Thermodynamics Flashcards
What is a black body radiator?
- A perfect emitter and absorber of all possible wavelengths of light.
- The distribution of the intensity of these wavelengths depends on temperature, such that the higher the temperature is, the higher frequency the highest intensity wavelength is.
What is the Stephan-Boltzmann law?
Of a black body radiator:
Total power output L = σAT⁴
How do you derive the equation for modular kinetic theory of gasses?
- Define a cube of side length l with a particle inside of mass m and velocity v
- Do force = change in momentum (2mv) over time, with the time being that between the particle hitting one wall, and the particle hitting the same wall again (2l/v)
- Do pressure = F/A
- Collect ls into volume so V = l³
- Divide by the three directions
- Take the mean square of the velocities
What is Wien’s law?
λmax T = 2.898x10^-3
Why does temperature not increase when a liquid boils?
- KE stays constant
- Energy goes to potential energy of particles causing them to move further apart (producing gas) / energy goes to potential energy of particles which breaks intermolecular bonds
What is internal energy?
The energy of a substance due to the random distribution of kinetic and potential energy of its molecules.
What are the 5 assumptions for an ideal gas?
- No intermolecular forces.
- Collision time is negligible.
- Motion is random and collisions are elastic.
- Motion follows Newton’s Laws.
- Particles move in straight lines.
What is the ideal gas law?
PV = NkT
What do you always get wrong when asked to find the root mean square speed using the modular kinetic theory equations?
root mean square speed / √<c²> !!!!
not just <c²>
What should you always do when working out heat transfer equations?
Always write the full equation, and make sure all changes of state and temperature are accounted for.
