Why does the resistance of a metal depend on its temperature?

• A. The hotter the metal, the greater the vibration of the ions
• B. The colder the metal, the more electrons are emitted
• C. Temperature changes electron charge
• D. Temperature changes material color

Answer: (A)

In metals, electrical resistance comes from electrons moving through a lattice of positively charged ions. As temperature increases, the ions vibrate more strongly. These bigger vibrations cause electrons to scatter more often as they travel, shortening their average distance between collisions. With more frequent scattering, the electrons’ drift under an applied voltage slows down, so the resistance increases. The other ideas don’t explain resistance in metals: simply having a hotter temperature doesn’t cause more electrons to be emitted in bulk conduction, the electron charge is essentially constant with temperature, and a change in color isn’t what sets the resistance.