Magnetometer Carl Friedrich Gauss, head of the Geomagnetic Observatory in Göttingen, published a paper on measurement of the Earth's magnetic field. It described a new instrument that consisted of a permanent bar magnet suspended horizontally from a gold fibre. The difference in the oscillations when the bar was magnetised and when it was demagnetised allowed Gauss to calculate an absolute value for the strength of the Earth's magnetic field. The gauss, the CGS unit of magnetic flux density was named in his honour, defined as one maxwell per square centimeter; it equals 1×10 tesla (the SI unit). Francis Ronalds and Charles
Magnetic reluctance towards regions of higher flux so it is always an attractive force (pull). The reluctance of a uniform magnetic circuit can be calculated as: or where The inverse of reluctance is called "permeance". Its SI derived unit is the henry (the same as the unit of inductance, although the two concepts are distinct). Reluctance can also be applied to: Magnetic reluctance </math>, formula_1, formula_2 Magnetic reluctance, or magnetic resistance, is a concept used in the analysis of magnetic circuits. It is defined as the ratio of magnetomotive force (mmf) to magnetic flux. It represents the opposition to magnetic flux, and