How Does a Light Bulb Work?

Video Transcript

"Hi, I'm Steve Jones, and I am going to tell you how a light bulb works. Well, first of all we have to see the construction of the light bulb. In fact, the working part is what we call a filament which is a thin piece of metal, and this gets white hot. It glows very, very hot, and of course, if it was in the air it would actually burn away. So, we enclose this in a bulb of glass which is sealed with a screw thread on here to attach it to the place it's being put, and we have two legs here on which we hang the filament. These are usually tungsten. The electricity comes in at one connection here at the bottom in the middle, and it goes up through here through the wire, and then down and comes out through the screw thread at the side, or sometimes we've got what's called a bayonet connection. It depends on which country you're in. Either a screw thread or a bayonet. A bayonet is just flat. You push it in, and turn it, and it jams. So, the glass bulb is evacuated; that is, there is no air in here. If there were air in here this, as soon as it got hot, would burn away. You don't want that. What you do is you put in a gas which won't allow burning. You remove the oxygen in here, and you put in argon gas, so this contains argon and won't burn so this can become white-hot and it will produce mainly light. Well, not mainly light, actually, about ten percent is light. Most of it is heat, and this glass bulb will get very hot. Normally, these bulbs have a power of around sixty watts, so the sixty watts is a an average. They, in fact, go from something like twenty five watts up to two hundred and fifty watts. A two hundred and fifty watts lamp will actually use a current of one ampere. A twenty five watt, of course, will produce, will use a tenth of an amp. So, there we have an electric light bulb and how it works."