AP Physics Physics: Thermodynamics & Modern Physics 2

Question 1

A Carnot engine operates between a hot reservoir at 600 K and a cold reservoir at 300 K. What is its maximum theoretical efficiency?

Accepted Answer

50%

Answer

Carnot efficiency = 1 - T_cold/T_hot = 1 - 300/600 = 0.50, or 50%.

Question 2

Which thermodynamic process occurs at constant pressure?

Accepted Answer

Isobaric

Answer

An isobaric process occurs at constant pressure, allowing volume and temperature to change.

Question 3

In the photoelectric effect, increasing the intensity of light while keeping frequency constant will:

Accepted Answer

Increase the number of ejected electrons per second

Answer

Higher intensity means more photons per second, so more electrons are ejected, but each photon still delivers the same energy.

Question 4

What does the area under a P-V diagram curve represent?

Accepted Answer

Work done by or on the gas

Answer

The area under a P-V curve equals the work done by the gas during the process W = ∫P dV.

Question 5

An electron transitions from the n=3 to n=1 energy level in a hydrogen atom. This transition produces:

Accepted Answer

An emitted photon in the ultraviolet range

Answer

The n=3 to n=1 transition in hydrogen is part of the Lyman series, which produces ultraviolet photons.

AP Practice Test