Resistance Calculator
Electrical resistance quantifies the opposition a circuit element presents to the flow of electric current. Formulated by Georg Ohm (R = V / I), resistance governs circuit design, conductor wire gauge sizing, and thermal power dissipation (P = I²R). This calculator computes load resistance alongside specific conductor wire resistance, voltage drops, and line power losses.
Electrical potential difference in Volts (V)
Current flow in Amperes (A)
Length of connecting conductor wire in metres (m)
Wire conductor cross-sectional area (e.g. 1.5 mm² ≈ AWG 16, 2.5 mm² ≈ AWG 14)
Conductor metal resistivity at 20°C
Apparent load resistance calculated from Ohm's Law (R = V / I)
How to Use This Calculator
- Enter circuit operating voltage in Volts.
- Enter the measured electric current in Amperes.
- Specify wire length, wire gauge area in mm², and conductor material.
- Inspect load resistance, circuit power dissipation, and wire voltage drop instantly.
Formula & Calculation Methodology
Ohm's Law states that electric current is directly proportional to applied voltage and inversely proportional to resistance. Conductor resistance depends upon intrinsic metal resistivity (ρ), length (L), and cross-sectional area (A).
Worked Example
12V automotive circuit drawing 5A through a 5-metre copper wire of 1.0 mm² area
Frequently Asked Questions
Why is silver a better conductor than copper, but copper is predominantly used?↓
Silver has the lowest resistivity of any metal (1.59 × 10⁻⁸ Ω·m vs copper's 1.68 × 10⁻⁸ Ω·m), but copper is vastly more abundant, less costly, and less susceptible to chemical tarnishing and galvanic corrosion.
What causes electrical wire voltage drop?↓
No physical wire (except superconductors) has zero resistance. Current flowing through the intrinsic resistance of the wire creates a parasitic voltage drop according to Ohm's Law (V_drop = I × R_wire), reducing available voltage at the load.
Does temperature change the electrical resistance of conductors?↓
Yes. In metallic conductors, increased temperature increases thermal lattice vibration, which scatters charge carriers and increases resistance according to R_T = R_0[1 + α(T - T_0)].
What limitation exists for non-ohmic electronic components?↓
Ohm's Law assumes linear ohmic materials where resistance is independent of current and voltage. Non-linear semiconductor devices (such as diodes, LEDs, and transistors) have dynamic, non-constant current-voltage curves.
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Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.