## Monday, May 23, 2011

### More Plasma Fun

We had so much fun playing with our plasma ball, we decided to try making some plasma of our own! According to YouTube, this is easy to do if you have (a) a microwave and (b) a grape. This experiment was about the most exciting thing we have ever tried in our kitchen. Here's how to do it:

Materials
• large juicy grape
• knife
• microwave-safe plate
• microwave-safe tall heavy glass, preferably tapered (like a beer or coke glass)
1. Cut a grape in half across the middle. Take one half and cut the long way, leaving a bit of skin to hold the halves together.
2. Open up the halves and place grape on a small plate. Remove the rotating turntable in the microwave. Place the plate in the microwave.
3. Turn off the lights. Set the microwave for 5 seconds (but stand by to hit "Stop" when needed). You should see sparks and a puff of “flame.” That is the plasma.

Here's something even cooler: To make a kind of Jacob's Ladder, cover the grape with the glass. Make sure the glass is sturdy, or it may break! Set the microwave for 5 seconds (but stand by to hit "Stop" when needed). You should see blobs of plasma rising in the glass over and over.

Here's an explanation of how a microwave creates plasma from Naked Scientists:
A microwave oven heats up food using microwaves - these are electomagnetic waves that cause electric current to move back and forth between the two halves of the grape. This current is concentrated in the piece of skin between the two, which will heat up and dry out. The current then has to move through the air, creating a spark.

The spark is created when the electric field rips electrons off atoms. These can then move freely and carry electric current. A gas with free electrons and positive ions is also known as a plasma. This plasma conducts electricity and can absorb microwaves. Sometimes the plasma gets big enough to absorb enough microwaves to keep growing.

And from Physics Forums:
There's two clean grape surfaces that are separated by a fraction of a millimeter near the corner of an air wedge. The electric field between the grape portions at the tip of the wedge is large enough to cause breakdown in the air gap, making a plasma ball there.