Quiz03b-s

# Quiz03b-s - =600 g to bring it from T i = − 10 ◦ C to T...

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Quiz 3b Name: Date: Phys224 Spring 2010 Dr. P. Hanlet Concept (3 points each) 1. As shown in class, why is β = 3 α in the Chapter 20 equations? (a) because volume has 3 dimensions, so it is exactly 3 times larger (b) because of the molecular structure of matter (c) because it is an approximation in the cubic expansion for small Δ L (d) all of the above (e) none of the above 2. The following devices are used to deliver heat to the human body: (a) hair dryer (b) heat lamp (c) hot-water bottle By which respective mechanism does each transfer heat? (a) conduction, convection, radiation (b) conduction, radiation, convection (c) convection, conduction, radiation (d) convection, radiation, conduction (e) radiation, conduction, convection (f) radiation, convection, conduction 1

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Problem (5 pts) Show your work!!! If I can read it, I will give you partial credit!!! Correct answers without work will NOT get full credit. 3. How much heat must be absorbed by ice of mass m
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Unformatted text preview: =600 g to bring it from T i = − 10 ◦ C to T f =+25 ◦ C? • L V =2256 kJ/kg • L F =333 kJ/kg • c ice =2 . 05 kJ/kg/K • c liquid =4 . 18 kJ/kg/K • c gas =2 . 08 kJ/kg/K There are 3 successive stages of heating in this problem: (a) heating ice: Q i (b) changing phase: Q il (c) heating liquid: Q l So, the total heat required is: Q tot = Q i + Q il + Q l = mc i Δ T i + mL F + mc l Δ T l = m ( c i Δ T i + L F + c l Δ T l ) where I’ve redeFned c i = c ice and c l = c liquid . The values are predeFned. Additionally: • Δ T i =0 ◦ C − ( − 10 ◦ C )=10 ◦ C =10 K • Δ T l =25 ◦ C − ◦ C =25 ◦ C =25 K Substituting in values: Q tot = 0 . 6 kg ((2 . 05 kJ/kg/ a a K )(10 a a K ) + 333 . kJ/kg + (4 . 18 kJ/kg/ a a K )(25 a a K )) = 0 . 6 A A kg ( 20 . 5 kJ/ A A kg + 333 . kJ/ A A kg + 104 . 5 kJ/ A A kg ) = (0 . 6)(458 kJ ) ±inally: Q tot = 274 . 8 kJ 2...
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## This note was uploaded on 05/01/2010 for the course PHYS 224 taught by Professor Hanlet during the Spring '10 term at Illinois Tech.

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Quiz03b-s - =600 g to bring it from T i = − 10 ◦ C to T...

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