10thermal

10thermal - 11/19/2010 Temperature Temperature is that...

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11/19/2010 1 Temperature Temperature is that property of a body of matter that gives rise to sensations of hot and cold; it is a measure of average molecular kinetic energy. Heat is molecular kinetic energy. The color of an object hot enough to glow varies with its temperature roughly as shown here. Thermometers A thermometer is a device for measuring temperature. In the Celsius scale, the freezing point of water is given at the value of 0°C and the boiling point of water the value 100°C. In the Fahrenheit scale, these temperatures are given the values 32°F and 212°F. Thermometer Applications A liquid-in-glass thermometer: Mercury or a colored alcohol solution responds to temperature changes to a greater extent than glass does, and so the length of the liquid column is a measure of the temperature of the thermometer bulb.

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11/19/2010 2 Temperature scales: Common temperature scales are: Fahrenheit (F), Celsius (C ), and Kelvin (K). T C = 5/9 (T F 32) T F = 9/5 T C + 32 T K = T C +273 Exercise: At what temperature will the Fahrenheit and Centigrade scales yield the same numerical value? Exercise: When heat is added to boiling water, the water temperature (a) increases (b) decreases (c) stays the same (d) none of these. Comparison of the Celsius and Fahrenheit temperature scales. Thermal Expansion The change in physical size (length, area or volume) of a substance when its temperature changes. For most substances, the physical size increases with an increase in temperature and decreases with a decrease in temperature Joints such as this one are used in bridges to accommodate thermal expansion.
11/19/2010 3 Thermal Expansion Linear expansion: Δ L = α L o Δ T α : the coefficient of expansion, unit o C 1 Volume expansion: Δ V = β V o Δ T β : the coefficient of expansion, unit o C 1 Examples: α AL = 25 × 10 6 ( o C) 1 β AL = 75 × 10 6 ( o C) 1 α Glass = 9 × 10 6 ( o

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This note was uploaded on 11/22/2010 for the course PHYS 1146 taught by Professor Balasubramamaheswaran during the Spring '10 term at Northeastern.

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10thermal - 11/19/2010 Temperature Temperature is that...

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