|
04/27/2005
Surges in Water and Elsewhere
I started this column in a wave mode. That Norwegian cruise
ship’s encounter with a 70-foot wave brought to mind my own
experience on a cruise ship in 35-foot waves off the coast of
Alaska. Those 35-footers certainly caught our attention and I can
imagine how scary a 70-foot sea must be. But, compared to the
devastation wrought by the waves of the tsunami in the Indian
Ocean, the plight of that cruise ship pales into insignificance.
As I mulled over other waves, I got a phone call from Dan, a
very good friend and loyal fan of StocksandNews. Dan lives in
Honolulu and there’s trouble in paradise. I feel it could be a
public service to inform you of the trouble. Most of us have a
“surge protector” between an electrical outlet and our computer
and other associated equipment. The surge protector protects our
computers from surges in voltage on the power line. Or does it?
Recently, the room that houses Dan’s computer suddenly filled
with acrid black smoke. The surge protector had caught fire and
the plastic casing had melted! Fortunately, it was afternoon; the
fire was spotted immediately and all is well. All, that is, except
for Dan’s computer, which is no longer functions and Dan can’t
access StocksandNews. What caused the fire? There was no
storm and no lightning to cause a power surge. Dan suspects that
the power company had some kind of problem.
At the same time, isn’t a surge protector supposed to handle a
power surge? Could the incident have anything to do with the
fact that Dan is of the school that keeps the computer turned on,
even when not in use? I’m of the school that turns the computer
off when not in use. However, except during a thunderstorm or
when I’m away on vacation, my surge protector is on all the
time. After Dan’s experience, I’m considering pulling the plug
on the protector when I turn off the computer.
How does a surge protector work? I hadn’t the foggiest idea so I
posed that question on my search engine and was led to a Web
site appropriately named howstuffworks.com. It was most
helpful and had an extensive multi-page section describing the
workings of a surge protector along with helpful tips on choosing
a surge protector for your computer. One popular design of
surge protector involves a component known as a metal oxide
“varistor”.
My dictionary defines a varistor as a semiconductor device
whose resistance varies with the voltage applied. I’m not an
electrical engineer but will give you my interpretation of the role
of the varistor in the surge protector. In the surge protector you
have several of these MOVs connected in some way to ground.
In normal operation, when the voltage at your outlet is its normal
110 or so volts, the varistor resistance is high and virtually all the
current goes to your computer. In a voltage surge, the high
voltage lowers the varistor resistance drastically; any damaging
excess current is carried away from your computer to ground.
Don’t buy inexpensive surge protectors. The really cheap ones
may not have any surge protection at all, but function merely like
extension cords to increase the number of outlets for plugging in
your computer equipment. There are also surge protectors that
employ cheaper metal oxide varistors. I found the alarming
statement that these cheaper varistors may overheat and fires are
not uncommon! At the very least, it is recommended that you be
sure that your surge protector has the Underwriter Laboratory
(UL) seal of approval, although that does not guarantee total
safety. Wouldn’t you know? I’ve just looked at one of our two
surge protectors (we have two computers) and there’s nothing at
all about its electrical characteristics, let alone a seal of approval!
Oh well, back to waves. Tsunamis have received a lot of press
the past few months but I found that the April issue of National
Geographic sums up the past, present and future of these waves
quite succinctly. The issue contains two articles, “Tsunamis –
Where next?” by Tom O’Neill and “My Seven. Waves to
Remember” by Tim Appenzeller. What causes tsunamis?
We’ve seen what a very strong earthquake under the sea can do –
millions of people uprooted and hundreds of thousands dead or
missing. The typical underwater quake occurs along a fault
where an ocean plate dives under a continental plate. The fault
between the plates gets locked in place until it finally snaps.
Over 700 miles of fault snapped last December, generating a
monumental quake measuring 9.0 on the Richter scale.
The quake lifted up the seabed on the continental plate some 16
feet, giving rise to the tsunami. The wave was only a couple feet
high as it sped along at 500 mph in the ocean but the volume of
water was huge and as it slowed down near shore wave heights
rose as high as 50 to 80 feet. Major landslides and rock falls also
trigger tsunamis. I was blown away by the reported size of the
wave that a quake-induced rock fall spawned in Lituya Bay in
Alaska in 1958. This 1,720-foot wave, much higher than the
Empire State Building, was the highest in recorded history. I
would hate to be on a cruise ship and see that wave coming!
Enough about big waves; let’s talk about smaller ones. My
friend Tom has again called my attention to an article in the New
York Times that merits attention. The article, by Matthew Wald
in the April 14 Times, is titled “Using Advanced Physics to Find
Concealed Weapons”. It deals with the use of “millimeter wave”
technology to improve security in this terrorist age.
The use of night vision binoculars or other devices in, for
example, fighting the war in Iraq, is based on the fact that we and
other objects radiate heat. This heat is in the form of infrared
radiation that is detected by sensors in the optical devices. This
infrared radiation is at wavelengths significantly less than a
millimeter. I hadn’t realized that we humans also emit radiation
at longer wavelengths, in the millimeter range up to a couple of
centimeters. When I looked up the electromagnetic spectrum in
my International Encyclopedia of Science and Technology, I
found that this millimeter wave radiation lies in the microwave
region of the spectrum, just beyond the infrared region.
Obviously, we don’t emit enough microwave radiation to cook a
TV dinner. However, it does pass through clothing and, if you
have a sensor that can detect millimeter waves you can, in effect,
see through clothing. You may remember a fuss some time ago
about an instrument being installed in some airports that not only
revealed concealed weapons but also showed rather clearly one’s
more private physical attributes. These “active” millimeter wave
machines are more like radar, beaming radiation at the subject
and looking at the reflected radiation.
The “passive” devices we’re discussing don’t beam anything at
you but just pick up what you emit. This more diffuse radiation
apparently doesn’t reveal the intimate details of your person, but
guns or other weapons emit different levels of millimeter wave
radiation and show up on a scanner. I found on its Web site that
the Royal Military College of Canada is also interested in these
passive millimeter wave devices to spot humans inside buildings,
an obvious plus for troops fighting in urban settings.
OK, I’m finished and, after posting this column, I’ll pull the plug
and try to squirm under my desk to check out my other surge
protector. Will it also be just a fancy extension cord? Stay
tuned.
Allen F. Bortrum
|
