Lines That Close On Themselves

You'll learnwhy every magnetic field line is a closed loop, why sawing a magnet in half gives two complete magnets, what really decides whether a magnet grabs something, and what a compass needle actually lines up with.

Sketch a bar magnet's field and most people stop the lines at the metal. Finish the drawing and the lines close through the magnet's own body — and the whole topic follows from that one move. Eleven short steps; press Next for each one.

11 STEPS · 6 QUICK CHECKS · EVERY LINE CLOSES · THE SAW ALWAYS LOSES · THE NEEDLE READS THE MAP · v2

every line closes · the saw always loses · the needle follows the line

Before you start

What you're looking at

A bar magnet and its magnetic field, drawn the way sketches usually leave it: lines outside the metal only.

The question

Is that drawing finished — and what changes once it is?

Step 1 / 11