Lecture17 - PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 17...

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PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 17
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Heat: Q = Energy transferred due to microscopic contact Heat can: Change temperature c = specific heat For water: c= 1.0 cal/(g°C) Change state of matter L = Latent heat of fusion or vaporization For water: L F =79.7 cal/g, L V =540 cal/g Recap - Heat Transfer Q = mc ! T Q = mL
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Example 11.11 A 50 g ice cube at 0ºC is put into a styrofoam cup containing 300 g of coffee at 90ºC. Assuming no heat is lost to the cup or the air, what is the final temperature of the coffee after the ice melts? T = 65.8°C
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Recap - Kinds of Heat Transfer Conduction Hot and cold objects in physical contact Examples: Heating a skillet, losing heat through the walls Convection Hot objects move (gas or liquid) Examples: Hot-water heating for buildings Circulating air Unstable atmospheres Radiation Energy transferred by light (UV, IR,…) Examples: Stars, Incandescent bulbs
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Conduction Rate of heat transfer Conductivity k is property of material R-value also depends on thickness. It adds for layered objects (R=R 1 +R 2 ) P = Q t = kA " # T / # x = A " # T / R R = " x / k
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Example 11.12 What is the ratio of heat transfer for a single pane
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Lecture17 - PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 17...

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