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| From | ram@zedat.fu-berlin.de (Stefan Ram) |
| Newsgroups | comp.os.linux.misc |
| Subject | Re: Floppies - Actual Question |
| Date | 6 Oct 2025 10:29:47 GMT |
| Organization | Stefan Ram |
| Lines | 32 |
| Expires | 1 Jun 2026 11:59:58 GMT |
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Lawrence =?iso-8859-13?q?D=FFOliveiro?= <ldo@nz.invalid> wrote or quoted: >On Thu, 25 Sep 2025 13:04:59 +0200, Carlos E.R. wrote: >>At some point in the 80's, a friend at uni wanted to go home with his >>floppies kept safe (the train was electric). We told him to try wrapping >>in aluminum kitchen foil, or perhaps in a cookie tin box. I don't >> remember what he did exactly, but it worked. >“Faraday cage”. In a perfect conductor, inside the material itself (such as the cage walls), the electric field E is zero because free charges move to cancel any applied electric field. Faraday's law then implies that within the conductor, the magnetic field B cannot be changing with time. Changing magnetic fields induce currents (eddy currents). These induced currents generate opposing magnetic fields that cancel the time-varying components inside the conductor, effectively shielding against changing magnetic fields. But this does not imply zero magnetic field inside the conductor's hollow interior (the cage's interior space). Static fields do not induce currents because there is no changing magnetic flux within the conductor to generate an electromotive force. Consequently, these magnetic fields penetrate the cage interior unaffected. Also, real materials might not be perfect conductors. And it seems that, in practice, a Faraday cage can possibly protect to some extend against fast changing magnetic fields, but less against slowly changing magnetic fields.
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Re: Floppies - Actual Question Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-09-25 22:10 +0000
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-09-25 21:09 -0400
Re: Floppies - Actual Question ram@zedat.fu-berlin.de (Stefan Ram) - 2025-10-06 10:29 +0000
Re: Floppies - Actual Question Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-10-06 22:08 +0000
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-06 23:30 -0400
Re: Floppies - Actual Question Rich <rich@example.invalid> - 2025-10-07 15:16 +0000
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-08 02:34 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-08 01:05 -0400
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-08 10:58 +0200
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-08 11:06 +0100
Re: Floppies - Actual Question ram@zedat.fu-berlin.de (Stefan Ram) - 2025-10-08 12:10 +0000
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-08 14:14 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 02:44 -0400
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-09 21:10 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 21:36 -0400
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-10 09:54 +0100
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-11 01:57 -0400
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-10 13:49 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-11 02:29 -0400
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-11 14:32 +0200
Re: Floppies - Actual Question Joerg Walther <joerg.walther@magenta.de> - 2025-10-09 12:50 +0200
Re: Floppies - Actual Question "Carlos E.R." <robin_listas@es.invalid> - 2025-10-09 21:11 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 21:37 -0400
Re: Floppies - Actual Question Joerg Walther <joerg.walther@magenta.de> - 2025-10-10 11:19 +0200
Phone wallet "Carlos E.R." <robin_listas@es.invalid> - 2025-10-10 13:51 +0200
Re: Phone wallet c186282 <c186282@nnada.net> - 2025-10-11 02:30 -0400
Re: Phone wallet "Carlos E.R." <robin_listas@es.invalid> - 2025-10-11 14:32 +0200
Re: Phone wallet c186282 <c186282@nnada.net> - 2025-10-11 21:35 -0400
Re: Phone wallet "Carlos E.R." <robin_listas@es.invalid> - 2025-10-12 14:48 +0200
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 21:17 -0400
Re: Floppies - Actual Question Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-10-10 06:51 +0000
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-10 03:29 -0400
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-10 09:55 +0100
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-11 02:10 -0400
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-08 13:18 +0100
Re: Floppies - Actual Question Robert Riches <spamtrap42@jacob21819.net> - 2025-10-09 03:09 +0000
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 02:58 -0400
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-09 12:45 +0100
Re: Floppies - Actual Question Robert Riches <spamtrap42@jacob21819.net> - 2025-10-10 02:53 +0000
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 23:44 -0400
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 02:45 -0400
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-09 02:38 -0400
Re: Floppies - Actual Question Rich <rich@example.invalid> - 2025-10-09 15:16 +0000
Faraday cages (was: Re: Floppies - Actual Question) Nuno Silva <nunojsilva@invalid.invalid> - 2025-10-09 17:02 +0100
Re: Faraday cages Rich <rich@example.invalid> - 2025-10-09 18:48 +0000
Re: Faraday cages The Natural Philosopher <tnp@invalid.invalid> - 2025-10-10 09:49 +0100
Re: Floppies - Actual Question The Natural Philosopher <tnp@invalid.invalid> - 2025-10-10 09:47 +0100
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-11 01:05 -0400
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-08 01:52 -0400
Re: Floppies - Actual Question c186282 <c186282@nnada.net> - 2025-10-08 01:38 -0400
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