The effectiveness of an electric fence is directly related to the "sting" supplied by the electric charge being transmitted through a conductor (be it a tape, rope or wire). The quality of this electric "sting" is also directly dependant to the quality of the conducting material transmitting the energy from the Fence energiser to the target animal.
The electrical conductivity of a metal is a measure of how easily electrons move through that metal. Metals generally have a high electrical conductivity because of their definitive property of sharing electrons. Electrical Conductivity (also known as resistivity, specific electrical resistance, or volume resistivity) quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electrons between molecules. Of the two commonly used metal alloys in fencing, Copper has a very low resistivity (1.68×10−8) compared to Stainless Steel (6.90×10−7) - The SI unit of electrical resistivity is the ohm/metre (Ω/m) although other units like ohm/centimetre (Ω/cm) are also in use. As an example, if a 1m×1m×1m solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1Ω, then the resistivity of the material is 1Ω/m. The greater this figure reflects a greater resistance and a poorer conductivity.
The higher this Ohms per meter figure is - the less of the current that is delivered to that important sting. The lower the Ohms/metre is, the more electricity it will carry and deliver an effective sting.
For example:- An energiser capable of energising 9klm with a 0.05 Ω/m. conductor will be reduced to just 1.3klm if you use a conductor of over 10 Ω/m.
Conversely, when an energiser is used to charge 1.3 klm of fence using a good conductor will use far less energy than using a poor conductor;- your batteries will last far longer.
There is a very simply maxim regarding resistance and current flow;-
- low resistance (low Ohms/metre) = high current flow
- high resistance (High Ohms/metre) = low current flow
The better the conductivity of the conducting material in the fence (rope, tape, twine or wire), the lower the Ohmic value. Many energisers quote "miles/kilometres of wire" to indicate the capacity of that energiser. This is typically a laboratory test using the best conducting materials available under perfect conditions and normally only quote the best figure. Using a 3 Joule mains energiser different conductors may be quoted as follows;
- Less than 0,05 Ohm/m → very good conductivity, 30000 metres
- 0,05 - 0,5 Ohm/m → good conductivity, 18000 - 30000 metres
- 0,05 - 6,0 Ohm/m → average conductivity, 5000 - 18000 metres
- 6 - 15,0 Ohm/m → poor conductivity, 500 - 5000 metres
The resistance of a conductor is further affected by the temperature of the wire - as this rises so does the in-line resistance causing a further drop in effectiveness. A wire with a high Ohms/meter rating will heat up when energised by a fence energiser with a high energy output due to the resistance by the metal to transfer electrons exacerbating the problem. It is not advisable to use poor quality conductors with a high output energiser.
Caveat emptor - let the buyer beware. Generally the conductivity is reflected in the price of the product. There are plenty of un-declared products on the market and also many copycat products that look very similar to quality products - make sure you know what you are buying. Copper or Aluminium is by far the best conductor, but invariably more expensive. This may be off-set by having more steel conductors but it is important to compare conductivity (however it is delivered) to get the best return per pound spent. A tape with 6-8 conductors may not be as economical as one with 3-5. As a general rule, a product with only steel conductors is normally of a lower conductive quality, normally reflected in the lower price.
The strength of the conductive material is supplied by the plastic strands, not by the thin stainless steel or copper filaments. Fencing Rope is stronger than tape as the strands are closely wound and so combine their strength better than Horse tape. Life of the conductor is determined by two natural factors- Ultra Violet rays and wind action.
1/.Ultra Violet rays from natural sunlight reacts with and breaks down the polyplastic material. It will cause it to go brittle and change colour. This may be protected by the inclusion of stabilising compounds into the plastic. This is expensive so those sold with a warranty have a high inclusion of this compound whilst cheap products will tend to be unprotected and so not last as long. Tape has a greater surface area exposed to sunlight and is more affected by wind action. Because of these two constraints the life of tapes may be substantially shorter than rope.
2/. Wind action causes the conductors to flap and so flex the metal filaments back and forth.
This results in metal fatigue and breaking. Again the cross section of tape presents a greater target to the wind so that it will flex more than the round rope. The only advantage tape has over rope is it's visibility.
There is only one thing to be considered when looking at Electric fence tapes, rope or twine - that is the conductivity (the ability to transmit electricity) of the material. An Elephant or horse will not be fenced in by plain rope or tape but apply an electric current and ANY terrestrial animal is capable of being contained.