If you spin this generator at 1,000 rpm, it can produce 1 amp at 6 volts."WHY 6 VOLTS.ANY FORMULA?

Question

In an electrical circuit, the number of electrons that are moving is called the amperage or the current, and it is measured in amps. The "pressure" pushing the electrons along is called the voltage and is measured in volts. So you might hear someone say, "If you spin this generator at 1,000 rpm, it can produce 1 amp at 6 volts." One amp is the number of electrons moving (1 amp physically means that 6.24 x 1018 electrons move through a wire every second), and the voltage is the amount of pressure behind those electrons

Answer 1

No, they picked an arbitrary number.

There is a relationship between rpm and volts, but it is only useful to determine the voltage of that generator at different rpms.

Answer 2

For a generator, the voltage is a fixed function of the RPM you turn the rotor.

A motor of generator will have a "kV" value. For a motor with a kV of 200, for every volt applied it will TRY to spin 200 rpm.

If a generator has a kV of 200, then for every 200 rpm you turn it, it will put out 1 volt.

By changing the winding pattern or magnet strength you will change the kV of the generator.

So for your generator that puts out 6 volts at 1000 rpm, it will have a kV of 166.66 rpm/v

The rating would also indicate its recommended operating RPM. Spinning it faster could increase the voltage, but can damage the generator. The bearings or the rotor may not be able to handle a higher speed. The amperage rating is also important because excess current will overheat the generator and ruin it.

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An automotive "Alternator" is a different type machine, with automaticly varying magnetic field to keep the voltage within a narrow range despite a wide range of rpm.