and is already included on every model of electric or hybrid vehicle. It’s one of the main reasons that hybrid cars are so superior to conventional vehicles (at least, in terms of fuel economy) in stop-and-go city driving.
But it’s still not free energy - there’s still loss as heat, in all parts of the electrical setup. But you’re certainly right that it’s a useful system nonetheless (and that it’s prior existence is the reason the OP isn’t a millionaire 
)
[nitpick] Not were I come from it isn’t. Tee hee. [/nitpick]
Well, if the regenerative system weren’t used the braking energy would all go up in heat so the part that is recovered is free, isn’t it?