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Re: skin effect
Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>
Hi Terry and all,
Not a bad guess! Overall, humans have a bulk resistivity of about 400
ohm-cm, varying between about 150 ohm-cm for blood, 285 ohm-cm for parallel
muscle fiber, to 2500 ohm-cm for fat. So, using 400 ohm-cm, skin depth at
200 kHz would be about 89 inches or about 2.3 meters. Unless you're large
enough to merit your own zip code, skin effect is pretty much nonexistent
for people and Tesla Coils.
-- Bert --
--
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Tesla list wrote:
>Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>Hi Ryan,
>Skin depth is proportional to 1 / SQRT(F). So just a wild guess and if
>the skin depth of people is 1 meter at say 200kHz.
>d = SQRT( 200000 / 3300000 ) x 1 = 0.26 meters or about 10 inches.
>I have seen RF burns at 13.56 MHz and those burns go straight down into
>the body as do 350kHz burns.
>Although "skin depth" works well for metallic conductors, "I" personally
>think it has no meaning for a very high resistance materials like people
>are made from.
>Also note that microwave ovens (~2000MHz) cook large chunks of meat on the
>inside too... Water blocks microwaves some, but skin depth seems to have
>no meaning there.
>For all practical purposes, you can assume the RF currents go right deep
>inside you. The nerves simply don't react to it. People have reported
>nerve problems if they "overdo it". The RF currents do seem to favor
>flowing in the more conductive nerves and blood vessels concentrating any
>damage to those structures.
>Cheers,
> Terry
>
>At 12:27 AM 5/7/2003 -0600, you wrote:
>
>>My small coil actually resonates at around 3.3 MHz, does anyone know if this
>>would be a high enough frequency to cause the current to run completely over
>>the skin?
>>
>>I have taken the streamers from my coil directly to my hand (without much
>>shock sensation), and I have also done this with a coil operating at around
>>1.7 MHz, with more shock sensation. Does the amount of current in the
>>streamers depend directly on the turns ratio of the coil?
>>
>>Ryan
>>
>>
>>
>>-----Original Message-----
>>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>>Sent: Tuesday, May 06, 2003 5:55 PM
>>To: tesla-at-pupman-dot-com
>>Subject: Re: Man inside sphere electrode (electrum)
>>
>>
>>Original poster: "Ben McMillen by way of Terry Fritz <teslalist-at-qwest-dot-net>"
>><spoonman534-at-yahoo-dot-com>
>>
>>Hi all,
>> I've heard that they do the same thing with a figure 8
>>shaped coil and induce currents in the brain.. supposedly
>>causing halucinations.. I have no idea what kind of
>>currents or energies are involved.. Some kid here at the
>>university wanted to try it with my 5400J can crusher.. I
>>told him he was crazy!
>>
>>Coiling In Pittsburgh
>>Ben McMillen
>>
>>--- Tesla list <tesla-at-pupman-dot-com> wrote:
>> > Original poster: "Finn Hammer by way of Terry Fritz
>> > <teslalist-at-qwest-dot-net>" <f-h-at-c.dk>
>> >
>> > guys!
>> >
>> > It is possible to induce electric current into the human
>> > body, it is
>> > done for therapeutic reasons, and the current induced
>> > appear to occeur
>> > in the nerves.
>> > http://www.magstim-dot-com
>> >
>> > I have seen one such machine at work, at the Electricity
>> > Museum, and a
>> > one turn coil in proximity of the 17 turns work coil
>> > revealed that the
>> > pulse length is 100µS, the current producing it is in the
>> > thousands of
>> > amperes, and the flux intensity is more than 2 Tesla.
>> >
>> > Funny to work with: Place the coil where the halo of a
>> > saint would be,
>> > fire the coil, and you get funny looking, involuntary jaw
>> > movements. One
>> > of the office secretaries bit her tongue!. What a laugh
>> > :-).
>> >
>> > It is a disk launcher, really.
>> >
>> > Cheers, Finn Hammer
>> >
>> >
>> >
>> > Tesla list skriver:
>> > >
>> > > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>> > >
>> > > Hi Rik,
>> > >
>> > > At 04:40 PM 5/5/2003 +0000, you wrote:
>> > >
>> > > >Hi all,
>> > > >web surfing i came across this
>> > > >http://www.lod-dot-org/teslacoils.html
>> > > >
>> > > >man sitting in a cage electrode on top of his large
>> > coil.
>> > > >He is safe from electric fields there (well known
>> > Faradey cage effect),but
>> > > >i was wondering what about magnetic fields.?
>> > > >I suspect part of magnetic field could enter hollow
>> > sphere and induce
>> > > >currents in man's body.
>> > > >How real is danger of that possibility?
>> > > >
>> > > >Rik
>> > >
>> > > The magnetic fields at the top of the coil are not
>> > that
>> > > extraordinary. Maybe 10's of amps. Greg had an
>> > electronic oscilloscope
>> > > with him that was not harmed. I would guess if people
>> > can stand the
>> > > magnetics of MRI machines, they can stand top of Tesla
>> > coils easily. The
>> > > currents in the coil could induce some voltage around
>> > one's body. But the
>> > > resistance of the body is so high the current would be
>> > nil.
>> > >
>> > > Cheers,
>> > >
>> > > Terry
>> >
>> >
>
>.