Electrical conductivity describes a material’s ability to permit the flow of electric charge. Iron, like all metals, is a conductor of electricity. Its ability to conduct is a direct result of its atomic structure, which features electrons that are not tightly bound to individual atoms. Its performance is significantly lower than some other common metals. The practical use of iron in electrical applications often depends on a balance of its moderate conductivity with its other material properties, such as strength and cost.
The Science of Metallic Conduction
The ability of iron and other metals to conduct electricity stems from a unique atomic arrangement known as metallic bonding. In this structure, the outer-shell, or valence, electrons of the metal atoms are not fixed in place. Instead, they are delocalized, forming a mobile “sea of electrons” that surrounds a lattice of positively charged metal ions. This model explains the high conductivity of metals because these electrons are free to move throughout the entire material.
When a voltage is applied across a piece of iron, an electric field directs the motion of these delocalized electrons. The electrons drift collectively toward the positive terminal, creating an electric current. As they move, the electrons collide with the stationary positive iron ions in the crystal lattice. These collisions impede the flow of charge, which is the source of the material’s electrical resistance.
If the electrons encounter fewer obstacles, the material’s resistance is lower, and its conductivity is higher. Factors like temperature increase the vibration of the lattice ions, which increases the frequency of electron collisions, thereby raising the electrical resistance of the iron. Impurities or defects in the metal’s structure also act as scattering centers for the electrons, further reducing conductivity.
How Iron Ranks Among Conductors
Iron’s standing among metallic conductors is best understood by comparing its performance to industry standards, specifically silver and copper. Pure iron has a relatively high electrical resistivity. At room temperature, the resistivity of pure iron is approximately 9.70 x 10^-8 ohm-meters. This value is roughly six times higher than the resistivity of copper, which is about 1.68 x 10^-8 ohm-meters.
This difference places iron far down the list of the most conductive metals, ranking below silver, copper, gold, and aluminum. The conductivity of pure iron is only about 17% of copper’s conductivity. This lower efficiency is rooted in the complex electronic band structure of iron, which limits the mobility of its valence electrons compared to copper. Furthermore, the iron used in commercial applications is often an alloy like steel, which contains impurities such as carbon that greatly increase resistivity and reduce overall conductivity.
Real-World Uses of Iron’s Conductivity
Despite its lower conductivity compared to copper, iron and its alloys, particularly steel, are widely used in applications where a balance of electrical, mechanical, and economic properties is desired. Its high tensile strength and low cost make it suitable for structural components that also need to be electrically grounded. For instance, the steel frame or chassis of a vehicle is often used as the ground plane for the entire electrical system, creating a vast, inexpensive conductor for the return path of current.
Iron is commonly employed in grounding rods and earth electrodes, where its moderate conductivity is sufficient for safely dissipating fault currents into the ground. These applications prioritize the metal’s corrosion resistance and mechanical rigidity over peak electrical efficiency. The metal’s distinct magnetic properties are also intrinsically linked to its electrical use, making it indispensable for the magnetic cores of transformers, motors, and inductors.
However, iron is almost never used for high-efficiency power transmission lines or internal wiring where minimizing energy loss is paramount. The high resistance of iron would lead to substantial energy loss as heat. For these purposes, copper remains the preferred material due to its superior conductivity, while aluminum is often chosen for overhead lines because its lower density compensates for its lower conductivity.