Experiment: Microwave Light

Aim: To investigate the effect of Microwaves on an appliance that conducts electical energy(Light Bulb), when it is in water.

Method: Fill a microwavable bowl with water and put in a light bulb, make sure the end(the metal part) is fully suspended in water. Start the Microwave going.

Results: THE LIGHT BULB GLOWS!

Any ideas on why this works?

Originally posted by Billing
Any ideas on why this works?

I think I'll have to check it out myself.

In the mean time I found this online...

The light bulb:

We fill a drinking glass half full of water and place a light bulb in the glass, metal parts submerged in the water. When cooked for a few seconds we note that bulb lights up!

Why? Well, the electrons in the metal filament are jiggled around by the microwaves which causes it to heat up and glow. The water is only there to absorb excess microwaves, and it not totally necessary.

We have observed that the bulb can burn out after 10 seconds or more.

This demo can also be used to show what happens when a microwave oven is set to cook on low power. On 30%, the bulb lights for a short wile, and then goes off. Then on again, then off, and so on. The microwave generator is simply turned on and off to create an average power over time. The generator (magnetron) does not lower it's intensity, but pulses on and off.

Thanks to Mark Wexler. He showed me this demo back in 1992 or thereabouts.
home.earthlink.net...

Microwave ovens produce an electric field inside. This electric field must be causing current to flow in the water, which then goes into the light bulb and turns it on. The only way the bulb could be turning on is if electric current is flowing into it, so I suspect that this, or an explanation much like it, is the correct answer.

If my explanation is correct, then if you put the light bulb in the microwave without any water or anything else, it shouldn't turn on. The electric field is not strong enough in a microwave to overcome the dielectric breakdown of air. (if it was, your microwave would fill with sparks every time you turned it on) The light bulb does not have any sharp points on it that would act like an antenna, so it should not cause dielectric breakdown near the bulb.

I am curious, how bright does the bulb turn on? My guess is that it is rather dim, but visible. I would be extremely surprised if it glows very bright at all.

Yes, the light bulb is dim and it's intensity fluctuates