Brightness of the filament bulb depends on power. The design of the filament is such that it uses tungsten (high resistivity), coil up (to increase the length) and thin tungsten filament (small cross-sectional area). These features are to let the tungsten filament achieve a certain amount of resistance, so that when current flows through, energy is transferred electrically to the internal (thermal) store of the filament, so that it is hot and the filament glow and gives out l

Solutions: Option B As lamp X is thicker and shorter , these two factors make the resistance of X lower than Y . Recall: Length...