Question 1

Which law of thermodynamics is illustrated by the first image, where heat flows spontaneously from a hot object to a cold object?

Accepted Answer

The Second Law of Thermodynamics

Question 2

A monatomic ideal gas undergoes an adiabatic expansion. If the initial pressure is $$P_0 = 10.0$$\ \mathrm{Pa}$$, the initial volume is V_0$ = 40.0\ \mathrm{m}^3$$, and the final pressure is $$P_f = 2.00\ \mathrm{Pa}$$, what is the final volume $$V_f$$? (Use $$\gamma = \frac{5}{3}$$ for a monatomic gas.)

Accepted Answer

$$V_f = 105\ \mathrm{m}^3$$

Question 3

For a heat engine operating between a hot reservoir at temperature $$T_H$$ and a cold reservoir at temperature $$T_C$$, which equation gives the maximum possible efficiency?

Accepted Answer

$$e = 1 - \frac{T_C}{T_H}$$

Question 4

A refrigerator removes $$Q_C$$ amount of heat from the cold reservoir using $$W$$ amount of work. What is the coefficient of performance (COP) for the refrigerator?

Accepted Answer

$$COP = \frac{Q_C}{W}$$

Question 5

In the context of the second image, what does $$Q_H$$ represent?

Accepted Answer

The heat absorbed from the hot reservoir

Question 6

If a Carnot engine operates between $$T_H = 400\ \mathrm{K}$$ and $$T_C = 300\ \mathrm{K}$$, what is its maximum efficiency?

Accepted Answer

$$0.25$$

Question 7

Which of the following statements about entropy is correct?

Accepted Answer

The total entropy of an isolated system can only increase or stay constant.

Question 8

A heat engine receives $$Q_H = 2000\ \mathrm{J}$$ from a hot reservoir and expels $$Q_C = 1500\ \mathrm{J} to a $$cold reservoir. What is the efficiency of the engine?

Accepted Answer

$$0.75$$

Question 9

In the fourth image, 1200 J of heat flows from a hot reservoir at $$T_H = 650\ \mathrm{K} to a $$cold reservoir at $$T_C = 350\ \mathrm{K}. $$What is the total change in entropy of the universe?

Accepted Answer

$$1.6\ \mathrm{J/K}$$

Question 10

Which of the following best describes a reversible process in thermodynamics?

Accepted Answer

A process that can be reversed so that both the system and environment return to their original states

Question 11

What is the value of the specific heat ratio $$\gamma$$ for a monatomic ideal gas?

Accepted Answer

$$\gamma = \frac{5}{3}$$

Question 12

Which law of thermodynamics states that it is impossible to reach absolute zero temperature?

Accepted Answer

Third Law

Question 13

A heat pump delivers $$Q_H to a $$house using $$W of $$work input. What is the coefficient of performance (COP) for the heat pump?

Accepted Answer

$$COP = \frac{Q_H}{W}$$

Question 14

Which of the following is a correct statement of the First Law of Thermodynamics?

Accepted Answer

$$\Delta U = Q - W$$

Question 15

If a Carnot engine has a hot reservoir at $$T_H = 500\ \mathrm{K}$$ and a cold reservoir at $$T_C = 250\ \mathrm{K}$$, what is its maximum possible efficiency?

Accepted Answer

$$0.50$$

Question 16

Which of the following devices is an example of a reverse heat engine?

Accepted Answer

Refrigerator

Question 17

For a monatomic ideal gas, what is the molar specific heat at constant pressure ($$C_P$$)?

Accepted Answer

$$C_P = \frac{5}{2}R$$

Question 18

Which of the following best describes the Zeroth Law of Thermodynamics?

Accepted Answer

If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

Question 19

If a heat engine has an efficiency of $$e = 0.30$$ and absorbs $$Q_H = 1000\ \mathrm{J}$$ from the hot reservoir, how much work does it perform?

Accepted Answer

$$W = 300\ \mathrm{J}$$

Question 20

Which of the following is NOT a consequence of the Second Law of Thermodynamics?

Accepted Answer

The entropy of an isolated system can decrease.

Thermodynamics: Heat Capacities, Heat Engines, and the Laws of Thermodynamics- lecture 30

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