Back to knowledge base
Basic Theory

Resistance Concept and Calculation

Resistance Concept and Calculation Definition of Resistance Resistance is a measure of a conductor's opposition to current flow. Resistance Law - R: Resistance…

About 5 min read beginner
ResistanceResistivityCalculationBasics

Resistance Concept and Calculation

Definition of Resistance

Resistance is a measure of a conductor's opposition to current flow.

Resistance Law

R = ρ × L / S
  • R: Resistance (Ω)
  • ρ: Resistivity (Ω·m)
  • L: Length (m)
  • S: Cross-sectional area (m²)
  • Influencing Factors

  • Material: Different materials have different resistivity
  • Length: Longer conductors have higher resistance
  • Cross-sectional area: Thicker conductors have lower resistance
  • Temperature: Metal resistance increases with temperature
  • Common Material Resistivity

    MaterialResistivity (Ω·m, 20°C)
    Silver1.65×10⁻⁸
    Copper1.75×10⁻⁸
    Aluminum2.83×10⁻⁸
    Iron9.78×10⁻⁸

    Resistance Calculation Example

    Example: Calculate the resistance of a copper wire with length 100m and cross-sectional area 2.5mm².

    R = ρ × L / S
    R = 1.75×10⁻⁸ × 100 / (2.5×10⁻⁶)
    R = 0.7Ω