# Question about these thermal expansion coefficient units (m/mK)

• kasnay

#### kasnay

so I have never seen this unit before. 10^-6m/mK for the thermal expansion (linear expansion). I believe this unit is micrometers divided by mili kelvins?

So that would be an absolute thermal expansion for a fixed length, not as a proportion of length.

I believe it's:

meters / (meter x Kelvin) (not milliKelvin)

Simplifying ('cancel' the meters), it's just a ratio of expansion per degK (in one dimension)

berkeman and Chestermiller
okay thank you, well now my question is why did they bother putting it there if it could be cancelled?

It may be 'cancelled' for mathematical purposes. The information that it conveys helps you to make sense of what the number actually represents. In this case, 1 micron per meter of length for every 1 DegK. I don't know if they explicitly teach dimensional analysis these days, but it is a very useful way to check the validity of your answer - particularly if you're doing something unfamiliar.