磁极探测器

Magnetic Pole Indentifier is a  smart tool for identifying the poles of magnets.

The blue end will point toward the North pole of magnet.

The red end will point toward the South pole of magnet.

 The indicator is free to rotate in transverse and longitudinal way.

The magnetic pole identifier is even more useful for showing the direction of magnetic field lines.

Magnetic field lines connect the North and South poles of a magnet.  If moved around near a magnet, the indicator will rotate and keep the magnet aligned with the magnetic field lines.