a student says that he has made a magnetic field with some iron fillings. what would you say to him
Answers
Answer:
Iron filings are long and thin - the same general shape as a bar magnet. When placed within a magnetic field, each filing temporarily becomes a small magnet through the process of magnetic induction. A bar magnet is a magnetic dipole - with a N and S pole, and temporarily-magnetized iron filings act a small magnetic dipoles.
When shaken onto a sheet of thick paper over a small magnet, each filing tends to realign itself along magnetic field lines. Any misaligned filing feels a rotational force (a torque) that tends to rotate the filing until it become aligned with the magnetic field lines. The N ends of individual filings are also attracted to the S poles of neighboring filings, forming long chains of oriented filings that are aligned with the ambient magnetic field lines.
There are also some interesting, and more complex, reasons why groups of filings clump together and form gaps between clumps of filings.