Exam 6: Some Processes Are Irreversible Thermal Physics

A heat engine produces $300 \mathrm{~W}$ of mechanical power while discarding $1200 \mathrm{~W}$ into the environment (its cold reservoir). What is this engine's efficiency?

$10^{62} / 10^{60}=100$ . What is $\ln 10^{62} /$ In $10^{60}$ ? (Select the closest response.)

Consider each of the following processes. Is the process consistent (C) or inconsistent (D) with the limitations on equation T8.12 $d S=\frac{d Q}{T}$ (that $N$ be fixed and that the process not involve any energy transfer that is neither heat nor work due to a quasistatic volume change)? -c) A pan of water boils on the stove.

A mole of iron has about half the mass of a mole of silver. Which likely has the greater heat capacity?

Suppose that the forces holding an atom in its position in a crystal are the same for two different monatomic solids, but the mass of an atom $m$ is larger for solid $B$ than for solid $A$ . Which has the larger value of $T_{E}$ ?

Suppose that we have two containers, one holding $N$ molecules of helium gas, and one holding $N / 2$ molecules of oxygen gas. Both are initially at room temperature. We then add the same amount of energy to each gas. Which is hotter at the end?

A refrigerator uses $100 \mathrm{~W}$ of electric power and discards $600 \mathrm{~W}$ of thermal power into the kitchen. What is its coefficient of performance?

(b) The average molecular speed is zero.

Which of the following devices are heat engines? In each case, answer T (True) if it is a heat engine, and F (False) if it is not. -(a) Your body

An atom of helium can store energy by bumping an electron from its lowest orbital energy state to a higher orbital energy level. In particular, moving an electron from the lowest state to the next-lowest state would store an energy of $24.6 \mathrm{eV}$ . Why can we ignore this energy storage mode when calculating the heat capacity of helium gas?

Doubling the number of effective opaque layers in a planet's atmosphere from $n$ to $2 n$ will make its average surface temperature increase by what factor?

Which of the systems listed below is the largest, having $N_{A}=N_{B}$ and $U=6 N_{A} \varepsilon$ for which there is a better than 1 in a billion chance of seeing one or the other solid having zero energy? (Hint: Using StatMech to check cases is probably the easiest approach.)

How does the number of molecules with speed $v\left\langle v_{P}\right.$ compare to the number having speed $v>v_{P}$ ?

As a normal object's thermal energy $U$ goes to zero, the slope of a graph of its entropy $S$ versus $U$

Consider a rectangular book. The book is (approximately) symmetric for rotations around an axis that goes diagonally from one corner to the other

All irreversible processes involve -(a) macroscopic objects,

As the temperature difference between its reservoirs increases, the COP of a refrigerator

Consider a system whose multiplicity is 1 , no matter how much energy one puts into it. What is such a system's temperature?

Problems T7T. 3 through T7T. 7 refer to the following cyclic gas process: -In static equilibrium, any excess charge on a conductor is uniformly spread on its surface.

In each of the processes described below, energy flows across the boundary of the object that serves as the subject of each sentence. Is this energy flow heat (A), work (B), or some other kind of energy transfer (E)? -(b) You get cooler when standing in the breeze from a fan.