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To convert from Ohm-meters (Ω·m) to Ohm-centimeters (Ω·cm), you multiply by 100, since there are 100 centimeters in a meter.
Example:
Convert a resistivity of 1.68 × 10⁻⁸ Ω·m (the resistivity of copper) to Ω·cm.
(1.68 × 10⁻⁸ Ω·m) * 100 = 1.68 × 10⁻⁶ Ω·cm
Answer: The resistivity of copper is 1.68 × 10⁻⁶ Ω·cm.
Electrical resistivity (often represented by the Greek letter ρ, rho) is a fundamental, intrinsic property of a material that quantifies how strongly it resists the flow of electric current. It is a measure of a material's inherent ability to oppose electrical flow, regardless of its size or shape. A material with low resistivity is a good conductor, allowing charge to move easily, while a material with high resistivity is a poor conductor (an insulator). This property is the direct reciprocal of electrical conductivity.
Resistivity is what allows us to compare the conducting abilities of different materials on a level playing field. For example, we know that copper is a better conductor than steel, and resistivity provides the specific numerical value for that comparison. The resistance of an actual object, like a piece of wire, depends not only on the material's resistivity but also on its length and cross-sectional area. A long, thin wire will have a higher resistance than a short, thick wire made of the same material. Resistivity, however, is a constant for the material itself. This concept is crucial for engineers and material scientists when selecting materials for any electrical application, from designing efficient power transmission lines (requiring low resistivity) to creating heating elements for a toaster (requiring high resistivity).
ρ = R * (A / L), where 'R' is the resistance of a uniform specimen of the material, 'A' is its cross-sectional area, and 'L' is its length.ρ = 1 / σ.ρ = m / (n * e² * τ), where 'm' is the mass of the charge carrier.Resistivity is an *intrinsic* property of a material itself (e.g., the resistivity of pure copper). Resistance is an *extrinsic* property of a specific object (like a wire) that depends on both the material's resistivity and its physical shape (length and thickness). A long, thin copper wire has a higher resistance than a short, thick copper wire, but the resistivity of the copper is the same in both.
Silver has the lowest electrical resistivity of any metal, making it the best electrical conductor. However, copper is used much more widely for wires because its resistivity is only slightly higher, and it is far less expensive.
Insulators have very high resistivity. Materials like quartz, glass, and PTFE (Teflon) have extremely high resistivity values, which is why they are used to prevent the flow of electricity.
For most metallic conductors, resistivity increases as temperature increases. The increased thermal vibration of the atoms in the metal lattice disrupt the flow of electrons, making collisions more frequent. For semiconductors, resistivity generally decreases with temperature.
A toaster works by passing current through a heating element. This element must be made of a material with high resistivity (like a nickel-chromium alloy). According to the power formula P = I²R, this high resistance causes the wire to dissipate a large amount of electrical energy as heat, making it glow red hot and toast the bread.
A material with zero electrical resistivity is called a superconductor. It can conduct electricity with no energy loss. This property only occurs in certain materials when they are cooled below a very low 'critical temperature'.