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.
'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.
