Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I was on my workshop lab today and had to file (rub on metal surface with rough surface to smooth-en it) an iron bar. It made iron dust fall of the surface. To mark some points on the bar I then had to hammer a pointed another Iron bar over the former. What I noticed is that the iron dust that had previously fallen off were clinging on the top circumference of the pointed bar.

I have two probable explanations for this

  1. The iron dust being small acted as magnets as there are fewer magnetic domains and they essentially align on single direction so that the dust were attracted.
  2. Hitting the top of bar somehow could have magnetized the bar so that the dust were attracted

Am I correct with one or both of these explanations?

share|cite|improve this question

The impact of the hammer with the iron nail causes the magnetic domains within the nail to break loose from their current orientation. The Earth's magnetic field will then reposition the domains into a new orientation parallel with the Earth's magnetic field.

share|cite|improve this answer
If you have a magnet to begin with, hitting it with a hammer can demagnetize it. – mmesser314 May 15 '15 at 13:39
@Luftwaffe I doubt that the magnetic field of the earth would be enough to create the effect described in the OP. – gonenc May 15 '15 at 13:47
@gonenc, irrespective of Your doubts, smaller ships (esp. mine sweepers) were rotated 180 ° north-south on the wharfs at around half of the work. – Georg May 15 '15 at 15:35

Luftwaffe is probably right, but also possibly the filings or the bar were already very slightly magnetized. In that case the hammer impact on the table shakes the filings around, removing the friction that keeps them from moving toward the iron bar.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.