Why does the filament glow more brightly as the electric current in a lightbulb is increased?
The glow is dependent on two things: Spectral output, and intensity.
Current makes the temperature hotter, and so the spectrum is shifted from red to violet, which is more energetic. Also, more current increases the rate of light emission (intensity).
To understand why the filament glows more brightly as the electric current increases in a lightbulb, we need to consider two factors: spectral output and intensity.
When an electric current passes through the filament of a lightbulb, it generates heat. This heat causes the filament to increase in temperature, and as a result, the spectrum of light that is emitted shifts. At lower temperatures, the filament emits more red light, which has lower energy. However, as the temperature increases, the spectrum shifts towards the violet end of the spectrum, which is more energetic.
So, as the electric current in a lightbulb is increased, the filament becomes hotter, leading to a shift in the spectral output towards more energetic light, including violet light. This change in spectral output makes the bulb appear brighter because our eyes are more sensitive to light in the violet-blue region.
Additionally, increasing the electric current also increases the rate of light emission, which we refer to as the intensity of the light. Therefore, as the current is increased, more light is produced, leading to a brighter glow.
In summary, the filament in a lightbulb glows more brightly as the electric current is increased because the increased current raises the temperature of the filament, resulting in a shift towards more energetic light in the spectrum and increasing the rate of light emission.