# ¿How much energy can I obtain if I do the inverse process?

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You know that the a fan (like the pc fan that cools the processor) needs a quantity of energy to work. The most usually are 12V to work Ok.

Some days ago, I have seen a video where a guy moves a fan to make energy. That guy used the help of a blowdryer to move the fan at a high speed. The video shows that moving the fan at high speed you can make power to run a device (in the video was a led). So, if you have a motor, you can have a generator if you inverse the process (you move the fan).

My question is, If the fan need 12V to work properly... How much energy can I obtain if I move the fan? I know that It depends of the speed that I move the fan, but I want to know what is the max power that can I obtain. Can I obtain the same 12V moving the fan? More? Less?

Thanks

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The 12V is the voltage, you also need to know the resitance fo the device to know the power:

$P=\frac {V^2} {R}$

From that you can get the power.

The voltage produced (and therefore the power) will be related to the rpm of the fan, the faster it goes the closer to the 12V you can get, if you get the same rpm as the fan produces then yes you will get 12V out.

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Thank man,

I thought that I can´t obtain the 12V again, but yes a very near power.

How can I determine the resistance?

And another question... I can get more than 12V if I can move the fan very quickly? or that power is the max that can I obtain?

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you might be able to use a multimeter to measure the resistance, or it might be writen on the motor.

As for getting more out it'll depend on the motor itself, there's quite a high chance the coils will just melt....

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Couple months ago I made an electromotor using strong rare earth magnets and a spheric copper wire in the middle. When I connect the wire into a battery (usually 7.2V because 12V give out smoke), the spherical wire start rotating very very fast. I'm sure your know why. Now I have tried to opposite too. Connect the wire into a bulb (small 1.5A) and rotate the wire by hand, and it works! It bulb lights! The faster you move it, the more intense is the light.

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What's a shperical wire?

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A wire shaped like a sphere (not completely though)!

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