Electric Resistivity
How to Convert Ohm-meter to Ohm-centimeter
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.
A Material's True Resistance: Understanding Electrical Resistivity
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).
Relevant Formulas in Science and Mathematics
- Definition of Resistivity (Physics): Resistivity (ρ) is defined by the formula
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. - Relationship to Conductivity (Physics): Resistivity (ρ) is the reciprocal of conductivity (σ):
ρ = 1 / σ. - Microscopic View (Physics): At a microscopic level, resistivity is related to the number of charge carriers per unit volume (n), the fundamental charge (e), and the mean free time between collisions (τ) by the formula
ρ = m / (n * e² * τ), where 'm' is the mass of the charge carrier.
A Deep Dive into Common Electric Resistivity Units
- Ohm-meter (Ω·m): This is the standard SI unit for electrical resistivity. It represents the resistance of a 1-meter cube of the material when measured between opposite faces. It is the universal standard for all scientific and engineering work.
- Ohm-centimeter (Ω·cm): A smaller, non-SI unit that is often used in some contexts, particularly in the semiconductor industry and in American publications. To convert from Ω·cm to Ω·m, you divide by 100.