iStarSign inScience 8 · Unit 9: Magnetism · Cambridge Lower Secondary Science Stage 8
9.2 The Earth as a giant magnet
18 questions · e.g. Where does the Earth's magnetic field occur?
Questions
1. Which statement about the Earth's magnetic poles is true?
- They have not always been in the same positions.
- The Earth has no magnetic poles.
- They never move.
- They are exactly the same as the geographic poles.
2. Where does the Earth's magnetic field occur?
Check3. Which part of the Earth produces its magnetic field?
Check4. Which two magnetic metals make up the Earth's core?
Check5. From the equator, which way do the Earth's magnetic field lines point?
Check6. If the Earth were a bar magnet, which pole would be near geographic north?
Check7. How can a steel needle be magnetised?
- heat it in a flame
- stroke it many times in one direction with one pole of a magnet
- rub it back and forth with cloth
- hit it with a hammer
8. How can a magnetised needle show the Earth has a magnetic field?
- Paint it red.
- Float it on a cork in water; it turns to point north-south.
- Put it in a fridge.
- Leave it in the sun.
9. How can a bar magnet on a string show the Earth's field?
- Put it in water.
- Wrap it in foil.
- Tie it to a metal stand so it can't move.
- Hang it so it can turn freely; it settles pointing north-south.
10. Why should the clamp stand be wooden, not metal?
Check11. Which is stronger - the Earth's field where you live, or the field 1 cm from a bar magnet?
Check12. Is the Earth's field strength the same everywhere?
- It only exists in Europe.
- Yes, it is equal everywhere.
- No, it varies in different parts of the world.
- It is zero at the poles.
13. What is the core of the Earth like?
Check14. Why do sailors use compasses?
- to measure temperature
- to measure depth
- to find direction using the Earth's magnetic field
- to measure speed
15. Where is the Earth's magnetic north pole now?
- exactly at the geographic North Pole
- at the Equator
- in the Arctic, a few hundred kilometres from the geographic North Pole
- in Antarctica
16. Magnetic north moves about 60 km per year. Why can a compass still be used on a 12-hour journey?
- It moves faster than the journey.
- It stops moving during the day.
- Compasses ignore magnetic north.
- It moves only a tiny distance in 12 hours.
17. Do satellite navigation (satnav) systems use the Earth's magnetic field?
Check18. What causes the natural light displays in the night sky near the poles?
- particles from the Sun reaching the Earth's magnetic field
- light reflecting off the ice
- the Moon's gravity
- volcanoes under the ice