P P A6 Concep Tests Ch 15
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- 2. ConcepTest 15.1 Free Expansion A free expansion occurs when a valve is opened allowing a gas to expand into a bigger container. In such an expansion the temperature of the gas will: 1) increase 2) decrease 3) stay the same
- 3. ConcepTest 15.1 Free Expansion A free expansion occurs when a valve is opened allowing a gas to expand into a bigger container. In such an expansion the temperature of the gas will: 1) increase 2) decrease 3) stay the same In such a process: W = 0 there is no object to move, Q = 0 there is no heat exchange, therefore U = 0 by the First Law of Thermodynamics. Thus, there is no change in the temperature. Free expansion is neither adiabatic nor isothermal expansion, even though T and Q are zero. Free expansion is an irreversible process --- the gas molecules have virtually no chance of returning to the original state.
- 4. ConcepTest 15.2 Work In the closed thermodynamic cycle shown in the P-V diagram, the work done by the gas is: 1) positive 2) zero 3) negative V P
- 5. ConcepTest 15.2 Work In the closed thermodynamic cycle shown in the P-V diagram, the work done by the gas is: 1) positive 2) zero 3) negative The gas expands at a higher pressure and compresses at a lower pressure. In general, clockwise = positive work; counterclockwise = negative work. V P
- 6. ConcepTest 15.3 Heat Engine The heat engine below is: 1) a reversible (Carnot) heat engine 2) an irreversible heat engine 3) a hoax 4) none of the above
- 7. ConcepTest 15.3 Heat Engine The heat engine below is: 1) a reversible (Carnot) heat engine 2) an irreversible heat engine 3) a hoax 4) none of the above Carnot e = 1- T C / T H =1-270/600=0.55. But by definition e = 1- Q L / Q H =1 - 4000/8000=0.5, smaller than Carnot e , thus irreversible. Follow-up: What would you need to change to make it a Carnot engine?