Chapter Seven

Section 1 Section 2 Section 3 Section 4 Section 5

Section 6 Section 7 Section 8 Formulas

Heating

Any flow of thermal energy from a higher to a lower temperature is called heating.

Temperature is a quantitative measure of warmth as measured by a thermometer.

The Law of Heating: Thermal energy flows spontaneously from higher to lower temperature, but not from lower to higher temperature.

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Heat Engines: Using Thermal Energy to Do Work A heat engine is any cyclic device that

uses thermal energy to do work. Its energy efficiency, the fraction of its input thermal energy that is converted to work, will be higher if the input temperature is higher and the exhaust temperature is lower.

A heat engine’s ejected thermal energy is called exhaust.

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Energy Quality: Things Run Down

Thermal energy is considered to be of lower quality than other energy forms, because of the second law’s restrictions on converting it to other forms.

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The Law of Entropy: Why You Can’t Break Even

Entropy is the measure of microscopic disorganization, the disorganization on a microscopic scale.

The Second Law of Thermodynamics: The total entropy of all the participants in any physical process cannot decrease during that process, but it can increase.

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The Automobile

Internal combustion engines burn a fuel-air mixture. The high combustion temperature gives it a high pressure, so that hot gases can push strongly on a piston, a movable metal plate connected to a rod. Diagram

External combustion occurs in a fuel that then provides thermal energy to a second substance that does the actual work

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Diagram

Transportation Efficiency

Transportation efficiency is useful output, such as distance traveled, passengers moved or freight moved, per unit of fuel input.

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The Steam-Electric Power Plant

A steam turbine is a large rotating device that turns when it feels a higher pressure on the front side than on the back.

The turbine turns an electric generator that creates electricity when the turbine causes it to rotate. Diagram

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Diagram

Resource Use and Exponential Growth

A non-renewable is a resource that cannot be readily replaced within a human lifetime.

Renewable resources, such as wood or solar energy, can be sustained indefinitely, assuming they are consumed at less than the replacement rate.

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Formulas

ThermE (input) -> Work + Therm E (exhaust)

Energy Efficiency = work outputthermal energy input

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