Krampf Experiment of the Week -
#63 The Versorium
http://www.krampf.com
I was digging through my files for the electricity summer
camp and came across this experiment that I thought you would enjoy.
Most of us have had experience with static electricity, even here in
humid Florida.
While we hear it crackle when we take the clothes out of the drier (and
see if too if the room is dark. Try it!!), and we feel it when we put
our hand near the TV screen, there are often static charges around us
that are too weak for our senses to detect. The versorium is one way
that we can detect them.
For this experiment, you will need:
* a plastic soda straw
* about 2 feet of thread
* tape
* objects made of different materials (glass,
plastic, wood, etc.)
Tie one end of the thread around the middle of the straw. Use a piece
of tape to secure the other end to the side of a table, so that the
straw hangs down and swings freely. It should not be near the leg of
the table. Now, take one of the objects that you have gathered. A
plastic pen is a good place to start. Rub the pen against a piece of
cloth. Now hold it near your hand. Do you feel anything? Probably not.
Now, bring the pen close to the straw and watch carefully. If you have
produced a static charge, then the straw should swing towards the pen.
If it does not, then dry the pen and the cloth with a hair drier and
try it again.
Try lots of different things. Try a pen rubbed with paper, with hair,
with leather, with wood, etc. Try rubbing two pens together. Do two
objects made of the same material produce a static charge?
What is going on? Well, when you rub two different materials together,
one will lose electrons and have a positive charge. The other will gain
electrons and have a negative charge. In some ways, static charges are
like magnetic charges. Two charges that are different will attract.
Charges that are the same will push apart or repel. If you bring a pen
that is negatively charged near the straw that is not charged,
something neat happens. The negative charges in the end of the straw
are pushed away (like charges push away), leaving a positive charge on
the end of the straw. Opposite charges attract, so the positive charge
on the end of the straw is pulled towards the negative charge on the
pen.
The versorium does not identify positive and negative charges. Either a
positive or a negative charge will attract the straw. It does show that
a static charge is present, even if it is too weak for our senses to
detect. If you want to try the versorium on a larger scale, tie a rope
to a large board. An 8 foot 2x4 is impressive for this one. Suspend the
board, just as you did with the straw. Once it is balance, blow up a
balloon and rub it on your hair. Bring the balloon near the board and
it will swing to the balloon. Isn't science fun!!!