What is an Incandescent Lamp?

Mary McMahon
Mary McMahon

An incandescent lamp, otherwise known as a light bulb, is a form of electric light. Incandescent bulbs are so effective that they have been widely adopted around the world for all sorts of lighting applications, from illuminating the inside of an oven to providing safety illumination for parking lots. The mechanics of the incandescent lamp are remarkably simple, and the design has not deviated very much from the earliest prototypes.

Incandescent light bulbs.
Incandescent light bulbs.

This type of electric light works by subjecting a very fine filament to an electric current. If the electric current is high enough, it will heat up the filament and excite the atoms inside, eventually causing them to give off light. The property of incandescence, in science, involves glowing in response to heat, and the incandescent bulb is probably the most famous demonstration of this property.

Standard incandescent lamps are often used to illuminate homes.
Standard incandescent lamps are often used to illuminate homes.

Humphry Davy is often given credit for first demonstrating that if a metal filament was subjected to an electrical current, it would give off light. A bit of trial and error occurred after his demonstration before the incandescent lamp was introduced. First, people had to find a metal which would make an effective filament, and then they had to address the common problem of oxidation. An exposed filament wouldn't last very long, necessitating the creation of a vacuum around the filament, which meant that someone have to develop an envelope to enclose it. A glass bulb was found to be ideal, and the incandescent lamp was born.

The modern incandescent lamp is usually filled with an inert gas, rather than operating in a vacuum. The life of a light bulb can be quite impressive, with bulbs tending to last longer when they are left continuously on, rather than being turned off and on frequently. Life of the bulb can also be influenced by the types of light fixtures it is used in, the amount of light it is intended to produce, and factors such as trauma; the filament will often break if an incandescent light is jostled while it is on, for example.

Incandescent lamps come in a wide variety of configurations. The intensity of the light can be varied by adjusting the wattage and the composition of the bulb; clear bulbs will give off bright, clear light, for example, while frosted bulbs will mute the light. Size and shape can also be varied, with some bulbs being designed to mimic candles, while others are intended to fit into unique or small spaces, so they require an unusual shape and attached socket to connect with a source of electrical current.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


I have switched from incandescent lamps to compact fluorescent lamps in every room of my house. They cost a little more than incandescent bulbs, but they save enough energy to be more than worth the price.

They also don't get as hot as the incandescent bulbs. They still generate some heat, but not enough to be comparable to the old kind.

I have noticed the difference on my electric bill since making the switch. Even though they say that CFLs can expose you to mercury if they break, I will continue to use them and just be really careful when changing the bulbs.


The lamp on my bedside table uses a miniature incandescent lamp. I only have to buy a 40 watt bulb for it, since the light doesn't need to be that bright.

I use it to read by as I'm winding down for the night. I think that the low wattage actually helps me get sleepy. It lets my brain know that it's dark outside and it's time to get some rest.

I used to read with the overhead light on, but that was much too bright. I have a 100 watt incandescent lamp in my bedroom light fixture, so I only turn that on when I'm going to be awake for at least a few more hours.


@lighth0se33 – I have heard that these Christmas lights can pose a fire hazard. With incandescent lamps, the bulbs become hot to the touch.

Also, the colored paint on the outside will start to flake off over time, especially if you hang your lights outdoors. It's no wonder you don't see a whole lot of incandescent Christmas lights anymore.

I once read that they use several hundreds more watts than LED lights. That alone should motivate people to get rid of their old lights.

My sister still uses these. I bumped into one of the bulbs last year, and I drew back my arm in pain. It was so hot!


Another incandescent lamp type can be found on some strings of Christmas lights. I remember the old school kind with the colored shells that my parents used to string across the porch during the season.

The bulbs were small when compared to regular light bulbs, but they were much bigger than the LED models of today. When people do clip art to illustrate Christmas lights, they usually draw the old incandescent bulbs, because they are so much more noticeable and nostalgic.

The only thing I didn't like about these lights was the heat they put off. It made me a bit nervous, since they were so close to the wood of the porch.

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