text: This quantity is represented as the ratio between the linewidths of arrows on Sankey diagrams.
full_question: This quantity is represented as the ratio between the linewidths of arrows on Sankey diagrams. The coefficient of performance is approximately the inverse of this quantity. According to the Shockley- Quiesser limit, a bandgap of 1.4 eV corresponds to a maximum of this quantity for a p-n junction in solar cells. This quantity increases slowly as the compression ratio increases, since it is a function only of that ratio and the adiabatic index for many processes. This quantity will be (*) maximized if the hot and cold reservoirs have infinite and zero temperature respectively, and in a Carnot engine, it equals one minus the ratio of those temperatures. For 10 points, name this quantity symbolized eta, which equals the ratio of net work output over heat input, which would ideally be 100% for a thermodynamic cycle.
first_sentence: This quantity is represented as the ratio between the linewidths of arrows on Sankey diagrams.
raw_answer: thermodynamic efficiency [or eta until it is read]