Why Iron Remembers: teacher key

Magnets, grade 9 edition, written for 9th grade. Inside a magnet, in a wire and in Earth's core, and why Earth's poles can swap.

Read the book. Print this page for the key.

Questions and answers

What happens to the domains in a permanent magnet?
- They line up in the same direction (answer)
- They melt
- They stop moving
About how big are domains in ferromagnetic material?
- Between 0.1 mm and a few mm (answer)
- About a mile
- Smaller than an atom
What did a compass needle do near a current-carrying wire?
- It melted
- It aligned perpendicular to the wire (answer)
- It pointed away
What happens to Earth's magnetic field during a pole reversal?
- It disappears completely
- It doubles
- It weakens but does not completely disappear (answer)
What happens to a permanent magnet if it is heated enough?
- It loses its magnetism (answer)
- It grows stronger
- It turns into iron filings