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Warm-Up Exercise for lecture 23

Due 8:00 am, Tues, 17 Nov 2009

Physics 105, Fall 2009

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Did you complete the reading assignment? (Typically this means at least 20-30 minutes looking over the assigned sections of the book.)
yes no

A gas has its pressure reduced while its volume is kept constant. What does this look like on a PV diagram?
a horizontal line going to the right
a horizontal line going to the left
a vertical line going up
a vertical line going down

Same situation. How did the temperature of the gas change during that process?
the temperature increased
the temperature decreased
the temperature stayed the same
the temperature change cannot be determined from the information given

The second law of thermodynamics says for a heat engine:
You get more work energy out than you put in as heat
You get the same work energy out as you put in as heat
You get less work energy out than you put in as heat

Ralph is confused because he knows that when you compress gases, they tend to heat up. Think of bicycle pumps, for example: compressing the air heats up the nozzle of the pump. Yet section 12.3 (8th edition) talks about "isothermal" processes where the temperature doesn't change. How are such processes possible?  How can you compress a gas without its temperature increasing?

The comments in the next next two boxes go into a big, mostly anonymous text file that I skim through before the morning lecture, using the comments to help me plan class discussion. ("Mostly anonymous", because I can track down who made what comment, but it takes some effort on my part to do so.) Therefore, if you really want to make sure I see your question/comment and answer it individually, you should send it to me via email and not through this form.

Which part of today's assignment was particularly hard or confusing? What would you like to spend extra time on in class?

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