Conservation of Energy

This lesson covers the principle of conservation of energy, energy transfer diagrams and the concept of dissipation, as required by the Edexcel GCSE Combined Science specification (1SC0). This is one of the most important ideas in all of physics.

---

The Principle of Conservation of Energy

Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed.

This means:

• The total energy in a closed system is always the same before and after any change.
• Energy is never lost — it is always transferred somewhere.
• When we say energy is "wasted", we mean it has been transferred to a store that is not useful (usually the thermal store of the surroundings).

Exam Tip: You must be able to state the conservation of energy principle in your own words. A good version is: "The total energy of an isolated system remains constant; energy is transferred between stores but the total stays the same."

---

Closed Systems

A closed system is one where no energy (or matter) can enter or leave. In a closed system, the total energy is constant.