An ohmic conductor has a straight-line I–V graph at constant temperature. A filament lamp’s resistance increases as its temperature rises, so its graph curves. A diode conducts readily in one direction but has a very high resistance in the reverse direction. Example: Identify a straight I–V line through the origin. It represents an ohmic conductor at constant temperature because I is proportional to V. A correct answer needs an appropriate unit as well as a numerical value. Check your reasoning.