Grades K–2 · Machines
How can a compass needle keep pointing the same way?
A compass can turn in someone’s hand while its needle keeps pointing the same way. The needle is a small magnet. It rests on a support that lets it turn freely.
In the diagramThe case turns around an aligned needleCase turned a quarter-turn clockwiseNESWMarked endNeedleLocal magneticdirectionThe marked end follows the local magnetic direction
Earth has magnetism around it, called its magnetic field. That field turns the needle until it lines up. The marked north end then points along the local magnetic direction.
This direction is often near north on a map, but not exactly the same. The case can turn around the needle. Nearby magnets can change the direction that the needle follows.
About this explanation
Starting knowledge: Recognize a magnet and distinguish a moving pointer from its surrounding case.
Sources
- NOAA National Centers for Environmental Information — Geomagnetism Frequently Asked Questions: Compass