You are in luck!!!! Here is an experiment that involves a lemon that forms part of a battery.
one lemon, a copper penny, strip of zinc (you can get this from a
hardware store), steel wool, a knife, and a current meter (measures the
current flowing in the circuit).
TO DO: Use the steel wool to
shine the surfaces of the penny and the zinc strip. File down any sharp
edges on the zinc strip. Have an adult use the knife to punch two small
slits into the lemon's skin. The slits should be about a 1/2 inch long
and should be 1/4 inch apart.
Insert a penny into
one of the slits. Insert the zinc strip into the other slit. Make sure
the metals don't touch! Touch the leads of the current meter to the
exposed metals. Voila!!!! The needle in the current meter moves. Can
you explain why?
More information: Here's a bit of an
explanation for why this battery works. The two different metals
(copper and zinc) don't dissolve equally well in the acidic lemon
juice. Positively charged ions (Zn+2) come off the zinc and go into
solution, so long as there is a way for the negatively charged
electrons left behind to flow out of the zinc metal to the copper.
There they pull positive hydrogen ions (H+) out of solution. The
electrons' route is provided by the external circuit, which includes
the current meter. When two H+'s combine with two electrons from the
copper, they form a neutral hydrogen molecule. Both pieces of metal
stay nearly neutral, but negative electrons flow through the wire from
one to the other and positive ions flow through the lemon from one
toward the other.
As the electrical current travels through the
external circuit, it makes the meter's needle deflect. It does that via
magnetic forces, because the current flows through a little coil in the
meter, making a magnetic field.
Something else:::: See if other
metals can do the came thing. Try some aluminum for example, replacing
the copper or replacing the zinc. Does it do the same thing?????? :)
And try using the same metal at both ends. If our explanation is right,
that shouldn't give any current.
(published on 10/22/2007)