1. What is Electrical Resistivity?

Electrical resistivity (ρ) is a fundamental property of materials that quantifies how strongly they oppose the flow of electric current. For copper wire, it's typically about 1.68×10⁻⁸ Ω·m at 20°C.

2. How Does the Calculator Work?

The calculator uses the resistivity equation:

Where:

• \( \rho \) — Resistivity (Ω·m)
• \( R \) — Electrical resistance (ohms)
• \( d \) — Wire diameter (meters)
• \( L \) — Wire length (meters)

Explanation: The equation relates the resistance of a uniform wire to its physical dimensions and the intrinsic resistivity of the material.

3. Importance of Resistivity Calculation

Details: Calculating resistivity helps in material characterization, quality control of wires, and designing electrical systems with proper conductor sizing.

4. Using the Calculator

Tips: Enter resistance in ohms, diameter in meters, and length in meters. All values must be positive numbers. For best accuracy, measure diameter precisely.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical resistivity of copper?
A: Pure copper at 20°C has ρ ≈ 1.68×10⁻⁸ Ω·m. This may vary slightly with purity and temperature.

Q2: How does temperature affect resistivity?
A: Resistivity increases with temperature. For copper, it increases by about 0.0039 per °C above 20°C.

Q3: Why use diameter instead of area in the formula?
A: Wire diameter is often easier to measure directly. The area is calculated as πd²/4 within the formula.

Q4: What units should I use for accurate results?
A: Use meters for length and diameter to get resistivity in standard Ω·m units.

Q5: How does this differ for other materials?
A: The same formula applies, but each material has its own characteristic resistivity value.