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EFFICIENCY. By: Amanda Koon St. Robert’s Catholic High School. The Law of Conservation of Energy. Energy is neither created nor destroyed . It changes from one form to another . We can use energy path diagrams to illustrate energy transformations into both useful and wasted forms.
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EFFICIENCY By: Amanda Koon St. Robert’s Catholic High School
The Law of Conservation of Energy • Energy is neither created nor destroyed. It changes from one form to another. • We can use energy path diagrams to illustrate energy transformations into both useful and wasted forms
Incandescent light Fluorescent light Energy Path Diagrams Visible light 27W heat Visible light 100W heat
Aerodynamic drag 2.6% Mechanical energy engine losses 17.2% Accessories 2.2% Rolling resistance 4.3% 5.7% of energy from fuel available to propel car Drive train losses 5.6% Thermal energy engine losses 62.4% Energy Path Diagram Typical combustion engine to transmission 100%
Efficiency • Definition: • Efficiency is the ratio of useful energy/work/power output to the total energy/work/power input. • Unit Analysis
Example 1Efficiency of a incandescent light What is the efficiency of this light bulb? Visible light 5% Heat 95%
Example 2Efficiency of a Crane What is the efficiency of a crane that uses 5.10 x 105 J of energy to lift 1000 kg a vertical height of 32.0m?
Example 3Lighting efficiency A particular light bulb is known to be 7.5% efficient. • How much light energy would actually be provided by a 100W light bulb in one minute of operation? • What would be the effective light power from this 100W bulb?
Think About This… In general, the greater number of steps in transferring energy, the less efficient the process. Why is this so?