Incandescent bulb for 220V vs 110V and difference of their resistance?
The different resistances of those incandescent bulbs are made with different length and different diameters of tungsten wires. A very long and thin wire is wound to a filament, sometimes even a double filament. But the values calculated from power and voltage are the resistances in hot condition. The resistance at cold condition is much lower. I have here a bulb with 120 W at 230 V and a resistance at room temperature of 29 Ohm. The resistance in hot condition at 2950 K is 440 Ohm. If we assume a diameter of 0.1 mm for that tungsten filament wire, we can calculate a length of 4.3 m for a resistance of 29 Ohm. I used the specific resistance of tungsten 0.0528  Ω ⋅ mm²/m for that calculation.