131211-1022 EST
ronaldrc:
You need a basic understanding of fundamentals. One fundamental is the "conservation of energy". See
http://en.wikipedia.org/wiki/Conservation_of_energy
Start at the thermal engine driving an alternator. Coal or some other fuel is used to provide the input energy to drive a steam engine or turbine. The connected generator or alternator is a load on the heat engine. Whatever, electrical loads are on the generator are indirectly a load on the original source of energy (coal or whatever).
If there is no current being drawn from the generator, then there is no electrical load, but the generator is producing some voltage. There is a load on the original source of energy in the form of friction and other losses in the system. A big part of the loss is in the conversion of heat power into mechanical power. Mostly in that only a portion of the input heat energy is converted to mechnical energy, and the rest is lost heat energy as heat.
If I have an AC generator, and fully electrically load it with high quality capacitors to the point of full rated current, then I have essentially no power load on the generator. But I will have maximum allowed power dissipation in the generator. The internal losses in the generator now require some additional and equal input energy from the heat source.
Next remove the capacitor load. Put a pure resistive load on the generator that draws the maximum rated current. You now have the same internal losses in the generator as with the capacitive load, and additionally the power being dissipated in the load resistor. Now the source of heat energy has to supply all of the load energy.
The only place I mentioned voltage was with reference to the fact that voltage is present without any load current on the generator.
You have already been told by others that you are confusing voltage with power or energy.
On an instantaneous basis power can be described by the equation:
p = v*i and energy is the integral (summation) of p*dt over some time period.
In p*dt p is the instantaneous power and dt is an infinitismal period of time.
Consider your car battery example. Once car batteries were a nominal 6 V. In the 1950s this changed over a few years to 12 V. Why?
First: lead-acid cells have a nominal voltage of 2 V, thus any battery will be made to have a nominal voltage of 2*N where N is an integer. Fewer cells used means fewer components and less assembly cost.
Second: 6 V was adequate to start early engines, and power the limited electrical equipment. Starting in the 1950s engines got bigger and compression ratios increased. This required more torque from the starter motor. Also the electrical load was increasing. Because of higher currents and high resistive losses the decision was made to double the nominal voltage. The loads were designed around the new voltage level. Soon we may go to 24 to 48 V.
The source voltage was determined by an overall determination of system requirements balanced by cost of manufacture. With the source voltage defined, then the load components were designed for that source voltage. Your oddball 9 V device was not designed for direct automotive use. Thus, you have to do a voltage conversion by some means. This can be a series pass regulator (power waste) or by a switching regulator or a motor generator. I have a PE103 dynamotor (dynamo?motor, first known use 1899) that I will sell you. 6 or 12 V input and about 500 V output by memory.
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