Exam 11: Using Energy

An ideal Carnot engine extracts 529 J of heat from a high-temperature reservoir during each cycle, and rejects $225 \mathrm {~J}$ of heat to a low-temperature reservoir during the same cycle. What is the efficiency of the engine?

A heat engine receives 7000 J of heat and loses 3000 J in each cycle. What is the efficiency of this engine?

A fixed amount of an ideal monatomic gas is maintained at constant volume as it is cooled by 50 K. This feat is accomplished by removing 400 J of energy from the gas. How much work is done by the gas during this process?

A Carnot engine operates between two reservoirs with unknown temperatures. If the Carnot engine operates at $67 \%$ efficiency, what is the ratio of the absolute temperatures of the reservoirs, T_c/T_h?

A heat pump absorbs heat from the atmosphere at a rate of 30 kW. If work is being done to run this heat pump at a rate of 7.7 kW, what is the coefficient of performance (COP) of the heat pump?

For a certain ideal Carnot engine, the hot reservoir is 35 C° higher than the cold reservoir. If this engine is to have an efficiency of 20%, what must be the temperature of the hot reservoir?