Hi again U1 Structures group,
Below please find a small change to the story I sent yesterday, another example of a reversible magnetic
joint, and a nice example of making clever use of phase change control.. all this in my hotel room!
I have a change to make to the description of the magnetic hotel room door signs that I sent you
yesterday. It turns out that the doors are all-metal (covered in a wood-looking veneer), and that the
‘rubbery signs’ themselves are magnetic. I presume the magnetic material is the power embedded in the
plastic. I never heard of ‘magnetic powder’, but here it is!b
The signs are magnetic; the door is metal all over!
I also found another interesting reversible magnetic joint. This is the connection between a water
cooker and the electrical cable that supplies electrical power to it. In the past people have stumbled
over these sort of cables, upsetting the cooker and sometimes burning themselves seriously.
The cooker in my room is connected by a magnetic connection that breaks apart very easily, thus, by
easily being disengaged from the extension cable, it prevents the cooker from falling over! (This joint is
also used in some laptop computers to prevent the laptop being thrown to the ground when someone
stumbles over the extension cable.)
The magnet (silver) embedded in the connector and the two loose-fitting connection pins
The electrical plug with two mild steel strips acting as ‘attractors’ to the magnet in the
cooker, and two spring-loaded brass connectors that connect always firmly and easily with
the electrical pin contacts on the cooker
One more observation, since I have you attention. In the bathroom there is a wall to wall mirror.
Normally these mirrors steam up after a shower. In this bathroom there is a neat square clear mirror
surface, even though the rest of the mirror wall is all fogged up. The trick is a simple heating element in
the form of a picture square behind the mirror glass that prevents water vapour from condensing there.
A very elegant use of controlling ‘phase change’!
(What we see visibly happening on this bathroom mirror is also happening at the inside of walls during
the winter in Canada: warm moist air condenses inside the wall against cold surfaces in contact with the
exterior and condenses. This can be cumulative, and the wall can get soaked over time, leading to
serious deterioration of the wall materials (wood studs, sheeting). As in the bathroom, the best way to
prevent moisture build-up is ventilation. In the case of a bathroom, open the door. In the case of a wet
wall we provide ventilation where the condensation is likely to occur.)
Regards,
Pieter Sijpkes