Resistance in the Real World

Every material resists current, but the range is staggering. Copper resists so little that a kilometer of wire barely slows electrons down. Glass resists so much that it stops them entirely.

Temperature changes everything. Heat a wire and its resistance increases, because the atoms vibrate more and get in the way of electrons. This is why incandescent bulbs are most fragile at turn-on: a cold filament has low resistance, so a surge of current rushes through.