Magnet & Compass: Magnetic Field Lines
Drag a bar magnet and a compass to see the magnetic field direction, strength and field lines.
Drag the bar magnet and the compass around. The compass needle always points along the magnetic field lines.
About the Magnet & Compass: Magnetic Field Lines
Free magnet & compass: magnetic field lines. Drag a bar magnet and a compass to see the magnetic field direction, strength and field lines. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the magnet & compass: magnetic field lines runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drag a bar magnet and a compass to see the magnetic field direction, strength and field lines. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Magnet & Compass: Magnetic Field Lines
- Use the controls to change Magnet strength, Field lines. The simulation reacts instantly.
- Pick an option such as Show, Hide to switch modes or load an example.
- Press "Flip the magnet", "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Drag the compass all the way around the magnet.
- Flip the magnet and watch the needle turn.
- Reduce the strength.
Key ideas you can learn
- Field lines leave the north pole and enter the south pole.
- A compass needle lines up with the field.
- The field is strongest close to the poles.
- Flipping the magnet reverses the field.
Where this is used in the real world
Navigation, MRI scanners, electric motors and hard drives all depend on magnetic fields.
Who is this simulation for?
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What do magnetic field lines show?
The direction a compass points and, by how close together they are, how strong the field is.
Why does a compass point north?
The Earth acts like a giant magnet, and the compass needle lines up with its field.
Is the Magnet & Compass: Magnetic Field Lines free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Magnet & Compass: Magnetic Field Lines work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.