I mean, I always used to fancy as a kid why can’t we use magnets to keep a fan going in circles? Why can”t we create a perpetual machine using magnets? Even if the magnets get worn out, we can still use them for considerable time. What is the science behind it that makes it impossible?
In: Engineering
As a child I once had an idea to put magnets facing all North polarity inwards on a sphere, using ridiculous amounts of superglue to hold them to the surface of the ball bearing. There were tiny gaps, where there would be an intense North polarity magnetic field, but for the most part this made a “bubble” you could feel on the sphere where it was primarily South magnetic field, about 2 inches above the surface of the magnets. The North areas were really weak polarity, the South areas were strong enough to hold the weight of the magnets glued together.
I then made a bowl lined with magnets, South polarity upwards. You see where this is going, right? I can balance the sphere above the bowl and spin it, and it should spin until air resistance stops it. I planned to remove air resistance from it, by putting it in a vacuum chamber with no air. If I could spin it fast enough to still be moving once the air was gone, it would never stop!
If that worked, the next step was obvious – I would wrap it in copper coils and generate an endless stream of electrical power. I had discovered the secret to perpetual motion, and was going to use it to generate electricity. Maybe not much at a time, but with enough of these and built better than my 10 year old hands could do with store bought magnets and superglue I could possibly make this work.
Then I happened to be on Wikipedia falling down a black hole of information, clicking link after link whenever I saw a new term to learn about, you know, the thing normal people do with Tumblr…
Anyways, long story short Lorentz Force is what you’re looking for. When you move the magnet near enough to a wire to generate electricity you’ll also generate *heat*. That lost energy produces a backwash effect – the energy in the copper is going slower than the magnet is spinning because it lost energy, and electricity in a wire generates a magnetic field. The magnetic field allows the wire to affect the spinning magnet, and since the electricity in the wire is slower it drags the magnet to a stop eventually.
So now I had a brand new problem – I could, in theory, make a perfect magnet and perfect base, put them in a perfect vacuum and make it spin forever. Here is where I’m permanently stuck – no matter where I go from here, *I can never extract more energy from the magnet than I initially put into it*. It will always slow down at the same rate or faster than the work being done by the electricity it generates.
It’s a bit long winded, and perhaps not quite ELI5, but I hope this helps add a layer of fun information to what others are saying here.
Latest Answers