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lecture27 - Ch. 12 Temperature and Heat 12.1 Temperature p...

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Ch. 12 Temperature and Heat 12.1 Temperature What is Temperature ? It is a measure of how “hot” something is. We use Thermometers to measure the temperature of something. Most rely on the fact that materials expand when heated. There are several different temperature scales. The two most commonly used are Fahrenheit and Celsius : Celsius Fahrenheit Boiling point of water 100 o C 212 o F Freezing point of water 0 o C 32 o F Between the freezing and boiling points, we have 180 o F and 100 o C. Thus, 100 o C = 180 o F. Relative to the freezing point, then: F C 1 o 5 9 o =
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9 5 o o 32) - F ( C = 32 C F o 5 9 o + = 12.2 Kelvin Temperature Scale The Kelvin temperature scale was introduced by a Scottish physicist, Lord Kelvin, in the late 1800’s. The Kelvin (K) is the SI unit of temperature. From the Ideal Gas Law at constant volume, RT V nRT nRT PV = P V = If P increases, then T must also increase to keep V constant, and vice versa. P Regardless of the gas, the temperature always extrapolates back to -273.15 o C at zero pressure. This defines the absolute zero point for a T temperature measurement. -273.15 o C This is Absolute Zero and it = 0 K. C -273.15 K 0 o =
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Nothing can get colder than absolute zero (0 K). Converting between Kelvin and Celsius: 15 . 273 o + = T T C K Celsius Kelvin Freezing Point 0 o C 273.15 K Boiling Point 100 o C 373.15 K Room Temperature 27 o C 300 K You should read section 12.3 on Thermometers . 12.4 Thermal Expansion Most solids expand when heated: Heat a thin metal rod, and it expands. or small changes in temperature For small changes in temperature, o L L Δ T L L o Δ Δ α is the Coefficient of Linear Expansion.
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Units on α ?[ 1 / o C] So, Δ T
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This note was uploaded on 08/04/2009 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.

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lecture27 - Ch. 12 Temperature and Heat 12.1 Temperature p...

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