AP Physics 2 Quiz: First Law of Thermodynamics with Answers

📚 Quick Study Guide

• 🔥 The First Law of Thermodynamics states that the change in internal energy ($\Delta U$) of a system equals the net heat transfer ($Q$) into the system minus the net work ($W$) done *by* the system: $\Delta U = Q - W$.
• 🌡️ Internal energy ($U$) is the sum of all the kinetic and potential energies of the molecules in a system. For an ideal gas, internal energy is directly proportional to temperature.
• ⚙️ Work ($W$) done by a gas is $W = \int P dV$, where $P$ is pressure and $V$ is volume. For constant pressure, $W = P\Delta V$.
• ☀️ Heat ($Q$) is the transfer of energy due to temperature differences. Heat added to a system is positive, while heat removed is negative.
• 🧊 Adiabatic process: No heat transfer ($Q = 0$), so $\Delta U = -W$.
• ♨️ Isothermal process: Constant temperature ($\Delta T = 0$), so $\Delta U = 0$, and $Q = W$.
• ⚖️ Isobaric process: Constant pressure. Work done is simply $P\Delta V$.
• 🔒 Isochoric process: Constant volume ($\Delta V = 0$), so $W = 0$, and $\Delta U = Q$.

🧪 Practice Quiz

1. A system absorbs 500 J of heat and performs 200 J of work. What is the change in internal energy of the system?
   1. A. 200 J
   2. B. 300 J
   3. C. 500 J
   4. D. 700 J
2. In an adiabatic process, which of the following is true?
   1. A. The temperature remains constant.
   2. B. The pressure remains constant.
   3. C. No heat is transferred.
   4. D. No work is done.
3. During an isothermal expansion of an ideal gas, what happens to the internal energy of the gas?
   1. A. Increases
   2. B. Decreases
   3. C. Remains constant
   4. D. First increases, then decreases
4. A gas expands from a volume of 1 m³ to 3 m³ at a constant pressure of 2 Pa. How much work is done by the gas?
   1. A. 2 J
   2. B. 4 J
   3. C. 6 J
   4. D. 8 J
5. Which of the following processes occurs at constant volume?
   1. A. Isobaric
   2. B. Isothermal
   3. C. Adiabatic
   4. D. Isochoric
6. If the internal energy of a system decreases by 300 J while 100 J of work is done *on* the system, how much heat is transferred?
   1. A. 200 J absorbed
   2. B. 200 J released
   3. C. 400 J absorbed
   4. D. 400 J released
7. For an ideal gas undergoing an isobaric process, if the temperature doubles, what happens to the volume?
   1. A. Halves
   2. B. Doubles
   3. C. Remains constant
   4. D. Quadruples