Conservation of Energy and Dissipation

In this lesson you will learn about the principle of conservation of energy, what energy dissipation is, and how to reduce unwanted energy transfers. This is a key part of AQA GCSE Combined Science Trilogy (8464), Section 6.1.

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The Principle of Conservation of Energy

Energy cannot be created or destroyed — it can only be transferred from one store to another.

This is one of the most important principles in physics. It applies to every process, in every system, without exception.

In a closed system (one where no energy or matter enters or leaves), the total energy remains constant. Energy may transfer between stores, but the total is always the same.

Example: A Swinging Pendulum

graph LR
    A["GPE store\n(top of swing)"] -->|"Mechanically"| B["KE store\n(bottom of swing)"]
    B -->|"Mechanically"| A
    B -->|"By heating (friction/air resistance)"| C["Internal store\n(surroundings)"]
    style C fill:#ffcccc,stroke:#cc0000

At the top of the swing: maximum GPE, zero KE. At the bottom: maximum KE, minimum GPE. Some energy is dissipated with each swing, so the pendulum gradually swings lower.

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Energy Dissipation