Earth Science · Earth's Magnetic Field
Earth's Magnetic Field: Why Does a Compass Point North?
Explore why a compass needle turns north, how Earth's magnetic field guides navigation, and why nearby metal can mislead it. Includes an interactive route challenge, a hands-on test, printable worksheet, answer key, and teacher slides for Grade 4.
Read the science notes ↓
A quick look inside this lesson
What happens in class?
Question to start with
What stays nearly the same as the case turns?
What students actually do
Notice the needle's direction and write a prediction.
Evidence of learning
Distinguish field direction from map north.
One question from the printable worksheet
A needle turns when a metal lunchbox is placed next to it. Write ONE fair test to check whether the lunchbox is affecting it.
Lesson plan
Earth's Magnetic Field: Why Does a Compass Point North?
A step-by-step guide to help you teach this lesson.
Extra context for teachers
Science notes: Earth's Magnetic Field: Why Does a Compass Point North?
A short concept refresher and teaching perspective. The full procedure, printable materials, and student tasks are available in the lesson resources above.
Science in context
How does a compass know which way to turn?
Imagine a small bar magnet mounted on a smooth pivot inside a compass. Its two ends respond to the surrounding magnetic field. Earth's field can turn the needle without touching it. The painted north-seeking end is the end we usually use for directions.
Magnetic north is close to, but not exactly, true north
Geographic north is defined by Earth's rotation axis. A compass follows the local field, so its reading may be a few degrees east or west of true north, depending on where and when you are. On a real hike, navigators use a current map and local declination information for precise bearings.
What makes the idea observable?
A compass rests on a level table. Turn its case slowly. The colored needle end tries to return to nearly the same direction. What invisible interaction could cause that?
Predict first. A compass is a tiny magnet that can rotate, not an arrow programmed to point up on a map.
A misconception worth addressing
- A compass needle follows the local magnetic field, not necessarily the geographic pole.
- A wooden stick is a comparison object, not proof that all nonmetal objects cannot affect fields.
Teacher tip
- Provide a large directional floor mat and move a marker.
- Allow a tactile or enlarged compass rose.
Verified curriculum references
Plan with confidence
Lesson overview
What students will learn
- Use a compass model to explain how a magnetized needle aligns with the direction of Earth's local magnetic field.
- Follow cardinal directions to map a short route and distinguish magnetic north from true north.
Key science ideas
- Moving electrically conducting liquid deep inside Earth helps create its magnetic field; Earth behaves approximately like a large magnet, but the field is more complicated than a simple bar magnet.
- A compass needle is magnetized. When it can turn freely, it settles along the horizontal direction of the magnetic field near it.
- The north-seeking end generally points toward magnetic north, which is not always the same as geographic, or true, north.
Lesson at a glance
- Grade 4
- 50 min
- ~12 min prep
- 7 materials
What’s included
- Lesson Plan
- Investigation
- Teacher Slides
- Printable Worksheet
- Teacher Answer Key
- Interactive Activity
- Vocabulary