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Krampf #462 Lighting a Bulb
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KRA-@aol.com
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May 09, 2006 10:18 PDT
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Robert Krampf's Experiment of the Week
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This Week's Experiment - #462 Spark Plugs
Greetings from North Florida. I have finished this year's shows for Florida
Power and Light, and am now neck deep in a new project to make a science
video series to help Florida students do better on Florida's high stakes Science
FCAT test. I am hoping to find sponsors for the series, so we can give it
free of charge to all the public elementary schools in Florida. If that works,
then I will move on to the other 49 states. It is an exciting project, and
so far, I am having a blast working on it.
This week's experiment came from a recent news story from South Florida.
Trying to show the strength of magnetic fields near power lines, the reporter
held a fluorescent light under the line, showing that it would light. This was
supposed to demonstrate that the magnetic field was dangerously strong.
What they were really demonstrating was the electric field, not the magnetic
field, and as we will see, it does not take that much of an electric field to
light a fluorescent bulb. To try this, you will need:
a fluorescent bulb
a television set
a dark room
First, darken the room. It does not have to be totally dark, but the darker
the room, the easier it will be to see the bulb light. Hold the fluorescent
bulb in your hand and stand in front of the television. Carefully, bring the
bulb near the TV screen and then turn on the television. As the picture
tube lights, you will see a bright flash from the fluorescent. Then turn the TV
off, and move the fluorescent bulb up and down near the screen. I was able
to get the bulb to light brightly at a distance of about a foot from the
screen. How can that be? Does that mean that it is dangerous to sit near the TV
screen?
First, you need to understand the two kinds of lights commonly used in our
homes. Incandescent bulbs use a tiny wire, called a filament to produce light.
To light them, you need a lot of electricity (amperage) but not much push
(voltage.) They produce light by converting electrical energy into heat,
which makes the filament hot enough to glow, giving you light.
With a fluorescent bulb, you need a lot of push (voltage), but very little
electricity (amperage.) That makes if very easy to light them using a high
voltage electric field. High voltage?!?! Wait a minute. Isn't high voltage
dangerous?
Well, we do see a lot of signs that say "Danger! High Voltage", and those
signs are warning of a danger. Voltage tells us how hard the electricity is
being pushed. If it is pushed hard enough, it can jump through the air as a
spark. That is the danger of high voltage, but it is only dangerous if the
spark that jumps to you has enough electricity (amperage) to hurt you. With s
tatic electricity, you are exposed to high voltages all the time, but the
amperage is so tiny that it is harmless. The spark that you get when you slide
across the car seat is several thousand volts, but less than one ten-thousandth
of an amp, which is why the spark does not cause you any damage. That is
also the case with your television set. The electric field in front of the
television screen is high voltage and low amperage, making it perfect for lighting
the fluorescent bulb, and safe for you at the same time.
The reporter was using the high voltage, low amperage electric field around
the wires to light the bulb, instead of using a gauss meter to measure the
magnetic field. It made dramatic television, but they were not demonstrating
what they thought they were.
Have a wonder filled week.
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Robert Krampf's on-the-road schedule:
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times, schools, etc. at http://www.krampf.com/m_tour.html
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http://www.krampf.com
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
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