Physics: Thermodynamics & Modern Physics Flashcards
7 cards from real AP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physics: Thermodynamics & Modern Physics flashcards as text
A Carnot engine operates between a hot reservoir at 600 K and a cold reservoir at 300 K. What is its maximum theoretical efficiency?
Answer: 50%
Carnot efficiency = 1 - T_cold/T_hot = 1 - 300/600 = 0.50, or 50%.
Which thermodynamic process occurs at constant pressure?
Answer: Isobaric
An isobaric process occurs at constant pressure, allowing volume and temperature to change.
In the photoelectric effect, increasing the intensity of light while keeping frequency constant will:
Answer: Increase the number of ejected electrons per second
Higher intensity means more photons per second, so more electrons are ejected, but each photon still delivers the same energy.
What does the area under a P-V diagram curve represent?
Answer: Work done by or on the gas
The area under a P-V curve equals the work done by the gas during the process W = ∫P dV.
An electron transitions from the n=3 to n=1 energy level in a hydrogen atom. This transition produces:
Answer: An emitted photon in the ultraviolet range
The n=3 to n=1 transition in hydrogen is part of the Lyman series, which produces ultraviolet photons.
A radioactive isotope has a half-life of 10 years. What fraction of the original sample remains after 30 years?
Answer: 1/8
After 3 half-lives (30 years), the fraction remaining is (1/2)^3 = 1/8.
Which statement best describes the Second Law of Thermodynamics?
Answer: The entropy of an isolated system tends to increase over time
The Second Law states that the total entropy of an isolated system cannot decrease over time; natural processes increase entropy.