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This should put this argument to rest, as this was taken out of one of my old textbooks. So, here it is:

There are two types of generators, AC and DC. Another name for an AC generator is ALTERNATOR, since it alternates the current, hence the AC.

"In a generator (AC or DC), the situation is the reverse of that for a motor. The mechanical turning (via engine belt) of the armature(coil) induces an emf (Electro magnetic field) in the loops(stator), which is what we call output. If the generator is NOT connected to an external circuit (i.e. your headlights), the emf exists at the terminals ONLY, and no current flows. In this case, it takes LITTLE effort to turn the armature.

BUT, if the generator IS connected to a device that draws current, then a current flows in the coils of the armature. Because this current-carrying coil is IN A MAGNETIC FIELD(it is experiencing magnetic flux), there WILL BE A TORQUE EXERTED ON IT (just the reverse of a motor), and this torque OPPOSES the motion. This is called a COUNTER TORQUE. The GREATER the load--that is, the more current that is drawn--the greater will be the counter torque. Hence, the external applied torque will have to be greater to keep the generator turning. This of course makes sense from the conservation-of-energy-principle (remember that???). MORE mechanical energy INPUT is needed to produce more electrical-energy OUTPUT."

If the generator(alternator) didn't require an increase in applied rotational force, we would be violating the conservation of energy principle, and would have discovered a form of perpetual energy.

End of discussion.

Keep in mind though, we are talking about small amounts of force, so it is a moot point, but a valid one, none the less.
 

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I agree with Dave-lets end this!

! He read the book...
 

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<b>my point</b>

I think I didn't correctly state what the whole point of the first alternator post was. The assumption made when I stated that the alternator spins freely was the intitial loss in hp that results from the spinning of the alternator is not considered. The original post was saying that there was significant loss in hp from generating the extra amps. Let us just assume that the initial power loss from spinning alternator producing 40amps is 1HP. We cannot just say that 40amps is why we lose 1hp. This is also a direct result of bearing friction in the alternator, belt friction to drive the alternator, energy discipated as heat, innefeciences with the alternator, etc. Now the EMF's that make up this 1hp loss are only a fraction of the equation. To further increase from 40amps to 60 amps is neglible in overall hp gains. Now once you reach the potential of the alternator "amp" output this becomes more noticable. We now need to consider the requirements of the ignition system that can become affected. A good analogy would be the MSD ignition box. By increasing the amount of spark to the plugs, we can increase the hp through better fuel combustion. Would it not be safe to say that with a decrease in the amount of volts/ams need by the ignition system that we will lessen the magnitude of the spark, thereby lessening the power potential of the motor. Let me make a long story short. I know about EMF and that torque is required to produce the output from the alternator, but less than 1% or so of total power is nothing.
 

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I'M BORED

Lets talk about tire or wind drag now. Or how about how much extra horsepower a beer gut needs to move it from 0 - 60. I lost 20 lbs and cut my time .05 seconds!
 
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