2-4.P34左邊2.3段

This is scientific law tells us that when one form of energy is converted to another form in any physical or chemical change,energy input always equals energy output.

這是科學的定律告訴我們 當能源的一種形式被轉換到任何的物理或化學變化的另一種形式的時候，能源輸入總是等於能源輸出。

No matter how hard we try or how clever we are, we cannot get more energy out of a system than we put in.

不管我們如何努力嘗試，不管我們多聰明，我們不能得到比　我們輸入　更多的系統能源輸出。

This is one of nature's basic rules.

這是自然的基本規則之一。

Because the first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another, you may be tempted to think there will always be enough energy.

因為熱力學的第一定律說，能源不能夠被創造或者被破壞，只從一種形式轉換到另一種，你可能被誘惑認為，總是有足夠的能源。


Yet if you fill a car's tank with gasoline and drive around or use a flashlight battery until it is dead, something has been lost.

然而如果你將一個汽車油箱裝滿汽油且開車繞周圍　或　使用一個手電筒電池直到它沒電，有些事物已經失去。

But whats is it?

但是什麼是它？

The answer is energy quality, the amount of energy available that can perform useful work.

答案是能源的質量，可得到的能源多寡能夠執行有用工作。