Will a Magnet-Powered Torch "Run Out"?

[wilkinsonjohn]

i'm sure we have all seen the little torches with a magnet inside that you shake to generate the required electricity to power the bulb... we were talking about them in the pub the other night and the following question came up...


my question is this, will the magnet ever "run out", and by that i guess I'm asking will the magnetic field around the magnet get weaker the more it is used or will it naturally get weaker over time regardless of how much the torch is used?

(the one thing we did learn is that beer makes you much smarter but you can never remember how smart you were the morning after)!

 

[MagnetDave]

No. The energy to light the bulb comes from your shaking the magnet. Analgously - gravity does not "run out" no matter how many times Sisyphus carries the stone up the hill.

 

[xx.jason.xx]

i'm sure we have all seen the little torches with a magnet inside that you shake to generate the required electricity to power the bulb... we were talking about them in the pub the other night and the following question came up...


my question is this, will the magnet ever "run out", and by that i guess I'm asking will the magnetic field around the magnet get weaker the more it is used or will it naturally get weaker over time regardless of how much the torch is used?

(the one thing we did learn is that beer makes you much smarter but you can never remember how smart you were the morning after)!

If you were using the magnet to perform the work, then yes, because the energy would be coming from the magnetic field, but since the energy is coming from you, the only limiting factor is you.