Sam- This could be the starting idea for a good project. What you are
really asking here is whether the temperature (T) of the wire in the
ammeter affects how easily current can flow through it. In other words,
you're asking if T affects the resistance, R.
There are a few problems with your first plan. The resistance of
an ammeter is deliberately made very low, so you don't want to connect
them directly to a battery, which also has a low internal resistance.
The current will be huge, and will drain the battery even if nothing
gets fried. Also, the wires in the ammeter are out of reach, so it's
hard to change their T, and you don't know what they're made of, so the
interpretation would be difficult. Sending that much current through
the wire and battery will almost certainly heat one or both of them up,
making it hard to control and measure the temperature.
Why not mkae some coils of different types of wire and simply
measure their resistance with an ohmmeter at different temperatures?
You can see whether current flows more easily in hot or cold wires. You
could try to do the same thing with salt water. You could check how
much difference T makes for different types of wires, and see if any
important patterns emerge.
I should let you know that many such experiments have already been
done, and the results are well understood, and have provided lots of
information about the electrical properties of materials. That may be
fine- I don't know if your science fair requires new work or encourages
students to explore any project new for the student.
Mike W.
(published on 10/22/2007)
