91影视

Energy is defined as the 鈥渁bility or capacity to do work, which is the ability to exert a force causing displacement of an object.鈥�

It can be in the form of potential energy, kinetic energy, thermal energy, electrical energy, chemical energy, nuclear energy, or any other form.

The major difference between a closed and an open system (in terms of energy) is that in a closed system, the total energy cannot change (there is no inflow or outflow of energy), whereas it can in an open system.

$$\begin{gathered} {\mathrm{螖贰}}_{\mathrm{open}\mathrm{system}}鈮�0 \\ {\mathrm{螖贰}}_{\mathrm{closedsystem}}=0 \end{gathered}$$

• Open systems: An automobile, a person, and the Earth are all open systems. Through its exhaust, a car exchanges energy with its environment (among others). A human exchanges energy with the environment by eating and heat (for example, to maintain a consistent body temperature). Because the Earth gets heat from the Sun and then radiates it into space, its overall energy fluctuates.
• Closed systems:An insulated picnic trunk and the Universe are both closed systems. Because no heat can be transported from or to the picnic chest if it is completely insulated, it is a closed system. Nothing can change the overall energy of the Universe because there are no systems outside of it.

Therefore, an automobile, a person, and the Earth are all open systems in terms of energy. An insulated picnic chest and the Universe are both closed systems in terms of energy.