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Power tells us how fast work is done!

Learn about the concepts of power, work, and wasted energy in physics. Explore how power is measured in watts (W) and work in joules (J). Discover the relationship between power and efficiency, and calculate the power efficiency of a drum fan and wind turbine blade designs.

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Power tells us how fast work is done!

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  1. Power tells us how fast work is done!

  2. Power is measured in Watts (W) Work is measured in Joules (J) ⇒remember work = ΔPE or ΔKE Time is measured in seconds (s) One watt is the same as one joule per second.

  3. Why did Power quit his job? • He didn’t want to work overtime.

  4. for understanding! • If two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds. • Which student does the most work? Explain. • They do the same amount of work. They apply the same force to lift the same barbell the same distance over their heads. • Which student delivers the most power? Explain. • Ben is the most “power-full” since he does the same work in less time.

  5. Wasted Energy • Wasted energy is anything that keeps ALL of the kinetic energy (work) from being turned into electrical energy. • For example, a solar cell that is 20% efficient will lose 80% of the energy it produces! • Turn to the person next to you and identify a way in which electrical energy can be wasted.

  6. Main Sources of Wasted Energy • Friction or resistance • Heat lost to surroundings

  7. Calculating Efficiencies

  8. This is very much like a heat engine!!! • Heat engine: heat in heat out (waste) work done • Power efficiencies: power in power out (waste) work done

  9. Power Efficiency Lab Purpose: The purpose of this lab is to test and calculate the power efficiency of a drum fan and then your wind turbine blade designs.

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