What four things affect the resistance of an electrical conductor?

• A. Material, cross-sectional area, length, and temperature.
• B. Material, temperature, and color.
• C. Diameter, length, and conductivity.
• D. Resistance, voltage, and current.

Answer: (A)

Resistance in a conductor comes from four main factors: the material it's made of, its cross-sectional area, its length, and the temperature.

Material determines resistivity, which is how strongly the material resists the flow of electrons. A metal with high resistivity impedes electrons more than one with low resistivity, so the intrinsic property of the material sets a baseline resistance for a given size.

Cross-sectional area matters because it’s the number of available paths for electrons to take. A larger area means more parallel paths for current, which lowers resistance; a smaller area squeezes those paths and raises resistance. Mathematically, resistance is inversely proportional to area.

Length affects resistance in a direct way: longer conductors force electrons to travel a longer path, which increases the chances of scattering and interaction with the lattice, so resistance grows with length.

Temperature influences resistance because materials change how easily electrons move as they heat up. For most metals, increasing temperature raises resistivity, so resistance goes up with temperature. Some materials behave differently, but the common rule for metals is that resistance increases with temperature.

Other options either omit a key factor (like cross-sectional area) or replace a fundamental factor with something unrelated to how resistance is determined, such as color or voltage/current, which are related by Ohm’s law but do not set the resistance itself.