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Some physics problems? (Posted on 2006-04-16) Difficulty: 5 of 5
This was a problem I troubled myself with when the Physics teacher taught electromagnetism.

Assuming that we can create a gigantic alternating current generator in space, rotating a gigantic circular magnet around a gigantic wire coil to induce an alternating current, will we not get infinite energy and defeat the law of conservation of energy?

As the whole set up is in space, there is no friction whatsoever between the components though the wire naturally has some resistance. The wire's induced magnetic field can oppose the rotation of the magnet, but this can be easily be counteracted by routing a bit of energy from an external circuit to the magnet. As the magnet is circular the gravitational attraction between the circular magnet and coils cancels out. The power from the wire coil will then be connected to a device which will transmit the energy to earth via an electromagnetic wave.

The only energy inputs are that to keep the ring rotating and the initial energy input to put the setup in space. The output in energy is theoretically infinite.

SOMETHING is wrong with this argument that I later discovered myself. The Physics teacher was unable to detect it and walked away quite puzzled. Can you guys find out why this would never work?

See The Solution Submitted by Jack Lim    
Rating: 3.5000 (2 votes)

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One more thing... | Comment 10 of 13 |

On this device, as conceived, the electrical energy produced is "beamed" to the earth.  Thus, it has no wires to connect it to the outside owrld, or get tangled.  Then, it would not matter if the device was somehow "held" in place - in fact it wouldn't have to be.

If the gneerator was in equalibrium, and was then slowly and smoothly spun up to speed, it would still work.  The rotor would spin the opposite direction from the magnets (coservation of momentum), but that doesn't matter, becasue it is the realtive motion between the coils and the magnetics that counts ingenerating current.  In this case, both sides would spin like two conneted but opposing gyroscopes, reaching rotational equilibrium when the source ot he input torque energy equaled the electrical output energy.  And, since only internal torques are invoveld, the device would theoretically just spin in space, because it would experience not external force to move it.

Again, being in space deos not really matter to this result.  On earth, it is just really inconvenient to try to hold on to a counter ratationg device, so we fix one side to a frame.

  Posted by Kenny M on 2006-04-18 18:29:46
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