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.
