Science Buddies: "Ask an Expert"

My science fair project uses a 6 volt battery, an electrolyte, and copper wire. Insulated copper wire is run from one terminal of a 6 volt battery to a thin uninsulated copper wire that is in the shape of a coil (spring) The end of the coiled spring wire is lowered
just below the surface of an electrolyte solution made up of distilled water and dissolved purified salt. Another insulated copper wire is run from the other terminal of the 6 volt battery and it's other stripped bare end dipped in the elctrolyte solution. This should
cause the spring to contract on itself as it ends become the opposite poles of an electromagnet. When the spring contracts, the circuit would be broken causing the magnetic effect to cease and the spring to relax and dip back into the electrolyte solution. The
process would repeat itself causing the "spring" to jump up and down. I am unable to get this to happen. The 6 volt battery is new,
the wires are connected well, the electrolyte has all the salt that will dissolve in it, the coiled wire is the thinnest wire I could find.
Any suggestions?

Thanks,

T.A.

Hello and welcome to the forum:

This is an interesting experiment - could you post a link to its description (if there is one)? Thanks.
First, I wonder why you are using uninsulated wire for the spring? This seems unnecessary, and could contribute to the failure if the coils short out to each other. In this case there would be no electromagnet effect.

Could you please place an ammeter in the circuit with the wire so we can know how much current flows? I would suggest the following tests: Connect one lead of the battery to the ammeter, the other ammeter lead to a wire placed in the electrolyte, another wire from the electrolyte to the other battery terminal. Just hook this up long enough to get a reading on the ammeter, as it will draw a lot of current if everything is working. Then add the spring (insulated) and see what the current is. You may need to make your spring from a lot of wire to get its resistance up enough so that you don't immediately discharge your battery

Let us know how this works.
Keith

You say that you are using uninsulated wire for the spring. Are you actually using "magnet wire," the kind of wire that has a thin coat of varnish on it? If so, then the varnish will insulate it. Be sure you have truly uninsulated wire.

Queen E - This is an interesting experiment and is based on the fact that energizing the coil with a DC current will create an attraction between the turns and thus cause the coil to become slightly 'shorter'. Because the tip of the coil was just touching the conductive electrolyte solution, in the 'relaxed' state current would flow. As the coil shortened, the tip would retract from the electrolyte and break the circuit. There is a small delay in time as the un-energized coil tip went back to it's position in the electrolyte, completing the circuit again. This creates an oscillation that can be observed as the tip of the coil makes and breaks electrical contact. This type of action is called a 'relaxation oscillator'. You can research more about that on the web. While I didn't locate this experiment in the Science Buddies literature, I did find a reference for the same phenomenon in a 1941 Popular Mechanics magazine on the web. This experiment used a small pool of mercury which acted as the conductive liquid similar to your electrolyte. Go to page 115 of the magazine for a description and illustration. This article used #26 steel wire. A link to the entire edition of the magazine is attached. You might find it interesting as it is 70 years old.

Rick Marz

http://books.google.com/books?id=htkDAA ... &q&f=false