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Q & A: steel shielding a magnet

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Most recent answer: 09/07/2012
Q:
In a science experiment,when steel is placed between a magnet and a paper clip, the paper clip dropped almost immediately. Why? Thanks, "A Mom who can't believe that she likes science"
- Maggie (age 48)
raleigh, nc, usa
A:
Nice question. The steel you found is evidently somewhat magnetic, like most steel except for some stainless. That doesn't mean that its magnetic domains stay lined up like in a permanent magnet, but it does mean it has lots of little domains. The field from your permanent magnet partly lines up the domains in the steel, so that it becomes magnetic too. The field from the steel largely cancels the field from the permanent magnet out on the paper clip side, so the paper clip falls. One way you can picture this is to think of magnetic field lines from your permanent magnet. The magnetizable steel sort of sucks up those lines into itself, leaving fewer out near the paper clip.

We could go farther into explaining that if you'd like to ask a follow-up.

Mike W.

(published on 05/16/2013)

Follow-Up #1: re-routing magnetic field lines

Q:
Isn't it true that magnetic shielding materials (ie iron, etc) just "reroute" magnetic flux lines or fields through them making them unavailable, for the most part, to produce the field in the space they would have occupied?
- steve (age 57)
chicago
A:
Yes, that's another way to express the same idea.

Mike W.

(published on 09/07/2012)

Follow-up on this answer.