AP Physics Thermodynamics & Modern Physics

Question 1

What does the first law of thermodynamics state?

Accepted Answer

Energy cannot be created or destroyed, only transformed

Answer

The first law of thermodynamics is a restatement of the principle of conservation of energy. It asserts that energy cannot be created or destroyed within an isolated system. Instead, energy can only be transformed from one form to another, such as from chemical potential energy to kinetic energy or heat.

Question 2

What is entropy?

Accepted Answer

The disorder or randomness of a system

Answer

Entropy is a thermodynamic property that quantifies the degree of disorder or randomness in a system. A higher entropy value indicates a greater number of possible microscopic arrangements for the system's particles, reflecting a more chaotic or less ordered state. It is a measure of the unavailability of a system's thermal energy for conversion into mechanical work.

Question 3

What is the relationship between temperature and kinetic energy?

Accepted Answer

Temperature increases with increasing kinetic energy

Answer

Temperature is a macroscopic measure directly related to the average translational kinetic energy of the particles (atoms or molecules) within a substance. As the particles move faster and possess higher average kinetic energy, the substance's temperature increases. Conversely, lower average kinetic energy corresponds to a lower temperature.

Question 4

What is the purpose of a heat engine?

Accepted Answer

To convert thermal energy into mechanical work

Answer

The primary purpose of a heat engine is to convert thermal energy (heat) into mechanical work. It achieves this by operating between a high-temperature reservoir and a low-temperature reservoir, absorbing heat from the hotter source, converting a portion of it into useful work, and expelling the remaining heat to the colder sink.

Question 5

What is the second law of thermodynamics?

Accepted Answer

Entropy of an isolated system increases over time

Answer

The second law of thermodynamics states that the total entropy of an isolated system can only increase over time, or remain constant in ideal reversible processes. This fundamental law implies that natural processes tend towards states of greater disorder and randomness, and it's why heat spontaneously flows from hot to cold, not the other way around.

AP Practice Test

AP Practice Test

AP Physics Thermodynamics & Modern Physics