| |
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) |
| +DQ |
= |
thermal energy transferred into the
system |
|
Heat Transfer: The transfer of
thermal energy as opposed to work which is the transfer of mechanical
energy. |
|
4) |
| +DU
|
= |
increase in internal energy of the system |
|
Internal Energy: Is
increased though positive heat transfer or negative work (work done on the
system). |
| 5) |
| +DW |
= |
work done by the system |
|
Work: Negative work would be work
done on the system. Negative work results in a decrease in volume. |
|
6) |
|
Thermal Efficiency:
The % of heat input into a heat engine which is output as work.
This equation is based on the 1st Law of Thermo and assumes no energy
storage in the system.
Wikipedia Article |
| 7) |
|
Thermal Efficiency: While not
specifically given in the IB Data Book, in reality
this equation is more likely to be used than equation 6 because Qc
can be hard to measure. Both equations 6 and 7 are identical
in meaning. 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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