7b-midterm1-sol-key summer 2011

# 7b-midterm1-sol-key summer 2011 - Physics 7b Summer 2010...

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Physics 7b Summer 2010 – Midterm 1 – Solutions I. PROBLEM 1 (a) γ monatomic = C P C V = C V + R 3 / 2 R = 5 3 , γ diatomic = C P C V = C V + R 5 / 2 R = 7 5 4 pts total. (b) Solid line indicates monatomic gas, dashed is diatomic. 6 pts total. (c) The PV diagrams are not equivalent. Larger γ means a steeper adiabat, and given the constraints more area within the curve. So, more work is done per cycle by the monatomic gas. 6 pts total. (c) The e ciencies are the same given that the e ciency of a Carnot cycle is determined solely by the high and low operating temperatures. 4 pts total.

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II. PROBLEM 2 (a) Δ Q Δ t 1 = kA Δ T l V 1 = Al V 2 = 4 Al 2 l 2 = l 4 Δ Q Δ t 2 = k 4 A Δ T l 2 = 16 kA Δ T l = 16 Δ Q Δ t 1 Δ t 2 = Δ t 1 16 = 1 . 875 minutes 13 pts total (b) Δ S = Q T , Q = mL water , T = const = T mixture , Δ S = mL water T mixture = 1 kg × 333 kJ / kg 273 . 15 K 1 . 22 kJ / K 7 pts total III. PROBLEM 3 P a V γ a = P b V γ b ( P a V a ) γ
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## This note was uploaded on 08/02/2011 for the course PHYS 7B taught by Professor Huang during the Summer '11 term at University of California, Berkeley.

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7b-midterm1-sol-key summer 2011 - Physics 7b Summer 2010...

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