Science and WeatherTime-lapse video captures magnetic putty having ‘a snack’
In my daily rounds of the geeky and 'science-y' corners of the internet, I came upon a video posted by YouTube user Scott Lawson, that shows a block of iron-infused putty called 'Thinking Putty' grabbing up a small magnet and pulling it into its core.
Lawson describes what's going on:
The putty looks and feels like regular silly putty, but the difference lies in the fact that it has been infused with millions of micron-sized ferrous particles (most often iron oxide powder). The magnetic putty is not actually magnetic by itself, since the infused particles are made of iron powder.
The presence of the strong neodymium iron boron magnet (the silver cube in the video) magnetizes the ferromagnetic particles in the putty. When this happens, the ferrous particles align with each other and this alignment generates north and south magnetic poles, making the putty into a temporary magnet. Once magnetized, the putty will remain magnetized even after the rare-earth magnet has been removed from the putty. This effect persists for a few hours until thermal agitation shakes the particles and they lose their alignment.
According to Lawson, it took a total of about an hour and a half for the putty to pull the magnet to its core.
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As described by Bad Astronomer Phil Plait (where I first saw mention of this), the entire process is due to an imbalance in the forces. As soon as the neodymium iron boron cube magnetized the putty, the two magnets attract each other. The putty, having a more fluid form than the magnet cube, basically reaches out for the cube, and the greater force acting on one side of the cube (because there's more magnetized putty on that side) continues to pull the cube further and further into the putty until it reaches the centre of the block, where there's an equal amount of putty all around it.
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