AP Physics 2 Exam Question:
A 500 g piece of copper is heated from 25°C to 125°C. During the heating process, 1000 J of thermal energy is added to the copper. Assume that the specific heat capacity of copper is 0.386 J/g°C.
Answer:
The change in internal energy (ΔU) can be calculated using the formula:
ΔU = m * c * ΔT
where: m = mass of the copper (500 g) c = specific heat capacity of copper (0.386 J/g°C) ΔT = change in temperature (125°C - 25°C) = 100°C
Plugging in the values:
ΔU = 500 g * 0.386 J/g°C * 100°C ΔU = 19300 J
Therefore, the change in internal energy of the copper is 19300 J.
According to the first law of thermodynamics, the 1000 J of energy could have transferred to the copper through heating (transfer of thermal energy), work done on the copper, or transfer of energy in the form of radiation.
The second law of thermodynamics states that in any energy transfer or conversion, the total entropy of a closed system will always increase over time. When thermal energy is converted into work, some of the energy is always lost as waste heat due to inefficiencies in the conversion process. This waste heat contributes to an increase in the entropy of the system, making it impossible for all of the thermal energy added to the copper to be converted into work.
In summary, the second law of thermodynamics dictates that some energy will always be lost as waste heat, preventing the complete conversion of thermal energy into work.
This question tests your understanding of the first and second laws of thermodynamics, as well as your ability to calculate the change in internal energy and apply the principles to real-world scenarios.