IB HL Physics Thermodynamic Equations 
Equation  Explanation  
1)  DW = pDV  Work ( mechanical energy transfer ): For work to be done by the system, the volume must increase. If the volume decreases, work is being done on the system.  
2)  DQ = DU + W  1st Law of Thermodynamics: This is a mathematical expression of the law of conservation of energy. Of all the principals in all of science, the 1st law of Thermo is the closest absolute truth. We know of no exceptions.  
3) 

Heat Transfer: The transfer of thermal energy as opposed to work which is the transfer of mechanical energy.  
4) 

Internal Energy: Is increased though positive heat transfer or negative work (work done on the system).  
5) 

Work: Negative work would be work done on the system. Negative work results in a decrease in volume.  
6) 

Thermal Efficiency of a Heat Engine: This equation is based on the 1st Law of Thermo and assumes no energy storage in the system.  
7) 

Thermal Efficiency of a Heat Engine: In reality this equation is more likely to be used than equation 6. Work is measured with a dynamometer is measured by knowing the heat of combustion of the heat engine's fuel and its fuel consumption.  
8) 

Carnot Cycle: A theoretical thermodynamic cycle for a perfect heat engine.  
9) 

Carnot Efficiency: The highest possible efficiency a heat engine can achieve assuming no friction. Real heat engines always achieve less than the Carnot efficiency.  
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