A refrigerator has a coefficient of performance of $2.25$, runs on an input of $135$ W of electrical power, and keeps its inside compartment at $5$°C. If you put a dozen $1.0$-L plastic bottles of water at $31$°C into this refrigerator, how long will it take for them to be cooled down to $5$°C? (Ignore any heat that leaves the plastic.)

The coefficient of performance $K=H/P$ is a dimensionless quantity. Its value is independent of the units used for $H$ and $P$, as long as the same units, such as watts, are used for both quantities. However, it is common practice to express $H$ in Btu/h and $P$ in watts. When these mixed units are used, the ratio $H/P$ is called the energy efficiency ratio ($EER$). If a room air conditioner has $K=3.0$, what is its $EER$?

A Carnot engine is operated between two heat reservoirs at temperatures of $520$ K and $300$ K. What is the thermal efficiency of the engine?

A Carnot engine is operated between two heat reservoirs at temperatures of $520$ K and $300$ K. How much mechanical work is performed by the engine during each cycle?

A Carnot engine is operated between two heat reservoirs at temperatures of $520$ K and $300$ K. If the engine receives $6.45$ kJ of heat energy from the reservoir at $520$ K in each cycle, how many joules per cycle does it discard to the reservoir at $300$ K?

Calculate the theoretical efficiency for an Otto-cycle engine with $g=1.40$ and $r=9.50$.

The Otto-cycle engine in a Mercedes-Benz SLK230 has a compression ratio of $8.8$. What is the ideal efficiency of the engine? Use $g=1.40$.