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Magnets in Pipes!

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Cold Magnets in Pipes!

We've seen what happens when strong magnets are dropped down copper pipes, and we've seen what happens if the pipes are cooled in liquid nitrogen. So... what happens if the magnets are cooled in liquid nitrogen?

Announcer: Frostbite Theater presents... Cold Cuts! No baloney!

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: Earlier, we did an experiment where we dropped a magnet down a copper pipe that had been cooled in liquid nitrogen. A great question came up in the comments: "What happens if you cool the magnet?"

Steve: It's an interesting idea and we would try it if we had some liquid nitrogen.

Oh, wait! We have liquid nitrogen!

Joanna: Duh!

Joanna: In general, cooling a magnet makes it stronger. However, it turns out that neodymium magnets, like ours, get stronger up to a point. Cool them past that point, and they get weaker. At liquid nitrogen temperatures, neodymium magnets lose about 10% of their room temperature strength.

Steve: This is easier to see if we slow things down by using cold pipes. In the first trial, the cold magnet has just been removed from the nitrogen. It's weaker than the room temperature magnet, so it falls faster.

Joanna: 20 seconds later, we try it again. The cold magnet has warmed to the point where it's just as strong as the room temperature magnet, so both magnets fall at the same rate.

Steve: When we try again 10 seconds later, the cold magnet is stronger than the room temperature magnet, so it falls slower.

Joanna: Thanks for watching! I hope you'll join us again soon for another experiment!

Steve: So that was actually way more interesting than we had any reasonable right to expect.

Joanna: This is true.

Steve: Good question. Good job!

It was probably me who asked it.

Joanna: Yeah!

Steve: I hope somebody actually does ask the question!

Joanna: Good job, Steve!

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