How It Works: Why Resistance Increases with Temperature (Metals)

⚙️ How It Works: Why Resistance Increases with Temperature (Metals)

At higher temperatures, the metal ions in the wire vibrate more vigorously. This increases the chance that a free electron will collide with an ion as it moves through the wire.

Each collision slows the electron down, transferring some of its kinetic energy to the ion as thermal energy (heat). More collisions = more opposition to flow = higher resistance.

This is why a filament lamp has a non-linear V-I graph: as more current flows, the filament heats up, its resistance increases, which limits further current increases. The graph curves upward (V increases faster than I).

For a thermistor, the opposite happens: it's made of semiconductor material where higher temperature frees more charge carriers, so resistance decreases as temperature rises. This makes thermistors useful as temperature sensors in thermostats and fire alarms.