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Undergraduate teaching
July 15, 2011
Published by Bryan at July 15, 2011
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The more heat that is converted into work, the more efficient the process. The heat lost to the cold reservoir cannot be recovered. Efficiency is therefore define as the ratio of work out to heat in,...
July 13, 2011
Published by Bryan at July 13, 2011
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The Third Law of Thermodynamics says: if two separated systems are in thermal contact with a third, then at equilibrium they all have the same temperature.
Clearly when we bring two blocks together, heat will flow between them. This is an example of coupling systems A to B and to C so eventually the three will be in equilibrium. This coupling only allows heat to flow through direct contact.
July 11, 2011
Published by Bryan at July 11, 2011
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Suppose we have a system which is a drink in a glass. Certainly heat flows in and warms the cold drink, and mass changes when we add to the glass or drink the contents. The system is open.
June 30, 2011
Published by Bryan at June 30, 2011
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First it is never possible to obtain a true reversible path. It is an idealized case in which at every step along the way the system (the ball) is in equilibrium with its surroundings. Clearly if something is at equilibrium there is no noticeable change. Hence one says that a reversible process happens so slowly that equilibrium is always maintained.
June 16, 2011
Published by Bryan at June 16, 2011
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At a rate of 10% your money will double in 7 years . If you invest $1,000 in a tax free pension account at 10%, then after 35 years that $1,000 will have grown to $32,000!
June 6, 2011
Published by Bryan at June 6, 2011
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The time to reduce 4 beers to 2 is two hours. The time to go from 2 beers to 1 is one hour, and the time to go from 1 beer to the legal limit is 30 minutes. It therefore takes a whooping 3.5 hours to reach the legal limit: 4 beers take seven times longer to metabolize than 1 beer.
June 2, 2011
Published by Bryan at June 2, 2011
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Another way to ask the same question: suppose you have eaten all the food you need to keep your metabolism and daily activity going, but then you have one cookie too many. How much fat will that put on you?
May 4, 2011
Published by Bryan at May 4, 2011
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Let us suppose that you read somewhere that perfect pancakes should have a density of 0.7 g ml-1. How could you ensure that you cook the pancakes so that they come out with that density?
April 25, 2011
Published by Bryan at April 25, 2011
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The skin of the Earth rearranges in a cataclysmic event. As the Earth’s crust trusts and turns, tsunamis slosh around the globe and volcanic activity obliterates the sun causing rapid cooling. Such an event can happen over the period of a few days, as evidenced by the fast freezing of animals found with their tropical diet still intact in their bellies. Many species become extinct, and those pockets of human’s that do survive are thrown back to the Stone Age.
April 18, 2011
Published by Bryan at April 18, 2011
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What do hot chickens, pH of blood, bubbly drinks, coral reefs, and thermostating the Earth have in common? They all make use of one of the most basic processes in the Physical Chemistry: the equilibrium between carbon dioxide and carbonic acid.
April 16, 2011
Published by Bryan at April 16, 2011
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A song by Flanders and Swan recorded many years ago that explains the laws of thermodynamics very clearly
March 30, 2011
Published by Bryan at March 30, 2011
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In this third part on nuclear radiation I want to mention some of the biological effects. Although many agree that no level of radiation is safe, it really comes down to a matter of chance. Since negative effects of radiation increase with increased exposure, we should do what we can to keep radiation around us to a minimum.