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Old 07-26-09, 12:09 AM   #1
Ted Danson
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Explain to me why this won't work.

I was thinking about how to generate electricity from magnets. This is obviously a basic drawing but why couldn't you run a setup like this to gain electricity.
The magnets push off each other due to their polar fields and spin around on a fixed axis (purple point)
This fixed point is a rod that is connected to a generator.
The green arrow shows the direction the "fan" spins.

I don't exactly know how to explain how it works because it is late at night but I drew a picture to help

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Old 07-26-09, 12:58 AM   #2
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You'll generate electricity, but not as much as the energy you put into it. If you have to generate the wind from a fan, then forget it. You've got a fundamental thermodynamics problem.

If the wind is coming from some other energy source that you otherwise wouldn't have used, then yes, you can generate electricity. However, the magnets are exerting a force on each other in both directions. You'd do just as well with non-magnetic blades.
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Old 07-26-09, 01:04 AM   #3
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Oops... I was reading your drawing wrong. If you start at the right point, you might get the system moving a bit. But it will just wobble back and forth, since the acceleration in one direction radially is matched by the acceleration in the opposite direction in the mirror image position. (Yes, you can tilt the non-rotating magnet, but that merely changes where the equilibrium point is. It doesn't change the existence of such a point.) So there is nothing to be gained, and only frictional losses.

Furthermore, if you're generating electricity, then there is an additional resisting force since you're taking energy out of the system. Therefore, the system will rapidly settle at a stable position.

Ultimately, all this analysis can be simplified by simply realizing that no matter how cleverly you set up the system, you still can't get more energy out of it than is going into it.
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Old 07-26-09, 01:12 AM   #4
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it is an actually law, you have to put power in to get power out, it it's simplest form.

it may or may not be bernouli's principle, I need dinner.


what jchen is write I want to also add.
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Old 07-26-09, 01:19 AM   #5
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I don't understand how you are putting any work into it though. Magnets repell?
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Old 07-26-09, 01:37 AM   #6
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Read up on magnets on wikipedia, particular this section:
http://en.wikipedia.org/wiki/Magnet#Magnetization

The magnetic forces would cancel each other out and you would have a net-zero force.
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Old 07-26-09, 01:41 AM   #7
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it will get stuck between two magnets with a reason and just wobble. both magnets will repel in opposite directions with out a reason to repel from the magnet between them.

or someone to push it every so often, once again power input. If you were to put it in a power circle and make the outer magnet an electro-mag and have the power coming from the inner ring, you would still need need a way to make it pulse initially.

too late at night for diagrams
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Old 07-26-09, 01:42 AM   #8
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Quote:
Originally Posted by darksiderising View Post
Read up on magnets on wikipedia, particular this section:
http://en.wikipedia.org/wiki/Magnet#Magnetization

The magnetic forces would cancel each other out and you would have a net-zero force.
awesome, thanks great input
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Old 07-26-09, 01:43 AM   #9
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oh, and normal magnets over time a north side ran against a south side, is going to make the south side north. Or if you are really lucky, an east side messing every thing up.

Last edited by c0urt; 07-26-09 at 01:47 AM.
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Old 07-26-09, 02:05 AM   #10
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the real thermodynamics problem:
(1) you can't win
(2) you can't break even
(3) you can't get out of the game
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Old 07-26-09, 06:05 AM   #11
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I have a working perpetual enegy engine, but I'm not telling you about it!....Oops!
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Old 07-26-09, 03:53 PM   #12
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Originally Posted by Ted Danson View Post
I don't understand how you are putting any work into it though. Magnets repell?
Yes, but the moving magnet has to get into position to be repelled by the stationary magnet. The problem is that BEFORE it gets into that position, it will be in an ATTRACTION position. Imagine rotating your propeller anti-clockwise about 10-15 degrees. Before it can get into the repelling position, it will be pulled back by the stationary magnet and all rotation will stop.

What you've got drawn is very similar to a rotary piston airplane engine. Imagine each magnet as a piston pushing up and down in each cylinder. In order to keep the system going, you have to ADD energy to the system, such as an exploding air-fuel mixture.

In your system, you have to ADD more energy to break the rotating magnet away from the attraction position as each magnet spins past the stationary one. Where is this energy coming from?

Also you want to draw actual magnetic-field lines on the bar magnets. They aren't linear, but wrap around the ends.


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Old 07-26-09, 04:05 PM   #13
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When I started college, I had the same exact idea for an invention, expecting the repelling force of the magnets to keep this setup spinning indefinitely.

However, the same answers as posted above is what would happen. End result will be the contraption will spin a bit, vibrate for a bit, then stop because the repulsive force of one magnet cancels out the attractive force of another as it spins.
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Old 07-26-09, 04:32 PM   #14
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1st law of thermodynamics
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Old 07-26-09, 04:56 PM   #15
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I always wondered if there was a way to perpetually provide power to a battery running an electric car. It seems if you had a generator on each wheel and alternating battery supplies you could charge one battery while the other powers the car. Too good to be true?
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Old 07-26-09, 05:02 PM   #16
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I always wondered if there was a way to perpetually provide power to a battery running an electric car. It seems if you had a generator on each wheel and alternating battery supplies you could charge one battery while the other powers the car. Too good to be true?
Not a chance. Using one battery to charge another one is not going to gain you more usable energy than you started with. If it did, the world's energy problem would be trivial to solve.
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Old 07-26-09, 05:03 PM   #17
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I nominate you for the 'Coolest Poster on Foo' Ted. Keep up the good work. Now, if you engineer a couch that does the laundry and cooks, you'll have a friend for life! Start working on that now.

Couch
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Old 07-26-09, 05:12 PM   #18
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Take your gadget and weld onto a trianagular frame. Put your bike on the frame and pedal. Hook some wires up to your toaster.

Pedal real fast.
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Old 07-26-09, 05:12 PM   #19
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I always wondered if there was a way to perpetually provide power to a battery running an electric car. It seems if you had a generator on each wheel and alternating battery supplies you could charge one battery while the other powers the car. Too good to be true?
But what is providing the energy to turn the wheel that is charging?
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Old 07-26-09, 05:13 PM   #20
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I nominate you for the 'Coolest Poster on Foo' Ted. Keep up the good work. Now, if you engineer a couch that does the laundry and cooks, you'll have a friend for life! Start working on that now.

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Your priorities are all screwed up. You want to start with the basic essentials:

http://adventuresandbox.com/2008/08/...-couch-fridge/
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Old 07-26-09, 05:16 PM   #21
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Not a chance. Using one battery to charge another one is not going to gain you more usable energy than you started with. If it did, the world's energy problem would be trivial to solve.
Not using another battery to charge a battery, using the spinning wheel to charge a battery. Then when the battery is charged, switching over to it to run the car. Meanwhile, the other battery is running the car.
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Old 07-26-09, 05:18 PM   #22
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Not using another battery to charge a battery, using the spinning wheel to charge a battery. Then when the battery is charged, switching over to it to run the car. Meanwhile, the other battery ios running the car.
The battery is what ran the motor to spin the wheel. You're still ultimately charging one battery by taking energy from another battery.
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Old 07-26-09, 05:24 PM   #23
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The battery is what ran the motor to spin the wheel. You're still ultimately charging one battery by taking energy from another battery.
hmmm... why is this so difficult?
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Old 07-26-09, 05:25 PM   #24
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It simply can't be done.
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Old 07-26-09, 05:29 PM   #25
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It simply can't be done.
"can't be done" ??

That's not the spirit that got us where we are today. Maybe in another life.
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