Q: Refer to the P-V diagram for a gas cycle. If the system moves from point A to B at constant pressure of 200 kPa and the volume changes from 0.2 $$m^3 to 0.8$$ $$m^3$$, what is the work done during this segment?

$$W = P \Delta V = 200\ \text{kPa} \times (0.8 - 0.2)\ \text{m}^3 = 120\ \text{kJ}$$

Q: Using the P-V diagram for a gas cycle, calculate the total net work done by the system in one complete cycle.

$$W_{net} = (P_{AB} \times \Delta V_{AB}) - (P_{CD} \times \Delta V_{CD}) = 200\ \text{kPa} \times (0.8 - 0.2)\ \text{m}^3 = 120\ \text{kJ}$$

Question 1

A system receives 100 J of heat. If the thermal energy of the system remains constant, how much work does the system do?

Accepted Answer

100 J

Question 2

Engine 1 takes in 100 J of heat from a hot reservoir and does 20 J of work. Engine 2 takes in the same amount of heat from the hot reservoir and does 25 J of work. Is the efficiency of engine 1 greater than, less than, or equal to the efficiency of engine 2?

Accepted Answer

less than

Question 3

Which of the following equations illustrates the First Law of Thermodynamics?

Accepted Answer

$$\Delta E = Q - W$$

Question 4

In an adiabatic compression of an ideal gas, no heat is exchanged with the surroundings ($$Q = 0). $$What happens to the temperature of the gas?

Accepted Answer

The temperature increases because work is being done on the gas.

Question 5

Find the heat associated with this process: $$W = 50\ J$$, $$\Delta E = 50\ J.$$

Accepted Answer

100 J

Question 6

A runner does $$8.2 	imes 10^6$\ J of $$work and gives off $$3.3 	imes 10^6$\ J of $$heat. Determine $$\Delta E$$ for the runner.

Accepted Answer

$$-1.45 	imes 10^6$\ J$$

Question 7

Which of the following physical quantities is zero in a constant-volume process?

Accepted Answer

$$W = 0$$

Question 8

Which of the following physical quantities is zero in an isothermal process?

Accepted Answer

$$\Delta E = 0$$

Question 9

Which of the following physical quantities is zero in an adiabatic process?

Accepted Answer

$$Q = 0$$

Question 10

A fluid expands by $$0.42\ m^3$ at a pressure of 121$$\ kPa$$. How much work is done by the fluid?

Accepted Answer

19,000 J

Question 11

A gas is contained in a cylinder with a pressure of $$140\ kPa$$ and an initial volume of $$0.66\ m^3$. How much work is done by the gas if it expands at constant pressure to twice the initial volume?

Accepted Answer

67,000 J

Question 12

If you rub your hands together, the entropy of the universe changes. Choose the best explanation for this.

Accepted Answer

The heat produced by the rubbing raises the temperature of the hands and the air, which increases the entropy.

Question 13

A heat engine operates between a hot reservoir at the Kelvin temperature of $$T_h$$ and a cold reservoir temperature of $$T_c. If $$both temperatures are doubled, what happens to the efficiency of the engine?

Accepted Answer

Stays the same

Question 14

What is the efficiency of an engine that takes in 610 J of heat in the process of doing 230 J of work?

Accepted Answer

38%

Question 15

An engine receives 780 J of heat from a hot reservoir and does 110 J of work. What is the heat given off to the cold reservoir?

Accepted Answer

670 J

Question 16

Absolute zero cannot be reached.

Accepted Answer

True

Question 17

No engine can be 100% efficient.

Accepted Answer

True

Question 18

A process that occurs at a constant temperature is called:

Accepted Answer

Isothermal

Question 19

Refer to the P-V diagram for a gas cycle. If the system moves from point A to B at constant pressure of 200 kPa and the volume changes from 0.2 $$m^3 to 0.8$$ $$m^3$$, what is the work done during this segment?

Accepted Answer

$$W = P \Delta V = 200\ 	ext{kPa} 	imes (0.8 - 0.2)\ 	ext{m}^3 = 120\ 	ext{kJ}$$

Question 20

Using the P-V diagram for a gas cycle, calculate the total net work done by the system in one complete cycle.

Accepted Answer

$$W_{net} = (P_{AB} 	imes \Delta V_{AB}) - (P_{CD} 	imes \Delta V_{CD}) = 200\ 	ext{kPa} 	imes (0.8 - 0.2)\ 	ext{m}^3 = 120\ 	ext{kJ}$$

PHYS Ch 11 Quiz – Thermodynamics and Heat Engines Study Guide

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