The Dynamo Under Our Feet: teacher key

Magnets, grade 11 edition, written for 11th grade. How a self-sustaining engine of iron in Earth's core makes the field that guides every compass.

Read the book. Print this page for the key.

Questions and answers

What keeps the core's field-making process going?
- Waves from the sea
- An energy source that maintains convection (answer)
- The Moon's pull
How far below the surface does Earth's core lie?
- About 2900 km (answer)
- About 29 km
- About 290,000 km
When was Earth's magnetic north pole first precisely located?
- In 1831 (answer)
- In 1086
- In 1936
How are excursions different from reversals?
- They are generally regional, not global (answer)
- They are much slower
- They happen in space
What do superconducting materials do as they transition?
- Expel magnetic fields (answer)
- Melt
- Turn into iron