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Electric netting is renowned for being resource hungry meaning that a given net requires a certain strength energiser to be able to run it. All reputable energisers (of course ours are totally reputable) will give figures for how many nets will be run by that energiser. This is generally referring to standard 1 meter high by 50 meter long nets.
If we look at the popular Farmer N25, it will power 15000 meters of fencing but will only run 11 nets. If we multiply the nets out we will find that there is only 6050 meters of wire in the 11 nets suggested so there is a massive discrepancy between the two. If a company only quotes a length of fencing it is possible to be misled to assume that a large number of nets may be charged by a particular energiser. If no figures are quoted then it will be prudent to assume only 40% of that is available for netting.
Why does this Happen.
An electric fence relies upon the energiser sending down the wire a high voltage charge for only 1/300 of a second, once a second *, When that happens a magnetic field is created around that wire. In netting these wires are all close together so the magnetic fields around each wire interact with each other so increasing the resistance. This continually happens as the charge collapses and re-created every time a charge is sent down the line. This is highlighted by what is known as the Hall effect.
The general theory of the Hall effect and the change of resistance in a magnetic field expresses these quantities in terms of several integrals over the surface of the Fermi distribution. Measured with a constant current, resistance increases under the influence of a magnetic field, and that this increase depends on the strength of the field and its direction with reference to the current in the wire. If the current traversing the bismuth is oscillatory, the resistance has a value O outside the magnetic field, or in a field in which the lines of force are parallel to the wire which is less than R. If, however, the wire is perpendicular to the lines of force of a field greater than 6000 C.G.S. units, the resistance O is greater than R; the difference O – R increases from this point rapidly as the strength of the field increases. The difference between the resistances to an increasing and decreasing current increases with the rate of change in the strength of the current and this difference is more marked with strong currents than with weak. (Hope you understood that)
Not only is it affected by the oscillation of the electric current, the type of conductor also affects the reaction. A Copper/Zinc alloy will carry more current but be less affected by magnetic affect than those made of Stainless Steel. High diamagnetism and strong resistance go together. Stainless Steel has a higher resistance coefficient than a Copper/Zinc alloy in filaments of the same diameter.
Ambient temperature has a further effect. As the temperature increases so does the resistance in the wire increase which then has a greater effect on the magnetism resulting in a greater in-line resistance. This "greater" is actually very small in real terms (about 0.002 Ohms increase between 10 and 20 degrees C.) so is discounted.
* These figures do vary between both models and manufacturers.