Location:
Concepts Shown:
A true Gee Whiz experiment that demonstrates luminescence by running a current through a pickle, which causes it to glow.
Equipment:
2 aluminum strips (electrodes) 0.25" x 3" x 1/6" (equivalent, or use long nails), 2 18" insulated wires, 12"x12" x3/4" fire retardant ply-wood (or equivalent substitute), extension cord, alligator clips, 3 1.5" nails, 2 wood screws and washers, Variac Variable Transformer, Dill Pickle, Fire retardant paint (black grill paint).
Procedure:
Construction:
Paint the wood with the grill paint. Cut the female end off the extension cord, and attach the alligator clips to the end of the extension cord.
Pound 3 nails straight, from the top across the middle, one in the center, two on each side. Put them in so about half the nail is still up. Strip the ends of the wire and attach one end to the aluminum electrode using either solder or electrical tape. Attach the other end to a side nail. Secure the middle of the wire down to corners opposite of each other, using the screw. Make sure that the electrodes can not touch each other or the center nail.
Presentation: Plug the alligator clip wire into the transformer, and connect the clips onto the nails. Place the pickle on the center nail, and stick the electrodes into the pickle, but not all the way through. Make sure they are fairly secure in the pickle. Turn the transformer on and turn it up to about 140V. The pickle will light up, leave it in this state for about 20-30 seconds.
Science:
The most important concept to be taught here is that of electroluminescence. The exact reason for the orange glow in the pickle is not completely known as of yet, but it can be most likely attributed to one of two things:
1) The sodium atoms from the salt (NaCl) used in the pickling process are excited up to a higher energy state by the electric current. As the electrons decay to lower more stable states they give off the photons associated with orange light. Orange light has a wavelength of 600-650nm, which the wavelength associated with the photons given off by sodium electrons.
2) A less accepted, yet still possible explanation, is that the sodium ions combine with the acids in the vinegar and form a gas which is then ignited by the electric current and gives off the orange light. Note, during the experiment only 1/2 of the pickle lights up. There is no way to predict which side will light up, and as well there is no clear explanation for it. At this point the most reasonable explanation would be, since and AC current is sued, that the pickle is polarized in an initial direction. Once this initial polarization occurs, it can not be overcome by any other change in the current direction. Other: Take extreme caution with this experiment, live electricity is dangerous. Also be prepared for a somewhat offensive smell, and don't be surprised if you see steam coming from the pickle. Another idea, pickle your own pickles using different salts (CuCl), but be careful they would be deadly to eat.
References:
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