A 40W bulb is switched on. It burns out brighter when it was switched on than a short time later.What account for this change in brightness
resistance least when cool, current higher then, Power = i V . That is why those incandescent bulbs often burned out instantly when the switch was turned on.
The change in brightness of a 40W bulb after it is switched on can be explained by understanding how incandescent light bulbs work.
When an incandescent bulb is switched on, an electric current passes through a filament made of tungsten, which has a high melting point. The filament heats up rapidly and begins to emit light due to a process called incandescence. As the filament gets hotter, it emits more light, resulting in a brighter glow.
However, over time, the filament begins to deteriorate due to the intense heat. This can cause the filament to thin out or develop weak spots, which can lead to a decrease in brightness. In other words, as the filament wears out, it produces less light, resulting in a dimmer glow compared to when it was first switched on.
The decrease in brightness typically occurs gradually over time. So, when you notice the bulb burning out brighter when it is switched on and then becoming dimmer after a short time, it is likely due to the filament's gradual wear and tear. This decrease in brightness is a natural characteristic of incandescent bulbs and signifies that the lifespan of the bulb is coming to an end.