Light bulbs.

[magicbeatle]

How can you tell the difference between an Incandescent Light Bulb, and a Fluorescent Light Bulb. Do they look different?

[Catso]

They don't necessarily look much different now, there are some very normal looking fluorescent bulbs.

Put the bulb in a dimmer circuit. A fluorescent won't dim properly.

[heathfield]

Normally the incandescent bulb will simply have a metal end-cap on the glass bulb. The flourescent bulb will have a plastic housing attached to the glass bulb, containing the necessary electronic circuitry.

[Space]

fluorescent light bulbs are bigger, colder, and more energy efficient.