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rp181

Thu Feb 28 2008, 04:07AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

dont think this falls in psuedo science, if it is, go ahead and lock it :)

i was wondering, with wireless power and such, if u had a big enough coil thats live and running, and u were standing in it, would you be electrocuted?

Since blood is conductive, if there was a single loop with a blood vessel, would electricity be induced into your body?

Shaun

Thu Feb 28 2008, 05:08AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Yes current would flow thru your blood, but the transformer coil would no doubt have hundreds or thousands of turns, and then your body would have only one turn, so only a few volts would be induced in your body. Then blood resistance would be relatively high, so very little current would flow.

The same thing would happen if you stuck your finger in an induction heater.

Wait, can a current be induced wirelessly in a solution, since now ions are flowing instead of electrons? If it can't then all the above is wrong I guess...

...

Thu Feb 28 2008, 06:30AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You body will probably not be hurt by eddy fields induced by a tesla coil. As Shaun pointed out, the amount of voltage induced across your body isn't really enough to hurt you.

You can however capacitively couple large currents from a coil to your body, and often you do not feel these currents because they are such a high frequency.

On interesting (and quite scary demo) is that if you are standing next to even a relatively small coil emitting a decent e-feild (my 500w sstc putting out 4" sparks exhibits this quite nicely) you can hold an LED with your right hand on one lead, and your left on the other, and the LED will glow

rp181

Thu Feb 28 2008, 01:27PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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lol, cool :)

i thought a humans internal resistance is very low, low enough to say, 2v to get through?

EDIT: This came to mind because in popular science, people were suggesting a giant electromagnet to deter cosmic radiaton on long trips into space. The thing would take several gigawatts of power O.o

Bjørn

Thu Feb 28 2008, 03:44PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

From our wiki:

Hand-to-foot resistance with wet and undamaged skin:
Skin resistance (hand) = 500 Î©
Internal resistance (hand-foot) = 400 Î©
Skin resistance (foot) = 500 Î©
TOTAL BODY RESISTANCE (sum) = 1400 Î©

2V will get through a very high resistance if the current is low enough.

Shaun

Thu Feb 28 2008, 07:39PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

I saw that article; I don't think it specifically discussed this part but an electromagnet would be DC, right? So there would be no harmful transformer effect. The intense magnetic field affecting diamagnetic water in the body would be a bigger concern with a huge electromagnet around people.

rp181

Thu Feb 28 2008, 07:43PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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with something that big, wouldnt it just be easier to use AC current, which might affect you. I dont think the diamagnetic water would be much of a problem, just makes you heart work harder, Excersising with out moving :)

Marko

Thu Feb 28 2008, 09:11PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Yeah, interesting thing to think about, look at this:

I'm not sure how far it goes in reality, but, if I had some really huge iron core, energized by low frequency for some >50V/turn, and hugged the core, or made a 'shorted turn' over the core some other means by my body, I could (theoretically) get electrocuted!

By completely wireless means I think it's pretty unlikely. If you had a small coil with really massive amount of reactive power going through it at high frequency, could you observe some induction-heating in the tissue? I don't know. But definitely not a shock.

I don't know whether significant fully-wireless shock is actually possible, but if I was to match for high body impedance I'd far rather use electric than magnetic field.

In order to create real shock frequency would have to be well >20kHz. Let's say 10khz.

The difficulty is to get the capacitive current actually doing anything before you just get an arc!

If you assume 30kV/cm breakdown voltage of air, have a metal plate which closes some 100cm^2 with your hand 1cm apart:

- capacitance would be about 8.85pF;
-impedance at 10kHz would be 1.8megaohms
-so max theoretical current would be 16 miliamps! If I did it right.

At 1Khz it would be only 1.6 miliamps but more feelable due to lower frequency.

If you used some dielectric material over the electrode it would increase the effect, but honestly I don't believe you could ever deliver a lethal shock that way far before just forming an arc.

Still interesting stuff to think about, like some SF pain-field torture device.

Marko

teslacoolguy

Sat Mar 01 2008, 04:21PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
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this kind of reminds me of that one future weapons episode that they made a long range painfield kind of device that made you feel like you had a horrible sunburn using magnetic energy but it has been so long since ive seen that show i cant remember exactly how they did it.

Shaun

Sat Mar 01 2008, 05:44PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

That was a millimeter-band infra-red transmitter that was on futureweapons; they can get away with not calling it a "microwave" device since millimeter and below on the EM spectrum is far-IR, but it essentially microwaves you a little bit. Cool, but nothing to do with transformers. Maybe that will be next...

Marko, I can just see someone hugging a huge humming transformer core (physically insulated from their body of course) and wondering why they get shocked.

But can the alternating magnetic field induce currents in a conductive electrolytic solution? I mean, say I have a small ferrite core energized by a copper primary at some frequency and 5V/turn. Then for a secondary I wrap 5 turns of vinyl tubing filled with salt water. Could I read 25VAC across this winding?

Current only flows in solutions because the ions are attracted to an oppositely charged metal (or maybe graphite) electrode. In a transformer, the alternating field affects the electrons in metal atoms, causing them to flow. Could it effect entire ions?

Even in a conductive arc channel, the gas atoms do not flow, their stripped-away electrons do. So I am wondering if a human body, with electrons incapable of flowing by themselves, is really capable of becoming a shorted turn in a transformer system...

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