9702 · 9.3
Resistance and resistivity — FAQ
Frequently asked questions for 9702 Resistance and resistivity. Direct answers first, then deeper explanation — then practise with marking.
What is the key difference between resistance and resistivity?
Resistance () is a property of a specific component, depending on its material, length, and cross-sectional area. Resistivity () is an intrinsic property of the material itself, independent of the component's dimensions, defining its inherent ability to resist current flow.
Why does temperature affect the resistance of metals and thermistors differently?
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.
What are some practical applications of superconductors, even with their critical temperature challenges?
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.