Energy

Energy is a fundamental quantity that every physical system possesses. Energy of physical system in a certain given state is defined as the amount of work W needed to change the state of the system from some initial state (called reference state or reference level) to the given state.

Energy use

Main articles: energy development, energy policy

Related Topics:
Energy development - Energy policy

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The way in which humans use energy is one of the defining characteristics of an economy. The progression from animal power to steam power, then the internal combustion engine and electricity, are key elements in the development of modern civilization. Future energy development, for example of renewable energy, may be key to avoiding the effects of global warming.

Related Topics:
Steam power - Internal combustion engine - Electricity - Future energy development - Renewable energy - Effects of global warming

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