Theory: In general, the further away from the equator one gets, the more steeply inclined the Earth's magnetic field is. A dip needle shows the inclination of the Earth's magnetic field.
Description: Use a compass to map out a horizontal north-south line. Align the dip needle with this line, and the needle will be aligned with the Earth's field. The inclination can be read from the scale. Note that the direction of the local magnetic field may be strongly affected by the presence of metal objects; be sure to check the area ahead of time for anything that might influence the magnetic field.
Setup time: 5 minutes
References: (available in the demo room)