Electric Resistivity Converter
Convert electrical resistivity units — Ω·m, Ω·cm, μΩ·in, and more. Accurate online resistivity converter for material science, semiconductor design, and conductor selection.
Understanding Electric Resistivity
Electric resistivity measures how strongly a material opposes electric current flow. You express resistivity in ohm-meters (Ω·m). This intrinsic property depends on material composition and temperature.
Resistivity differs from resistance. Resistance describes a specific object. Resistivity describes the material itself, independent of shape or size.
Resistivity Formulas
ρ = R × A / L
Definition: Resistivity equals resistance times cross-sectional area divided by length.
R = ρ × L / A
Resistance calculation: Resistance equals resistivity times length divided by area.
ρ(T) = ρ₀ × [1 + α × (T - T₀)]
Temperature dependence: Resistivity at temperature T equals reference resistivity times temperature coefficient factor.
Example: Copper wire 100 m long with 1 mm² area has R = 1.68 × 10⁻⁸ Ω·m × 100 m / 1 × 10⁻⁶ m² = 1.68 ohms.
Common Resistivity Conversions
| Ω·m | Ω·cm | μΩ·cm |
|---|---|---|
| 1 × 10⁻⁸ | 1 × 10⁻⁶ | 1 |
| 1 × 10⁻⁶ | 0.0001 | 100 |
| 1 × 10⁻⁴ | 0.01 | 10,000 |
| 0.01 | 1 | 1,000,000 |
| 1 | 100 | 100,000,000 |
Material Resistivity Reference
| Material | Resistivity (Ω·m) | Temp Coefficient (1/°C) |
|---|---|---|
| Silver | 1.59 × 10⁻⁸ | 0.0038 |
| Copper | 1.68 × 10⁻⁸ | 0.0039 |
| Gold | 2.44 × 10⁻⁸ | 0.0034 |
| Aluminum | 2.82 × 10⁻⁸ | 0.0043 |
| Iron | 1.0 × 10⁻⁷ | 0.0050 |
| Silicon | 6.4 × 10² | -0.075 |
| Glass | 1 × 10¹⁰ | - |
| Rubber | 1 × 10¹³ | - |
Practical Applications
Conductor Selection
Copper offers lowest cost per conductivity for wiring. Aluminum provides lighter weight for overhead lines. Gold plating prevents corrosion on connectors.
Semiconductor Manufacturing
Doping controls silicon resistivity from 0.001 to 100 Ω·cm. Four-point probe measurements verify wafer resistivity. Resistivity mapping ensures uniform device performance.
Heating Element Design
Nichrome alloy provides 1.1 × 10⁻⁶ Ω·m resistivity. High resistivity and temperature stability suit it for heating applications. Resistance wire length determines heater power.
Grounding Systems
Soil resistivity affects grounding electrode design. Values range from 10 Ω·m for wet clay to 10,000 Ω·m for dry rock. Soil treatment reduces resistivity for better grounding.
Frequently Asked Questions
How does temperature affect resistivity?
Metals increase resistivity with temperature. Semiconductors decrease resistivity with temperature. The temperature coefficient quantifies this change per degree Celsius.
What is the difference between resistivity and resistance?
Resistivity describes material properties in ohm-meters. Resistance describes specific objects in ohms. Resistance depends on resistivity plus dimensions.
Why is copper used for electrical wiring?
Copper offers excellent conductivity, good mechanical properties, and reasonable cost. Only silver conducts better but costs far more. Aluminum provides lighter weight for overhead applications.
How do you measure resistivity?
Use a four-point probe for semiconductors. Measure resistance of a known geometry sample for bulk materials. Soil resistivity meters use spaced electrodes for ground testing.
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