MasteringPhysics17b

# MasteringPhysics17b - MasteringPhysics: Assignment Print...

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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI. .. 1 of 10 12/19/2007 1:03 PM [ Print View ] PHCC 141: Physics for Scientists and Engineers I - Fall 2007 17b. Temperature and Heat Due at 11:59pm on Monday, November 12, 2007 View Grading Details Conduction of Heat Understanding Heat Conduction Learning Goal: To understand the heat conduction formula and the variables in it. Conduction--the flow of heat from a hotter object to a cooler object or from a hotter region to a cooler region of the same object--is the most common mechanism of heat transfer. The formula governing this is . Part A This formula applies to ________________. ANSWER: any object of cross-sectional area ; length ; and thermal conductivity any object of cross-sectional area ; length ; and thermal resistivity a plate of surface area ; long dimension ; and thermal conductivity a plate of surface area ; long dimension ; and thermal resistivity This formula gives the heat conducted at steady state by any object of uniform heat conductivity and cross-sectional area, whose hot and cooler ends are at and , respectively. Typical examples are a wire, rod, or an insulating layer, the latter of which will typically have a large area and relatively short length (thickness) . Imagine that you are applying the heat conduction formula to a rod that is held at a high temperature on one end and at a low temperature on the other end. Indicate whether the following statements are true or false. Part B The quantity is the rate of heat transfer from the hot to the cold end of the rod. ANSWER: true false Part C The quantity is the rate of heat added to the hot end of the rod to maintain its temperature. ANSWER: true false Part D The quantity is the rate of heat removed from the cold end of the rod to maintain its temperature. ANSWER: true false Part E

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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI. .. 2 of 10 12/19/2007 1:03 PM The quantity is the total amount of heat transferred from the hot to the cold end of the rod. ANSWER: true false The flow of heat into, through, and out of the rod are equal under steady state conditions in which the temperature of each end of the rod is constant. The heat conduction formula applies only in steady state; it does not apply to the situation in which one end of a bar is suddenly placed in a flame while the other end is held at fixed temperature (as in an ice bath); the formula would only apply after the temperature at every point in the bar had reached a steady-state value. Part F In the SI system of units, what are the units of the quantity ? ANSWER: joules amperes watts Heat Flow through Three Rods Three identical rods are welded together to form a Y-shaped figure. The cross-sectional area of each rod is , and they have length and thermal conductivity . The free end of rod 1 is maintained at
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## MasteringPhysics17b - MasteringPhysics: Assignment Print...

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