[WEB4LIB:14741] Re: Magnets Near PCs

[Bob Rasmussen]

On Thu, 6 Aug 1998, Jim Richards wrote:

> Corrrect me if I'm wrong, but don't the laws of magnetism say that 
> eventually the shield around the unit will become magnetised?  I 
> beleive that is why you should shield your computer, not the 
> deactivator unit.

Well my physics degree is a ways past its half-life :-) but I think:

1. If the magnet in question is just a static physical magnet, that will not
magnetize anything nearby; it takes a changing magnetic field to do that.
Otherwise EVERYTHING would be magnetized from the earth's magnetic field.

2. A static magnet CAN, however, deflect the picture on the front of a
monitor, but it has to be very close to do so.

3. Even if a shield were magnetized, it would put out a static magnetic field.

4. A shield would likely be made of aluminum, which doesn't magnetize.

5. Almost anything electrical, from a toaster to a computer, (unless it's very
constant direct current, like a flashlight) emits electromagnetic radiation
(EMR). The higher the current flow, and the higher the frequency, the stronger
the field. That's why PC makers have had to focus more on EMR as PCs have
boosted their clock speeds.

6. Either solid metal or a wire cage (Faraday cage) surrounding an object,
connected electrically to ground, will "ground out" most of the EMR.

I hope this helps. If people are having problems, particularly in an
educational setting, it'd make a good lab experiment for Physics 101. 

Regards,
....Bob Rasmussen,   President,   Rasmussen Software, Inc.

personal e-mail: ras at anzio.com
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