EFFICIENCY

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# EFFICIENCY - PowerPoint PPT Presentation

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?