Heat, Work, and Efficiency

• The increase in temperature can be achieved by raising T or by decreasing Tc by the same ΔT.
• Kelvin–Planck Form of the Second Law states that it is impossible to construct a heat engine that, operating in a cycle, produces no effect other than the input of energy by heat from a reservoir and the performance of an equal amount of work.
• Clausius Statement of the Second Law states that it is impossible to construct a cyclical machine whose sole effect is to transfer energy continuously by heat from one object to another object at a higher temperature without the input of energy by work.
• Clausius and Kelvin–Planck Statements include Clausius statement: It is impossible to construct a cyclical machine whose sole effect is to transfer energy continuously by heat from one object to another object at a higher temperature without the input of energy by work.
• Kelvin–Planck statement: It is impossible to construct a heat engine that, operating in a cycle, produces no effect other than the input of energy by heat from a reservoir and the performance of an equal amount of work.
• A certain refrigerator has a COP of 5.00.
• Three engines operate between reservoirs separated in temperature by 300 K.
• When the refrigerator is running, its power input is 500 W.
• The cold reservoir’s temperature is that of the outside air, approximately 300 K.
• The cost of heating a home can vary depending on the type of heating system used.
• The maximum thermal efficiency of a steam engine can be increased by increasing the temperature of the boiler.
• A steam engine has a boiler that operates at 500 K.
• The energy from the burning fuel changes water to steam, and this steam then drives a piston.
• A sample of water of mass 500 g and temperature 20.0°C is placed in the freezer compartment.
• The Carnot engine operates between the hottest reservoir and the coldest reservoir, and its efficiency is determined by the Carnot cycle, which can be represented as a PV diagram.
• The energy entering an electric heater by electrical transmission can be converted to internal energy with an efficiency of 100%.
• The thermal efficiency of a Carnot cycle is calculated as the area of the curve enclosing the cycle, divided by the area of the curve enclosing the reversible process.
• The reservoir temperatures are as follows: Engine A: T = 1 000 K, Tc = 700 K; Engine B: T = 5 800 K, Tc = 500 K; Engine C: T = 5 600 K, Tc = 300 K.
• No real heat engine operating between two energy reservoirs can be more efficient than a Carnot engine operating between the same two reservoirs, according to Sadi Carnot.
• An electric heat pump with a COP of 4.00 can replace an electric heating system, resulting in a different cost of heating a home.
• The efficiency of a Carnot engine is determined by the Carnot cycle, which can be represented as a PV diagram.