So suppose you had a big, dense, heavy magnet that we got into orbit. In its path of orbit would be a tube of copper wire running all the way around the planet. So it would be orbiting the planet, inside this tube of copper wire. If we were to draw electricity from that wire, would gravity keep the magnet moving, therefore providing more electricity? Or would it lose kinetic energy and fall? And would it make a difference if it were on a perfectly spherical planet, rather than earth, which isn't a perfect sphere? I'm pretty sure the Law of Conservation of Energy prevents this, but I'm still curious. Thanks in advance!
$\begingroup$
$\endgroup$
3
-
1$\begingroup$ By a "tube of copper wire", do you mean a long solenoid that is then bent around into a torus? $\endgroup$– Michael SeifertCommented Mar 3, 2021 at 14:54
-
1$\begingroup$ Related, but using the Earth's magnetic field: physics.stackexchange.com/q/1121/123208 Also, en.wikipedia.org/wiki/Electrodynamic_tether $\endgroup$– PM 2RingCommented Mar 3, 2021 at 14:56
-
$\begingroup$ @MichaelSeifert Yes. $\endgroup$– Blue HerringCommented Mar 4, 2021 at 0:24
Add a comment
|
1 Answer
$\begingroup$
$\endgroup$
If you had a copper tube circling the earth with a vacuum inside, one might inject an object with an orbital speed that would also circle the earth. If the object were a magnet, it would induce pulses of current (as it passed a given location) which would circle the tube tangentially. These would dissipate power to the resistance of the copper, and would also generate magnetic fields which would decrease the speed of the magnet. The rate of loss of kinetic energy would match the power delivered to the currents.
