Ask A Scientist© Engineering Archive

Index Key:   ENG047
Author:      maria c paoletti
Subject:     Metal expansion rates.
I am doing a science fair project on the expansion rates of three different
metals: copper, aluminum and galvanized steel.  I was trying to make a
hypothesis but I could not find any information on how much these metals
expand.  Can anyone help me find some information?  Also, I got some wire
made of the given metals and I would like to know if a home electric oven
would make a very noticeable change when the wire expands. The wire is 18
gauge.

Response #:  1 of 1
Author:      edward p barth
I assume that the expansion rates that you are asking about are thermal
expansion rates, in other words, the change in length per degree of tempera-
ture.  The valuer for metals are around 10 x 10^-6 per degree centigrade or
about one thousandth of a percent change per degree.  You can find the exact
numbers in a book called the Handbook of Chemistry and Physics, which your
public library should have.  Finding a number for galvanized steel will be
hard, especially if you do not know the type of steel or the thickness of
the coating.  But that is what makes this an interesting experiment!  In
your home oven, you might be able to raise the temperature by about two
hundred or two hundred fifty degrees centigrade.  That will give you a
length change of about a quarter or fifth of a percent.  That would be less
than a thirty second for an inch on  a ten inch piece for wire.  That is
possible, but you will have to be either very careful or clever.  (Hint:
Does the wire have to be straight?)  I hope your experiment works out well.