# Trying to apply electric current to plasmas in motion.

1. Feb 2, 2012

### dougettinger

How do you represent a certain mass of plasma (ions and free electrons) traveling inside a containment from point A to point B as "I", electrical current?

Trying to make a connection, Doug Ettinger

2. Feb 6, 2012

### dougettinger

I seem to be drawing a blank. Perhaps someone knows about flourescent lighting. Electric potential between the ends of a flourescent light causes the gas inside to be ionized. Are there any laws for describing what happens ?

Ionizingly, Doug Ettinger

3. Feb 6, 2012

### Drakkith

Staff Emeritus
The current flowing throught he plasma is equal to the current flowing through the rest of the power supply circuit in a florescent light. However I don't know the equations for determining this in a confined plasma in a different situation.

4. Feb 7, 2012

### dougettinger

How does a flourescent light work? Does the heat from the current ionize a certain gas that is enclosed inside the lamp? Why does flourescent lighting require ballast devices?

Learning more about plasma, Doug Ettinger

5. Jun 5, 2012

### EulersFormula

A flourescent light works because as the cathode is heated, it thermionically emits electrons which undergo collisions with vaporized Mercury atoms. As the Mercury atoms de-excite, they release a UV photon. This photon then interacts with the phosphor on the wall of the chamber causing it to emit visible light.

They require a ballast because they have negative differential resistance. This means that as more current is applied to the fluorescent tube, the resistivity actually decreases. This is dangerous because there is no limit to the amount of current running through the tube.

A ballast is connected in parallel with the fluorescent tube to limit the current running through it. There are many kinds, but the simplest is an inductor placed in series with the fluorescent lamp and the starter.

The starter is a device that provides a voltage spike to the tube to initiate the discharge.