## Saturday, December 12, 2009

### Thermal Physics Test for skeptics

Way too many blockheads, morons, idiots and ignoramuses are spouting off non-stop on human-induced global warming, insisting it is all fabricated. Most of these have never taken a physics course in their lives, most noted when they refer to water vapor as a greenhouse gas on a par with CO2, while failing to point out:

a) Even a tiny, minuscule amount of CO2 is vastly more efficient at blocking the re-radiation of energy than any amount of water vapor- at the appropriate (molecular) spectral bands

b) the misconception arose because early researchers, lacking the current technology of infrared spectroscopy, assumed that water vapor bands already blocked out most of what would (ordinarily) be taken by CO2.

c) Water vapor as a pernicious greenhouse gas does not and will not "kick in" until most CO2 has been outgassed from carbonates

With that in mind I offer this basic proficiency test to any global warming deniers with the cojones to take it. If you score at least 70% on it, I will concede you have the unmitigated right to offer your input on the subject - are at least minimally qualified to do so, and are not in the goober category. That is, you also have the right and expectation to be taken at least half-way seriously. Below 70, you are a clown. Don't take it at all, you are still a clown because you know you'd be wasted.

Answers may be supplied via the blog comment feature and the working required ought to fit in there too.

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In each case, either solve the problem as given, or provide the correct answer (A, B, C , D or E) for multiple choice:

1) An air conditioner has a power rating of 1.0 kilowatt. A solar panel on the roof of a house has a collective efficiency of 12% and is 5 meters by 5 meters. The solar power (insolation) constant is 1360 watts per square meter. Assuming the ac will be run from 11 a.m. to 4 p.m. , will the panel be able to achieve the objective? Assume no cloud cover, and no significant variation in insolation. Show all working.

2) A hot air balloon of constant volume contains air at 100 C. The fraction of this air which escapes if the temperature is increased by 1 K (Kelvin) – the pressure remaining constant is:

A) 1/ 373 B) 1/ 273 C) 1/ 100 D) 374/373 E) 101/100

3) The first law of thermodynamics is often stated in the form: Q = DU + W. Which of the quantities, Q , DU or W must necessarily be zero when a real gas undergoes a change at constant pressure?

A) Q only B) DU only C) W only D) none of DU, Q, W E) all of DU. Q, W

(Note Q denotes heat added, W is work done, and DU denotes change in internal energy)

4) Two identical copper calorimeters of mass 0.1 kg contain 1 kg of water and 2 kg of alcohol, respectively. It’s found that they both take 60 minutes to cool from 350 K to 300 K under similar conditions. Find the specific heat of the alcohol (in J/ (kg K) ) based on this information:

A) 600 B) 2060 C) 2100 D) 2140 E) 3800

5) Which of the following statements about temperature is NOT true?

A) It represents the amount of heat contained in the body.
B) It is a measure of degree of hotness or coldness of a body
C) It is a property that determines the direction of heat flow in a body.
D) It is a measure of the average kinetic energy of the particles of which it’s composed.
E) It may be measured by examining the length of a column of mercury.

6) A detector of thermal energy is placed an equal distance in turn from each of four faces of a hollow metal cube full of water. The reading on the detector is greatest when the face is turned toward the face that is:

A) painted silver B) painted shiny white C) painted dull black
D) highly polish E) neither of the faces makes any significant difference

7) A bottle of water is placed in the freezer of a fridge and forgotten. It’s recovered after 24 hrs. and found to be broken. The reason for breakage is:

A) the bottle expanded as it cooled B) water expanded more than the bottle as it froze C) the bottle contracted as it cooled D) the water contracted as it froze
E) the water and bottle both expanded as they cooled

9) The diagram below shows two bodies of equal mass (A and B) within a thermally insulated material. A has a thermometer inserted to take readings. A was initially at a temperature of 100C and B at 50 C when placed in thermal contact.

[ [A][B] ]

a) Find the temperature of the system of two bodies in thermal equilibrium. Is this the same as the reading of A’s temperature? (Show work, explain)
b) Which body undergoes a positive change in entropy?
c) Which body undergoes a negative change in entropy?
d) What is the total entropy change for the system, A + B?

10)a) Describe the principle of operation of a basic, glass-enclosed greenhouse. What specific features enable more heat to be collected within than available from the immediate, outside environment?

b) One kilogram of mercury is initially at 0 C. Find its change in entropy when heat is slowly added to raise its temperature to 100 C.

Data: Heat of fusion for Hg = 1.17 x 10 4 J/ kg, specific heat (Hg) = 138 J/ kg C; Melting temperature (Hg) = -39 C)

Specific heat (H2O) = 4,200 J/ kg C

Marking scheme: Problems 1 through 8, 8 marks each. Problem 9: 16 marks ; Problem 10: 20 marks

Total 100 marks:

Score 90-100 is ‘erudite master of global warming-climate theory’

Score: 80-90: You have a decent knowledge of climate-based physics - opine at will!

Score 72-80 Needs to bone up! But hey, knock yourself out on your opinionating!

Score 70-72: I give you a pass. Barely! Just keep your opinions on global warming to 100 words or less.

Less than 70 = poseur and/or PR shill for Oil-gas lobbies. Don't bother to write ONE word on global warming!