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I am thinking about building a simple electrical generator, and I am trying to make sure I clearly understand the theory and expected results before starting the project. I have two basic questions:

1) How do I calculate the generators maximum current and wattage, if i know the induced emf?

2) How is this generators output power related / limited by the input mechanical power?

At the moment the concept is a simple renewable energy source which is the prime mover, acting to drive a magnet up and down a cylindrical coil, with N turns. So I believe this should be a simple classical problem.

I am clear that the voltage induced is calculated by Faraday's law - and I am comfortable with how this would be develop. Based on my initial setup of 200 turns, 6000gauss magnet, a cylinder of radius 4cm and a magnet travel speed of 0.25m/s i get a voltage of ε = 4.824V

I am conformtable with Ohms law, however, where i am confused is how I calculate the actual current and generators maximum wattage. Suppose for arguments sake I have a 1 Ohm load resistor, and neglect the impedance of the generator coil - I think that the induced current would be :

4.824V / 1 Ohm = 4.824 Watts

But if I reduced the loads resistance to say 0.5 Ohm, i get:

4.824 / 0.5 Ohm = 9.648 Watts

Similarily if I put a load resistance of 0.01 Ohm, i get a figure of 482Watts

So I am unclear as to how the generator can seemingly produce more power, by reducing the load resistance. Surely the actual power produced is limited by the amount of input energy coming in from the magnet?

Is there a way to calculate the maximum theoretical output and if so, can someone provide some guidance?

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# Calculating actual power (wattage) created by a simple generator

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