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Easy demo of powerful EMFs around us

D

Dan Shanefield

Jan 1, 1970
0
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.
 
B

Bob Masta

Jan 1, 1970
0
On 3 Feb 2004 09:25:22 -0800, [email protected] (Dan Shanefield)
wrote:

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.

I suspect much of this was simple transformer action, with
the house wiring as the primary and the "antenna" as the
secondary. (At least for the 60-120 Hz stuff.)

Another eye-opening thing you can do is to use a small
telephone pickup coil and monitor amp/speaker, like
those sold by Radio Shack. Bring the pickup near
various water pipes and you'll find all sorts of interesting
"ground" currents, due to household loads and/or
transformer coupling.




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
J

John Larkin

Jan 1, 1970
0
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.


Since the wire was insulated ("an extension cord") there was no DC
path for the diode return current. So how can it charge the cap?

John
 
R

Roy McCammon

Jan 1, 1970
0
Dan said:
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."

That nice warm sunlight is a powerful em field.

Heck, we are mostly an em field.
 
D

Dan Shanefield

Jan 1, 1970
0
John Larkin said:
Since the wire was insulated ("an extension cord") there was no DC
path for the diode return current. So how can it charge the cap?

John

The insulated antenna (just an extension cord) went to one terminal of
an ac voltmeter, and the other terminal went to the ground (a rod
poked into the earth, outside). There was up to 3 volts ac, and with
a diode in series, a capac. was charged up. Then the capac. had as
much as 5 V of dc.
Dan
 
D

Dan Shanefield

Jan 1, 1970
0
Roy McCammon said:
That nice warm sunlight is a powerful em field.

Heck, we are mostly an em field.

I certainly had nothing to do with the fact that "EMF" is written to
mean "RF e'mag. fields" these days. (Pretty dumb acronym, especially
since it used to mean electromotive force in the older physics
textbooks.) But that's the way it appears in IEEE and other
literature, lately, ignoring lightwaves and other such fields (even
ignoring static fields). Anyhow, it's RF.
Dan Shanefield
 
D

Dan Shanefield

Jan 1, 1970
0
On 3 Feb 2004 09:25:22 -0800, [email protected] (Dan Shanefield)
wrote:



I suspect much of this was simple transformer action, with
the house wiring as the primary and the "antenna" as the
secondary. (At least for the 60-120 Hz stuff.)

Another eye-opening thing you can do is to use a small
telephone pickup coil and monitor amp/speaker, like
those sold by Radio Shack. Bring the pickup near
various water pipes and you'll find all sorts of interesting
"ground" currents, due to household loads and/or
transformer coupling.




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

My biggest surprise was with a straight wire (extension cord) out in
the backyard, far from the house and from telephone poles. Another
surprise was measuring 20 volts of as, between the outside ground rod
(poked into the earth) and the green safety ground wire in my house,
even with no big appliances running. (It wouldn't have surprised me
if there had been a clothes drier going, but there wasn't --- at least
not in my house.)
Dan Shanefield
 
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