Apart from making a buzzing sound and turning the screen blurry for a second 
Degaussing (from Gauss, a unit of magnetic flux density) a monitor (or a TV, for that matter) demagnetizes the metal screen which separates the red, yellow and green electron beams. Residual magnetism on this screen causes color distortion, which shows up as discolored patches in the image.
Q.E.D., What do you think of this?
monitors …are manufactured specifically for … hemisphere
Perhaps the screen discolouration is clockwise in the southern hemisphere.
Whoever wrote that should be slapped upside the head. The Earth’s magnetic field averages about a half a Gauss, which is roughly 100 times weaker than your typical refrigerator magnet. Secondly, and perhaps most importantly, how an external magnetic field affects a given monitor depends on its orientation with respect to said field. In other words, simply rotating the monitor 180[sup]o[/sup] exactly reverses the effect, thus negating any putative design factors purportedly included to account for the Earth’s magnetic field. Where do people come up with bullshit like this?
Incidentally, I emailed that website about the article in question. I’ll post here if I hear back from them.
For some reason I read the threasd title as “What does degaussing my mother do?”
I had this image of a confused woman in her 50s being attacked by her children wielding electromagnetic instruments.
An upate: It appears as though the Webopedia folks have removed that article. The Straight Dope fights ignorance and wins yet again.
<nitpick>
Psst, Q.E.D. - isn’t that supposed to be “red, blue, and green”?
</nitpick>
:smack: Red, blue and green. Right!
Indeed, red, blue and green beams/phosphors you mean.
So much unnecessary violence. Leave the slapping to Master Cecil, okay? And there should be a rule of one cite per expletive.
The effect of magnets on a CRT can give the wrong idea about field strengths. A magnet’s field rapidly falls off with distance, while the Earth’s field can be assumed constant over the whole length of the tube. You can’t really compare them.
Furthermore your typical fridge magnet is designed to make a magnetic short-circuit with the fridge door. Some have several adjacent alternating poles that cancel each other out at long range. Anybody with a cheap monitor on a swivel arm can tell you that the Earth’s field can be strong enough to affect the picture.
Secondly, and perhaps most importantly, most people are quite attached to the concept of “up”, not just because of that gravity thing. While there won’t be a preferred orientation of a CRT in the horizontal plane, the Earth’s magnetic field also has a vertical component which depends on the latitude.
Take the two extremes for example, the geomagnetic north and south poles, where the field lines are inclined perpendicular to the ground. It’s like having a weak but huge magnet under your a…feet, south side up if you’re at one place, north side up at the other. That’s already double the peak-peak difference, by the way, and you can’t turn away from it.
The vertical field strength is known for the general area where the tube is sold to, so it makes sense to roughly pre-compensate for it at the factory, to give it a wider range of conditions under which it will work properly.
The sci.electronics.repair FAQ, CRT sections 4.14-17 confirms this: http://www.repairfaq.org/REPAIR/F_crtfaq.html#CRTFAQ_020
In Google’s cached version of the Webopedia page I don’t read anything that deserves your anger. What has bitten you?
The Navy occasionally degausses entire ships to minimize their magnetic signature. It sure was interesting to see the effect that this had on all of the TV sets onboard whenever we were degaussed. Took awhile for the funky colors to return to normal.
This is basically my point right here. First of all, I never said that the Earth’s magnetic field wasn’t strong enough to have some effect. My implication was supposed to be that any effect it did have was basically negligible in comparison to much stronger local magnetic fields, like 'fridge magnets and poorly-designed speakers. I suppose I could have been clearer on this point.
Secondly, there seems to be precious little information about this on the web, other than the now-defunct Webopedia article and the FAQ you quoted from. What little I did find consisted of a parts listing for some sort of computer system, specifying different part numbers for N. Hemisphere and S. Hemisphere CRT monitors. And eve there, my gut feeling is that this amounts to little more than marketing adspeak. The problem I have with this (and the FAQ even acknowledges this issue), is that correcting for a relatively small vertical component of the Earth’s field is pointless, given the much stronger horisontal component. Unless you live at or near the poles, I fail to see how such correction is useful or even necessary.
If you think that was anger, you haven’t seen me on a bad day. No, this was merely annoyance, my friend.
Well, I misread the post as 'What does DEGASSING my monitor do". Put them together, and all in all, I prefer your mental image to mine.
Hold on… why would one want to do this? In other words, what is the utility of degaussing one’s monitor?
(bolding added)
It removes the funny colors from your monitor.
Touch a small magnet to the screen and you’ll see pretty colors.
LCD monitors are exempt from this discussion.
In a physics lab at the University of Michgan, we conducted an experiment regarding magnetism and one of our tasks was to measure both the strength and the angle of the earth’s magnetic field. The interesting point was that due to the path the magnetic field lines take in order to go to the earth’s magnetic south (geographic north pole more or less), the magnetic field was oriented at more or less like a forward slash ’ / ’ compared to the horizontal. Looking at the triangle the field makes with the horizontal and vertical (like ’ /| ') turned out to be close to 21 degrees. It would seem that with such an orientation, the effects from the vertical component would be far greater than the effects from the horizontal component. My university resides in Ann Arbor, MI, which is admittedly in the northern part of the country, a lot of cities are north enough to recieve as much or close to as much from the vertical component as we experience here.
:smack: I swear I read that other post like five times… I guess I was befuddled by all the big words.
Thanks for pointing out, uh, the obvious.
Against this I hold experimental evidence that I can wave a big bar magnet around my monitor at one foot distance without much effect, while turning the monitor around creates noticeable discolorations until it’s degaussed. These strong local fields are just that - local, and fall off with the inverse cube of distance.
As it ceases to be true somewhere north of Morocco and Mexico that the horizontal component is greater than the vertical, I have to ask for your definiton of “living near the poles”. Cite: magnetic inclination world chart (at http://www.ngdc.noaa.gov/seg/potfld/faqgeom.shtml)
This does neither prove nor disprove the existance of specifically compensated CRTs, but I think it takes a little more than one’s gut feeling before one can dismiss something as bullshit and declare oneself a winner.
Another little point in favor of the assertion is that the vertical component seems important enough that good compasses have to be made with differently balanced needles for specific latitude zones to compensate for the up/down deflection.
The first quote shares this part with the repair FAQ, but it has the advantage that it explicitly says where the author comes from!
Smile when you say that. I almost took it literally, considering that I had to have my TV repaired twice because of what must have been a design flaw. Yes, back in Ye Olden Tymes you didn’t just throw them away.
Let me add two things. The average user doesn’t have to worry about degaussing, because the monitor should do it automatically each time it is powered on. But it doesn’t hurt either to do it occasionally, and it is fun to watch.
And to nitpick myself, I used “geomagnetic” in the sense of “as belonging to the Earth”. The term “geomagnetic pole” has a special meaning which is different from what I meant.