Tag Archives: Thomas Alva Edison

How Do I See the End of 2013?

It is with some degree of sadness that I mark the passing of the incandescent light bulb.

Actually it is for one reason in particular – you could understand, and therefore teach others how a light bulb work. If you run electricity through a high resistance wire, the electric energy becomes heat and light.

You could tell your kids how Thomas Alva Edison knew he needed the resistance, and a vacuum would keep the filament from burning out immediately. How, as he tried different materials for the filament, he said, “I have not failed. I’ve just found 10,000 ways that won’t work.” How Edison then went on to invent many things – how to record sound, motion pictures, medical fluoroscopy and how these inventions spawned whole industries.

How it was this date in 1879 when Edison first demonstrated the light bulb to the public and that one of those basic light bulbs has been glowing almost continuously for 112 years.

How when you add a second electrode to an incandescent light bulb and you have a diode rectifier; add a third, making a triode that can amplify an electric signal – an important step leading to the proliferation of radio and eventually television.

What a great teaching tool!


Can you clearly explain how an energy efficient compact fluorescent bulb works? How about an LEDs (light emitting diode)?

Didn’t think so – me either.

The Advance of Technology



1963: “Teacher, how does a light bulb work?”

What an excellent topic for Science class today. Several inventors had built light bulbs, but they didn’t last very long. Thomas Alva Edison figured out how to make the first practical light bulb after years of research. He was a prolific inventor with over 1,000 patents including how to record sound and motion pictures.

For the light bulb he figured out that he’d need a filament – that is something that glows – and it needed to be in a vacuum so it wouldn’t just burn up. A glass bulb would maintain a vacuum and let the light shine through, but the filament was a problem. He tried all types of exotic metals, including silver, gold and platinum, but eventually settles on carbon. One story is that he carbonized a piece of cotton thread for the filament.

Today we use tungsten for the filament, but the rest of the design hasn’t changed much. They’re reliable – in fact there are several bulbs that were installed at the beginning of the twentieth century that are still burning today.

2003: “Teacher, how does a one of those curly light bulbs work?”

Well, let’s Google that. Hmmm, it was invented back in 1976 by George Hammer who worked for GE , but they didn’t want to spend the money to manufacture them. Eventually, the Chinese started making them.

They use less electricity than incandescent bulbs but the light is kind of funny colored. They’re supposed to last for five years, but around my house they seem to last about half as long as the old style light bulbs they replace.

They’ve got mercury in them, which is a hazardous material. The expression “As mad as a hatter” referred to the fact that hat makers used mercury and as they absorbed it through their skin, they exhibited erratic behavior, so if you break one, you have a problem.

There’s a phosphor inside that glows. That’s about the best I can do to explain it.

2013: “Teacher, how do light emitting diode – LED light bulbs work?”

Ooops, we’re out of time for science. Put your science books away and get out your social studies books so we can learn all about how Congress gets things done.