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# Calculate Resistivity

Simple calculator for the resistivity (line resistance) and the line conductance of a cable. To calculate the resistivity and line conductance, you need the length and cross-section (or diameter in the case of a round cross-section) of the conductor and the specific conductance or specific resistance of the material. Please enter one value each for three of these four value categories to calculate the fourth value.

The formulas are :
R = ρ * l / A
A = π * d² / 4
σ = 1 / ρ
G = 1 / R

Units: Ω = ohm, S = siemens

 Length l: mmcmdmmkminftydmi Diameter d: mmcmdmminft Cross-section A: mm²cm²dm²m²sq insq ft Material: aluminiumirongoldcoppersilver Specific conductance σ: m / ( Ω * mm² ) = m * S / mm² Specific resistance ρ: Ω * mm² / m Line conductance G: μSmSSkSMS Resistivity R: μΩmΩΩkΩMΩ

Example: a 5 kilometer long copper cable with a diameter of one centimeter has a line resistance of approximately 1.08 ohms.

The resistance results from three factors: the length, the cross-sectional area and the material. The longer the cable, the higher the resistance. The cross-section is assumed to be the same along the entire length or at least that the average cross-section is known. Usually the cross-sectional area is a circle. The conductance always refers to a specific material that the conductor is made of throughout. This conductance only applies to a specific temperature or temperature range, with the specified values ​​being around 20 to 25 degrees Celsius. For other temperatures, you have to look in the relevant tables. Superconductors are of course not taken into account here, because their resistance is zero and their conductivity is infinite and infinite is hard to calculate with.

Copper is usually used as a material for conductors. This has a very good conductance. Silver and graphene would be even better, but these are also considerably more expensive. The previously mentioned superconductors without electrical resistance generally only work at very low temperatures, which rules them out for larger applications such as power grids and household applications. Even high-temperature superconductors require temperatures well below -100 degrees Celsius or extreme pressure, which is not any easier to handle.

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