Conservation & Dissipation of Energy

Identifying Useful vs. Wasted Energy: To analyze a system, first define the intended purpose. Any energy transfer that does not contribute to this purpose is classified as 'wasted' or 'dissipated.'

Calculating Efficiency: Efficiency is the ratio of useful energy output to the total energy input. It is expressed as a decimal or percentage: $\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}}$.

Reducing Dissipation: Engineers use specific methods to minimize energy loss. Lubrication (e.g., oil or grease) reduces friction between moving parts, while insulation (e.g., fiberglass or foam) reduces the rate of thermal energy transfer to the surroundings.

Terminology Precision: Never use the word 'lost' when describing energy in an exam. Instead, use the term dissipated to show you understand that the energy still exists but has spread out into the surroundings.

Conservation Checks: When solving problems involving energy transfers (like a falling object), always ensure that the sum of the final energy stores plus any dissipated energy equals the initial energy store.

Efficiency Limits: Remember that efficiency can never be greater than $1$ (or $100\%$). If your calculation results in a value over $100\%$, you have likely swapped the input and output values.

Identify the Pathway: Be prepared to name the pathway of dissipation. Common pathways include heating (due to friction), radiation (light or infrared), and mechanical waves (sound).