Mr. Rogers' IB Physics Topics |
Key Thermodynamic Terms and Equations
Perfect Gas Law
pV = n RT
1st Law of Thermodynamics - Conservation of energy
ΔUint = Q - W
Adiabatic - no heat transfer, occurs with a rapid expansion or contraction of a gas
W = ΔUint
Isobaric - constant pressure, typical for a pneumatic cylinder
W = P (ΔV)
Isovolumetric - constant volume, can't do work
W = 0
ΔUint = Q
Isothermal (perfect gas) - constant temperature
W = nRT ln(Vi/Vf)
Carnot Cycle - the perfect heat engine
- Isothermal expansion
- Adiabatic expansion
- Isothermal compression
- Adiabatic compression
Heat Engine - converts heat to work. According to the 2nd Law 100% of a quantity of heat can never be converted to work.
Actual efficiency = W/Qh
Carnot efficiency = 1 - Tc/Th
Heat Pump - makes heat flow "backwards" from cold to hot, COP is coefficient of performance, the higher the better
Actual COP = Qc/W
Ideal: COP = Tc/(Th - Tc)