Earth & Environment

How does a light bulb waste energy?


This is best demonstrated when you look at how old or incandescent light bulbs work. They have a thin piece of wire called a filament, that energy in the form of electricity flows through. The filament is made of molecules of tungsten, which is a solid. As a solid, the particles are closely packed but when additional energy is put into them they vibrate against each other so much more and they need to get rid of that extra energy.

We can’t make energy disappear, we have to convert it to something else. So the molecules of tungsten convert the extra energy into light and heat. Obviously, light is a useful side effect of the extra energy as that is what we use it for. However, all the energy from the electricity causing the tungsten molecules to vibrate that becomes heat, is wasted. That is, unless you are using the light bulb to heat something…