Sean H. Breheny wrote, in part:
>[much deleted for brevity]
>Note, too, that this actually
>shows area expansion to be a nonlinear function of deltaT, even if linear
>expansion is a linear (no pun intended) function of deltaT.

By definition, all the coefficients of thermal expansion (whether for
length, area, or volume) are for linear changes. Same idea as
resistance, where the definition is V = I R, whether or not the
potential actually varies linearly with the current; in cases where
the variation *is* (to a good enough approximation) linear, R is a
constant and is called the resistance. The derivation I gave is
correct, because the coefficients are *defined* for the linear regime
(in which change in size is proportional to change in temperature).
In that regime, the coefficient of area expansion is exactly 2 times
the coefficient of length expansion.

Nonlinear effects can also be treated, of course, to as high an
order as you need to go to get the precision that you need.

Michael

Thank you for reading my little posting.


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