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

In summary, the unit discussed is micrometers per millikelvin and represents absolute thermal expansion for a fixed length. This unit may be 'cancelled' for mathematical purposes, but it helps to make sense of the underlying information. Dimensional analysis is a useful method for checking the validity of answers, especially in unfamiliar situations.
  • #1
kasnay
10
1
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?
 
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  • #2
So that would be an absolute thermal expansion for a fixed length, not as a proportion of length.
 
  • #3
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)
 
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  • #4
okay thank you, well now my question is why did they bother putting it there if it could be cancelled?
 
  • #5
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.
 

1. What is the thermal expansion coefficient?

The thermal expansion coefficient is a measure of how much a material's dimensions will change when its temperature changes. It is typically represented by the symbol α and is expressed in units of length per unit temperature.

2. What do the units m/mK mean?

The units m/mK stand for meters per meter per Kelvin. This unit is used to represent the thermal expansion coefficient and indicates the amount of length change per unit length, per unit change in temperature.

3. How is the thermal expansion coefficient measured?

The thermal expansion coefficient can be measured by subjecting a material to different temperatures and measuring the resulting change in length or volume. This can be done using specialized equipment such as a dilatometer or by using mathematical equations to calculate the coefficient based on known properties of the material.

4. Why is the thermal expansion coefficient important?

The thermal expansion coefficient is important because it affects the dimensional stability of materials when they are exposed to changes in temperature. This can have practical implications in various industries, such as construction, where materials need to be able to withstand temperature changes without warping or breaking.

5. How does the thermal expansion coefficient vary between materials?

The thermal expansion coefficient varies between materials and can be influenced by factors such as the material's chemical composition, crystal structure, and temperature range. Generally, materials with stronger bonds between atoms, such as metals, tend to have lower thermal expansion coefficients compared to materials with weaker bonds, such as polymers.

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