I'm sure that everyone has been wondering about that age-old question. What is the resistivity of iron? Well, I am about to make it so you can rest easy and answer that question for you. Electrical resistivity is a property of any object or substance to resist or oppose the flow of an electrical current. According to Ohm's law, the quantity of resistance in an electric resistance determines the amount of current flowing in the circuit for any given voltage applied to the circuit. The unit of resistance is the Ohm. The standard abbreviation for electric resistance is R and the symbol for ohms in electric circuits is the Greek letter omega, Ω. The resistivity of a material is usually represented by the lower-case Greek letter rho (ρ) and is derived from the formula RA/l, where R is the resistance of a uniform specimen of the material, having a length l and a cross-sectional area A. The units of p are ohm-meters. The reciprocal quantity is the electrical conductivity of the material. In most cases, as the temperature of a metal is reduced, the resistance usually reduces until it reaches a constant value. This value is known as the residual resistivity. The value depends on specific characteristics, such as the type of metal, its purity and thermal history. In some cases, some materials lose all electrical resistivity at sufficiently low temperatures. This occurrence is known as superconductivity. Resistivity is most commonly tested at a temperature of 20 °C. At this temperature, the resistivity of iron is approximately 100 nΩ·m. I am glad that I was able to answer that age-old question and I hope that you can now rest easy and use my data for good and not evil.

Jonathan Ruditser -- 2004

Editor's Note: The vertical axis on this graph should read "Resistivity (Ohm meters)".