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 tension force as the divergence of the Maxwell tensor: which gives the electromagnetic force density in terms of Maxwell stress tensor, formula_24, and the Poynting vector, formula_25. Now, the magnetic tension is implicitly included inside formula_24. The implication of the above relation is the conservation of momentum. Here, formula_27 is the momentum flux density and plays a role similar to formula_28 in Poynting's theorem. Magnetic tension force The magnetic tension force is a restoring force (SI unit: Pa·m) that acts to straighten bent magnetic field lines. It equals: It is analogous to rubber bands and their restoring force. The force is directed