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Low temp physics. (Fridge magnets).

Soapy Sam

Penultimate Amazing
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Oct 23, 2002
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I have a mystery.
On Wednesday morning, I took a bottle of milk from the fridge.It was frozen. Odd. On investigation, the compressor seemed to be running constantly. The temperature control knob had no effect. I assumed the thermostat had failed.
Now, this machine is 20 years old and has served its time. It has internal cracks and blotches- It's done. I need a new one. I switched it off to defrost, then decided to restart it, with the door held just ajar by a cloth-that way it won't freeze everything and when the compressor gives up the ghost, I'll get a new one.

Today (Thursday), I found the nine fridge magnets had fallen off the door onto the floor. They will pick up paperclips, but will not support their own weight on a vertical surface. Also, the door will not stay closed- it seems the door magnets have been degaussed.

The only magnet on the fridge unaffected is one from a deceased hard drive, which seems as strong as ever. (Of course it was vastly stronger to start with, which is why I use it to hold a shopping list notepad).

Two other fridge magnets, stuck to the frame of the cooker, are just fine. And no, there is no sign that the fridge has caught fire, exploded or melted, so let's not hear about Curie Point.

The fridge is in fact still working and the compressor has started cycling on and off again as normal, as if there had never been a problem. I'm not sure when this happened, but it definitely was not the case at 18:00 yesterday.

To add to the mystery;- I do not know when this demagnetization took place, but about midnight last night, the Sony E200 17" CRT on my PC died. Picture went crazy and then dark. I checked the video card by plugging in an old 15"CRT, which worked in safe mode, but kept losing the plot when XP kicked in full speed. Too many add-on drivers, I suspect. Which is why I am now looking at a 17" Philips B4 TFT. (Nice, but I liked that Sony).

I'm completely baffled. Can anyone suggest why this would happen? Could the two events be related? (I can't think how.)
The fridge and the PC are powered by different 240V ring main circuits. They don't share a common supply until the 100A fuse on the main power into the flat. I'm assuming the monitor failure is just that and the coincidence is just coincidence, but can anyone explain the magnets?

nb. No, I don't buy fridge magnets. My mother does.

ps. I don't think it's EMP either- I suspect I would have heard the bang.
 
Guessing game at best but I'll take a shot.

They are two separate issues I believe.

The fridge control or timer are kaput ( prob the control).
The way these normally function is to measure the temp and cycle the compressor on and off depending on temperature . There is ( in most modern fridges anyway ) a defrost mechanism that cycles on and off to prevent frost build up and the door sticking closed . There is also an inherent entropic principle involved. The seal at the door is the junction where the cold of the inside air meets the outside air so the rubber gasket is very cold inside and very warm outside.

Now I'm guessing that either the door wasn't closed all the way or the timer stuck on. The colder the inside gets the greater the differential temperature is at the seal, the greater heat at the junction ( and the door )...or the timer stuck on defrost mode and heated up the door ( I vote No #1) In either case the door got hot and slightly de-maganitized the fridge stick-ons.(thier cheap magnets anyway)

The second problem is just that your monitor died . When you reboot in safe mode ( lo res ) you must change settings from the Sony to the new monitor before you allow the machine to goto regular mode.

edit to add : aw hell I did not read closely enough. You propped the door open which means that the compressor stayed on and also the timer cyclled on for the defrost circuit which heated the door. The test of the control is simple turn it all the way up and all the way down...if you hear a click, chances are that the control is ok and the timer is bad. If you want to play appliance mechanic the steps are easy enough also.
 
Till- They are , as you say, weak magnets. My point is that two of them are stuck to the frame of the cooker, one on the oven door itself. The door is frequently too hot to touch for more than a few seconds, yet the magnets are fine.

I think there has to be a magnetic explanation rather than a temperature related one. If nothing else, the margarine and frost in the fridge would have melted.

I think Agamammon may be right. It's a miracle!
 
I have no idea what happened, but I have to say that I really enjoyed the thread title!
 
Soapy Sam,

The issue IS magnetic, heat a magnet and it de-magnitizes it ! What happens is that all the iron molecules are pointing in the same direction , when you heat a magnet they randomize again.
I'm not sure what you mean by a cooker ( stove?) but the heat and its effects would be lessened by a lower temperature where the are affixed. There is also a possibility that the defrost mechanism has a coil around the door that generates a degaussing field. Submit a magnet to an alternating field and it also randomized the direction of the iron. Whereas the stove does no such thing.

You try the monitor fix?
 
Cooker, yes , electric stove. Believe me, the oven door gets a lot hotter than the fridge could without melting the dairy produce and probably the inner lining of the fridge. Even so, the oven door is nowhere near the Curie Point of the magnet or it would have fallen off years ago. (I just checked that it's not welded on by congealed gravy. Nope, I can pull it off easily.)

It's a puzzler. I've often defrosted the fridge without this happening. The door magnets are in the form of a plastic coated strip around the doorframe. There is no sign of scarring, burning or anything, but the door won't stay shut and the fridge magnets won't stick to anything!

It's one of those "A Quantum Black Hole Ate My Hamster" mysteries. The coincidence of the monitor dying had me wondering about voltage surges, but there's really no way. More likely is the fact that I had just downloaded about 20MB of M$ patches, including one for Invidia graphics cards! (Am I paranoid, or what?)
The Sony CRT shows no sign of life. The video card is fine. The new 17" TFT is just lovely- and the bedroom door shuts now! (The old CRT got in the way). I will try the CRT on the PC at my mother's house tomorrow. (My emergency data backup), but I'm not sanguine about its chances.
 
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