Resistance and resistivity — common mistakes

Always remember the condition for Ohm's Law: constant temperature. If temperature changes, resistance might change, and the component is likely non-ohmic. Pay close attention to this detail in exam questions!

Resistance ($R$) is a property of a specific component, depending on its material, length, and cross-sectional area. Resistivity ($\rho$) is an intrinsic property of the material itself, independent of the component's dimensions, defining its inherent ability to resist current flow.

In metals, higher temperatures increase atomic vibrations, leading to more collisions with charge carriers and thus higher resistance. In NTC thermistors (common type), higher temperatures provide enough energy to release more free charge carriers, thereby decreasing resistance and increasing conductivity.

Despite requiring very low temperatures, superconductors are crucial for applications needing powerful, stable magnetic fields without energy loss. Examples include MRI scanners for medical imaging, maglev (magnetic levitation) trains, and potentially for highly efficient power transmission grids in the future.