Labs / Physics
Magnetic Field Lines
Pick a source, then drag it around and slide the little compass through the field lines — the needle always snaps to the local field direction. The lines and iron filings are computed live from the magnetic dipole and Ampere's-law formulas, and the readout shows the field at the compass.
|B| 0 µTdir 0°
What to try
- Park the compass in one spot, then flip the polarity. Which way does the needle jump, and why?
- Switch from the bar magnet to the straight wire. Why do the field lines turn into closed circles instead of arcs from N to S?
- Move the compass twice as far from the wire. Does the field strength halve, or fall off faster than that?
- Compare the current loop with the bar magnet up close. Do they look like the same kind of field from far away?
- Crank the current or strength to maximum. What changes about the field lines — their shape, or just the reading on the compass?