Home
Back
Resistance Formula:
| From: | To: |
The resistance formula in terms of conductivity calculates the electrical resistance of a material based on its physical dimensions and conductivity properties. It provides a fundamental relationship between material properties and electrical behavior.
The calculator uses the resistance formula:
Where:
Explanation: The formula shows that resistance is directly proportional to length and inversely proportional to both conductivity and cross-sectional area.
Details: Accurate resistance calculation is crucial for electrical circuit design, material selection, power transmission systems, and electronic device development.
Tips: Enter length in meters, conductivity in Siemens per meter (S/m), and cross-sectional area in square meters. All values must be positive and non-zero.
Q1: What is the difference between conductivity and resistivity?
A: Conductivity (σ) is the reciprocal of resistivity (ρ). Conductivity measures how well a material conducts electricity, while resistivity measures how strongly it resists electrical current.
Q2: How does temperature affect resistance?
A: For most conductors, resistance increases with temperature due to increased atomic vibrations that impede electron flow. The relationship is described by the temperature coefficient of resistance.
Q3: What are typical conductivity values for common materials?
A: Silver: ~6.3×10⁷ S/m, Copper: ~5.96×10⁷ S/m, Aluminum: ~3.5×10⁷ S/m, Iron: ~1.0×10⁷ S/m, Sea water: ~5 S/m, Glass: ~10⁻¹² S/m.
Q4: When is this formula most applicable?
A: This formula works best for uniform materials with constant cross-section at constant temperature. It assumes homogeneous material properties throughout the conductor.
Q5: How does cross-sectional shape affect resistance?
A: The formula uses cross-sectional area regardless of shape, but current distribution may vary with shape. For high-frequency applications, skin effect becomes important.