I remember stories about people who would run wires bewtween power poles.
The wires were close to the conductors themselves. The current running in
the conductors of course have a magnetic field around them and they cut
through the wires strung beneath them. The result was that power was stolen
from the power company.

I remember having a shortwave antenna wire running from my 3rd floor
apartment window across a telephone wire in front of my apartment window to
a light pole on a bridge near the building. I tuned in longwave frequencies
and was amazed to hear an FM transmission . It turns out that the local
security company was monitoring peoples' homes for intruders with listening
equipment inside their clients' homes and transmitting the signal over the
phone lines to their offices downtown. The magnetic field genrated by the
transit of the signal had sufficient current that it induced a signal
corresponding to theirs into my antenna line which was within several feet
of the telephone wire. Since it was FM and I had no FM mode on the receiver,
it was not a clearly readable signal, but if I tuned a bit off the main
frequency, I could just make out everything going on . I don't think any
current ambient in the environment would be dangerous unless it was actually
strong enough to be ionizing. I have seen photographs of people standing
next to transmitting towers holding fluorescent bulbs in their hands. the
bulbs were grounded and emitted a steady bright light.

In order to sheild yourself from EMF, it would be necessary to have several
feet of earth between you and the world and there would have to be some sort
of sheilding metal screen or a solid metal sheet inside it. Keep in mind as
well, that the magnetic field of the earth, the sun and in the space around
us associated with the galaxy also have an impact of some sort. For the most
part, none of that is of any consequence. We are sheilded from cosmic EMF by
the ionosphere and our earth's magnetic field, but it is not constant.
Certainly a percentage of cancers in a year are the result of radiation that
penetrates the atmosphere and the magnetic field of the earth. There are
thunderstorms on earth so powerful as to produce X-Rays. Clearly the
universe is an interesting place S.



"brun" wrote in message
...
cynical grin Careful, the oil lobby might come for you now.


"Dan Shanefield" wrote in message
om...
I would like to call your attention to an article in the current (Feb.
'04) issue of Nuts & Volts magazine, page 40, entitled "Harvesting
Electricity From The Environment." It describes an easy experiment
that produces some attention-getting (as well as educational) results,
and your teacher clients might be interested in it. Copies are for
sale at Barnes & Noble and at Borders magazine racks, or if you click
on the website, "back issues" can be ordered. The graphics for the
article can be clicked on to enlarge it, at
http://www.nutsvolts.com/toc_Pages/feb04toc.htm

I wrote the article, and a summary of it appears below (not
copyrighted), but much more is communicated by the article itself.

Best wishes, Dan Shanefield, Princeton, NJ, retired sci. prof.,
Rutgers U.
http://homepage.mac.com/shanefield/Resume1.html

------------------------------------------------------------
Easy Demo of EMFs by Dan Shanefield

(This is an uncopyrighted summary of my article in Nuts & Volts
magazine, Feb. 2004,page 40 --- see
http://www.nutsvolts.com/toc_Pages/feb04toc.htm .)

With cell phones, wi-fi, and microwave heating becoming
commonplace, the electromagnetic fields ("EMFs") going through all of
us are beginning to get scary. You can see for yourself by doing an
easy experiment. Just run a 15 foot wire (an extension cord will do)
out along the floor of your building. This will be your antenna.
Outside, pound a metal rod (a curtain rod will do) into the ground,
and run a wire from that in through an open window (thin enameled
magnet wire will do). Now hook up a voltmeter with a high input
impedance (any modern digital multimeter will do) to measure the
voltage between one end of your antenna wire and the grounding rod.

You are probably expecting to see a few microvolts, as I was. But
I saw 3 volts of ac. (On an oscilloscope, it's mostly 60 and 120 Hz
noise, but with lots of higher frequency "hash" riding on top of it.)
Putting the antenna outside in the back yard, horizontally draped over
beach chairs, I only got about 100 millivolts, but near a telephone
pole and power line in the front yard, there was at least a whole
volt.

Putting a rectifier diode in series, I charged up a 1,000 mfd
capacitor with that dc for about an hour, inside my house. It got up
to 5 volts, so I attached a tiny tungsten incandescent bulb that will
run on as little as 25 ma (Radio Shack cat. no. 272-1139). It flashed
briefly but quite visibly.

(Note: there are lots more easy experiments and explanations in the
Nuts & Volts article.)

Other writers have also worried about the increasing EMFs, and bad
interference with computers and TVs has been reported --- see for
example, the item in PC Magazine, visible at
http://www.pcmag.com/article2/0,4149,1382851,00.asp ,
especially the second and third paragraphs.

Yes, you have to make sure electronic equipment is well shielded,
nowadays. (And maybe our brains will have to be shielded in the
future!) Some devices have to be "guarded" in addition to being
"shielded," and an explanation of the difference is in the electronics
textbook that I wrote, which includes many other simplified
experiments. You can find (very complimentary!) descriptions of this
easy-to-read book on amazon.com by searching my name (Shanefield) and
then clicking on the blue "Customer Reviews" line.