When you are creating a generator what determines how much current is generated?

You don't generate current. You generate voltage, and the amount of current that

leaves the generator is determined by the devices that are designed to run with

that voltage, and draw their operating energy from your generator.

You choose the size of the materials used to construct your generator based on the

maximum amount of current you expect it to be asked to deliver by its users. But

the actual current at any moment will depend on how many people are using it for

their supply, and what kind of appliances they're operating.

If nobody is using power from your generator, or the output cables are disconnected

from it, then you can run it all you want and the current will be zero.

Before you decide on the final design and go out for bids to construct your generating

station, you might like to review the topics of voltage, current, power, and energy, and

get them straight in your mind.