Laws of thermodynamics, heat engines, and entropy concepts for a college physics sequence.
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- What does the First Law of Thermodynamics state?
- Energy cannot be created or destroyed, only converted from one form to another. In a system, the change in internal energy equals heat added minus work done by the system.
- Write the First Law of Thermodynamics as an equation.
- ΔU = Q - W, where ΔU is change in internal energy, Q is heat added to the system, and W is work done by the system.
- Define internal energy in a thermodynamic system.
- The total energy contained within a system due to the random motion of its molecules, excluding macroscopic kinetic and potential energy.
- Define entropy.
- A measure of the disorder or randomness in a system, related to the number of microscopic states a system can occupy at a given macroscopic condition.
- What does the Third Law of Thermodynamics state?
- The entropy of a perfect crystal at absolute zero (0 K) is zero. As temperature approaches absolute zero, entropy approaches a constant minimum.
- State the Zeroth Law of Thermodynamics.
- If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This defines temperature as a fundamental quantity.
- What is absolute zero in Kelvin?
- 0 K, which equals approximately -273.15 degrees Celsius or -459.67 degrees Fahrenheit.
- Define a reversible process in thermodynamics.
- A process where the system remains in equilibrium throughout and can be reversed by infinitesimal changes to external conditions, returning both system and surroundings to initial states.
- Define an irreversible process in thermodynamics.
- A real process where the system is not in equilibrium and cannot be reversed to return both system and surroundings to their initial states.
- What is heat in thermodynamics?
- Energy transfer between a system and its surroundings due to a temperature difference. Heat flows spontaneously from higher to lower temperature.
- What is work in thermodynamics?
- Energy transfer due to a force acting through a distance. In thermodynamics, it typically refers to expansion or compression work done by or on a gas.
- What is an isothermal process?
- A thermodynamic process where temperature remains constant throughout. For an ideal gas, ΔU = 0, so Q = W.
- What is an adiabatic process?
- A thermodynamic process where no heat is exchanged between the system and surroundings (Q = 0). Work done equals the change in internal energy (W = -ΔU).
- What is an isobaric process?
- A thermodynamic process at constant pressure. The work done by the gas is W = P times ΔV.
- What is an isochoric (isovolumetric) process?
- A thermodynamic process at constant volume (ΔV = 0). No work is done by or on the gas (W = 0).