# Warm-Up Exercise for lecture 23

## Due 8:00 am, Tues, Nov 18

Physics 105, Fall 2008

The work done by a gas when expanding can be calculated by:
☐ the area under the curve representing the process in the P-T diagram
☑ the area under the curve representing the process in the P-V diagram
☐ the area under the curve representing the process in the T-V diagram

The first law of thermodynamics is a statement of:
☑ conservation of energy
☐ conservation of (regular) momentum
☐ conservation of angular momentum
☐ conservation of mass

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 in class Dr. Colton mentioned that when you compress gases, they tend to heat up. (Think of bicycle pumps.) Yet section 12.3 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?

Just take away some heat at the same time, by (for example) surrounding the gas with something cold.