Energy is a quantifiable state function of every physical system. Energy allows one to predict how much work a physical system could be made to do, or how much heat it can exchange. In general, the presence of energy is detected by an observer or system any time there is a change in the properties of another object or system. This is where the early exploration of the nature of energy began. As our understanding of the nature of energy progressed, scientists found it to exist in many forms not readily observable by the average unaided observer. In fact, in some cases the presence of particular types of energy prevents changes from being easily observed in a particular object or system. Empirical observations have shown that the total quantity of energy is conserved. This makes the concept of energy very important in physics.

Subcategories

E

• Electric power
• Energy development

F

• Fuels

G

• Green vehicles

R

• Renewable energy

U

• Units of energy

Articles in category "Energy"