1. What is Electrical Resistance?

Electrical resistance is a measure of the opposition to current flow in an electrical circuit. It's measured in ohms (Ω) and depends on the material's properties and its physical dimensions.

2. Understanding the Resistance Formula

The resistance formula is:

Where:

• \( R \) — Resistance in ohms (Ω)
• \( \rho \) — Resistivity of the material (ohm-m)
• \( L \) — Length of the conductor (meters)
• \( A \) — Cross-sectional area of the conductor (m²)

Explanation: Resistance increases with length (more collisions for electrons) and decreases with cross-sectional area (more paths for electrons).

3. Factors Affecting Resistance

Details: Resistance depends on:

• Material (resistivity)
• Length of conductor
• Cross-sectional area
• Temperature (not accounted for in this simple formula)

4. Using the Calculator

Tips:

• Enter resistivity in ohm-meters (e.g., copper ≈ 1.68×10⁻⁸ Ω·m)
• Length must be in meters
• Area must be in square meters
• All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between resistance and resistivity?
A: Resistivity (ρ) is an intrinsic property of the material, while resistance (R) depends on both the material and its dimensions.

Q2: Why does resistance increase with temperature?
A: In most conductors, higher temperature increases atomic vibrations, causing more electron collisions and higher resistance.

Q3: What are typical resistivity values?
A: Silver ≈ 1.59×10⁻⁸ Ω·m, Copper ≈ 1.68×10⁻⁸ Ω·m, Aluminum ≈ 2.65×10⁻⁸ Ω·m.

Q4: How does wire gauge affect resistance?
A: Thicker wires (larger area) have lower resistance. AWG standard defines wire diameters.

Q5: What's the difference between AC and DC resistance?
A: For AC, skin effect can increase effective resistance at high frequencies, which isn't accounted for in this DC formula.