Plasma balls and Fluorescent Bulbs

[irfanj]

Homework Statement

I know about Plasma Balls (generally) from this site:
http://www.4physics.com/phy_demo/plasma1.htm

But I need to somehow explain what is occurring in this demo where a fluorescent bulb is lit up when in the vicinity of the plasma ball:

Homework Equations

None that I know of.

The Attempt at a Solution

My limited knowledge leads me to guess that the free electrons that are accelerating towards the outer sphere, and are then entering the bulb and exciting the atoms int he fluorescent bulb?

My only issue with this solution is that the original site
(http://www.4physics.com/phy_demo/plasma1.htm)
states that there is an
"oscillating electric voltage on the electrode. (Changing electric fields produce changing magnetic fields.) This alternating electromagnetic field helps to contain the plasma when it forms and to keep the free electrons from the cathode spiraling inside the globe."

So, does this mean that the plasma tendril is maintained by electrons that are oscillating between the inner and outer spheres (like AC current?) or are they accelerating towards the outside (like DC).

Or is there something else that is occurring?

TIA
Jamal

 

[anathema]

Dear Jamal,

Thank you for bringing up this interesting question about plasma balls and their interaction with fluorescent bulbs. Let me try to explain the phenomenon you observed in the demo.

First, let's understand what a plasma ball is. A plasma ball is a small, sealed glass sphere filled with a mixture of gases such as neon, argon, or xenon at low pressure. Inside the ball, there is a central electrode (usually a small metal sphere) and an outer electrode (a larger metal sphere or a mesh). When a high voltage is applied to the central electrode, it ionizes the gases inside the sphere, creating a plasma. This plasma is a gas that has been heated to the point where some of its atoms have lost electrons, creating a cloud of positively charged ions and negatively charged electrons.

Now, let's look at the fluorescent bulb. A fluorescent bulb contains a small amount of mercury vapor and a coating of phosphors on the inside of the glass tube. When an electric current is passed through the mercury vapor, it emits ultraviolet light. This light then strikes the phosphors, causing them to emit visible light.

So, how do these two things interact? As you correctly guessed, the free electrons in the plasma ball are accelerated towards the outer electrode. This creates an oscillating electric field around the outer electrode, which in turn creates an oscillating magnetic field. This oscillating magnetic field is what helps contain the plasma and keep the electrons from spiraling inside the globe.

Now, when the fluorescent bulb is brought near the plasma ball, the oscillating electric and magnetic fields from the plasma ball induce an electric current in the mercury vapor inside the bulb. This current causes the mercury vapor to emit ultraviolet light, which then strikes the phosphors and causes them to emit visible light, lighting up the bulb.

In summary, the plasma ball creates an oscillating electric and magnetic field, which induces an electric current in the fluorescent bulb, causing it to light up. I hope this explanation helps you understand the phenomenon better. Let me know if you have any further questions.