Video transcription

Hi, I'm Steve Jones and I'm going to tell you how electricity lights up a bulb. Well, the bulb doesn't really light up unless there is a coating on it, it is the filament inside which lights up and the filament is made usually of something called tungsten which is a very hard material and last a long time. Eventually the tungsten will wear out, it will burn away and that's when you say the bulb goes because it bulb burns out it literally burns away. But exactly how does this work? Well, tungsten has resistance. Resistance is the ability of a material to allow or not allow electricity to run through it. If it has a high resistance, then it stops electricity running through it or when the electricity runs through it, it produces a lot of heat. So the tungsten has resistance, it gets very hot but getting hot is no good, we don't want it how, we want it so hot it starts to glow, it'll glow red hotter, yellow hotter, white. And when it's glowing white, it's producing light. In fact, of the energy going into this filament lamp, 90% is going to turn out as heat. This gets very hot. 10% turns up as light and that 10% is what lights your room. This is why the cool lamps, the type of long tubes that you get nowadays are much better because nearly 15% of them, 15% of the energy is actually produced as heat and 65%, 70% as light so they're much more efficient. So basically that is how electricity lights up a bulb.