FREE Physics Thermodynamics Questions and Answers
What does the First Law of Thermodynamics state?
The First Law of Thermodynamics is a restatement of the conservation of energy, applied to thermodynamic systems. It says the change in internal energy (ΔU) of a system equals the heat (Q) added to the system minus the work (W) done by the system: ΔU=Q−W.
A gas absorbs 500 J of heat and does 200 J of work. What is the change in its internal energy?
Using the First Law of Thermodynamics (ΔU=Q−W): ΔU=500J−200J=300J.
Which of the following processes describes heat transfer through direct contact?
Conduction occurs when heat is transferred directly through a material or between materials in physical contact, as a result of collisions between molecules or free electrons.
If the temperature of an ideal gas doubles (in Kelvin scale) while the pressure remains constant, what happens to its volume?
For an ideal gas at constant pressure, the relationship between temperature and volume is given by Charles's Law: V 1/T 1 = T /2 If 𝑇2=2𝑇1, then 𝑉2=2𝑉1 .
What is the efficiency of a heat engine that absorbs 500 J of heat from a high-temperature source and rejects 300 J to a low-temperature sink?
The efficiency of a heat engine is given by: Efficiency= Heat Input/Work Output ×100. Efficiency= 200/500×100=40%.