- From the I/V graph, the ratio V/I increases as current increases. Resistance of the filament lamp increase with temperature.
Reason: As the potential difference across a filament lamp increases, the current increases and the energy dissipated, as heat, increases, resulting in a higher temperature. As the temperature increases, resistance of the filament increases. The collision between the free electrons and the lattice ions increases due to more rigorous vibration of the lattice ions.