lecture22

# lecture22 - Phys 2101 Gabriela Gonzlez Zeroth law of...

This preview shows pages 1–4. Sign up to view the full content.

1 Phys 2101 Gabriela González 2 Zeroth law of thermodynamics : If bodies A and B are each in thermal equilibrium with a third body T, then they are in thermal equilibrium with each other. Or: every body in thermal equilibrium has a well defined “temperature”. When two bodies have the same temperature, they are in thermal equilibrium.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 3 On small scale, temperature is a measure of the vibration of the atoms in the material (solid, gas or fluid). SI unit: kelvin (K) There is an absolute minimum temperature (when all the atoms are still). That temperature is zero kelvin. There is a special temperature at which ice, water and vapor coexist: “triple point of water”. This temperature is defined as 273.16 K. Other common scales: Celsius ( o C): T c =T-273.15. ice-water temperature =0 o C, boiling water =100 o C. Fahrenheit ( o F): T F =(9/5)T C +32. (0 o F=brine temperature; 100 o F~human body temperature) a) Normal Body temperature is 98.6 o F. What is it in kelvins and o C? b) Comfort level is usually accepted to be 68 o F. What is it in kelvins and o C? Fahrenheit, Daniel Gabriel (1686-1736) Lord Kelvin (1824-1907) Anders Celsius 1701-1744 T c =(98.6-32)*5/9=37 o C T k =37+273.15=310.15 K T c =(68-32)*5/9=20 o C T k =20+273.15=293.15 K 4 When temperature changes, solid bodies change their length, and all bodies change their volume according to: Δ L = L α Δ T with α = coefficient of linear expansion Δ V = V β Δ T with β = coefficient of volume expansion If a body has a length L 0 at temperature T 0 , what is its length at a temperature T? L(t) = L 0 + Δ L = L 0 +L 0 αΔ T = L 0 (1+ αΔ T)
3 5 A highway is made of concrete slabs that are 15m long at 20 o C. (a) If the temperature range at the location of the highway is from -20 o C to +40 o C, what size expansion gap should be left (measured at 20 o C) to prevent buckling of the highway? Concrete has a coefficient of linear expansion

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 12/01/2011 for the course PHYS 2101 taught by Professor Grouptest during the Fall '07 term at LSU.

### Page1 / 6

lecture22 - Phys 2101 Gabriela Gonzlez Zeroth law of...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online