Plasma Ball

Edited by David Kang
Plasma Balls are novelty items that can be use to demonstrate scientific concepts. 
Those Plasma Balls are really fascinating. There is a high voltage source 
attached to the inner ball that causes a current to flow to the nearest point 
with a lower voltage. The ball is filled with a gas that glows when it has 
electricity flowing through it. When nothing is touching the ball, the current 
just flows anywhere onto the ball. When you touch the ball, some of the current 
can flow through the glass and into you. Because your body is providing a place 
for the current to flow, the electricity keeps flowing and the lines of current 
can stay connected to the point on the ball that you are touching.
Wikipedia article
Another site that explains plasma balls
A boatload of questions answered about plasma balls





Plasma Ball Experiments
Needed: Plasma Ball
        Fluorescent light bulb
Warnings: The plasma ball is usually harmless, but I would still recommend 
warning those with any type of heart condition.

What to do: Place your hand on different spots of the sphere. It will collect 
more "sparks" than the rest of the sphere. Also, place the fluorescent bulb next 
to the sphere. It should light up. By holding the bulb in different places, you 
can show that the electricity is actually moving from the sphere to you. If you 
hold the bulb in the middle, only half of it will light. On the other hand, if 
you hold the bulb at one end, the entire bulb should light up.

What to say: The plasma ball is the same concept as the Van de Graaff generator. 
Instead of discharging from a large sphere to a smaller one, the plasma ball 
discharges electricity from a small center ball to a larger surrounding sphere. 
The sphere is filled with a gas that emits light of different colors as 
electricity is passed through it.

The Physics: The plasma ball uses fluorescence to produce the different colors 
of light. Fluorescence occurs as electrons pass through and collide with the 
atoms of the gas inside of the sphere. As a result of the collisions, some of 
the atoms get raised to a higher energy level. Very quickly, usually about 10^-8 
seconds, the excited atoms will return to their normal energy states. 
This process involves the emission of a photon. Since the energy levels of a 
particular substance are very quantified, the photon emitted will have a 
particular energy. This particular energy produces light of a specific 
wavelength and thus a specific color. Einstein showed that photons of energy E 
will have a frequency, f, equal to E/h, where h is Planck's constant (6.63 x 10^
-34). The wavelength of the light can be found by wavelength = speed of light/ 
frequency. (from MadSci.org)
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What you need:
•    Plasma Ball (available at toy stores and online)
•    Fluorescent Light Tube
•    Wooden chair or stool to stand on (or anything not metal)
•    Pennies

Try This:
1.    Turn off the lights so that you can see the plasma ball glowing.
2.    Put your hand on the plasma ball. What happens?
3.    Now bring the fluorescent light tube close to the plasma ball. What happens?
4.    This step requires a friend, so have one close by and ready to help. Stand on the chair or stool and put your hand on the ball. Now have your friend hand you the light tube. Do you see it light up? What happens if your friend lets go? Be careful to not touch the ends of the light tube – it gets hot!
5.    Put a penny on the top of the plasma ball. Carefully touch the penny with another penny. Don’t use your finger – you’ll get a shock!


What’s going on?
The plasma ball is a miniature Tesla coil. Inside the ball is a coil of wires that have electrons going through them oscillating at a very high frequency. This shakes the atoms around the wires so hard that their electrons start to fall off! Inside the glass globe is a partial vacuum. This just means that some of the air has been sucked out. Because there is not as much air in there, it is easier to make electric sparks that can be seen.

The electrons then travel out into the air from the glass ball. We know this because the plasma ball lights up the light bulb. If you touch the plasma ball, all of the electrons will go through you to the ground. You see only one big spark inside the ball where you put your hand. If you stand on a stool, you are insulated from the ground and get filled with electrons. This means you can light up a fluorescent light bulb! (from University of Wisconsin)



Large plasma ball in action from the Ontario Science Center


What happens when you put a fluorescent light bulb next to a plasma ball? 

Cool trick, but I wouldn't try this right underneath a smoke alarm





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