1 / 7

Power & Efficiency

Energy & Transformations. Power & Efficiency. Power. Power: The rate of doing work or transferring energy. Measured in Watts (W) 1 W = 1 J / s (joule per second) It is given by: Watts are commonly used to measure the power used by electrical appliances. Where: P=power (W)

mauve
Download Presentation

Power & Efficiency

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Energy & Transformations Power & Efficiency

  2. Power • Power:The rate of doing work or transferring energy. • Measured in Watts (W) • 1 W = 1 J / s (joule per second) • It is given by: • Watts are commonly used to measure the power used by electrical appliances. • Where: • P=power (W) • W = work (J) • ∆E = Energy transferred (J) • ∆t= time interval (s)

  3. Example 1 • A runner transforms 3.5 x 105 J of energy running in the New York City Marathon. If it takes 3.25h to run, what is the runner’s power? Express in Watts & Kilowatts

  4. Example #2 • A 45kg student climbs a flight of stairs 4m high in 25 seconds. Determine • The potential energy of the student at the top of the stairs. • The student’s power.

  5. Efficiency • Efficiency: The ratio of the useful energy output of a device to the required input energy. • Typically expressed as a percentage (%). • It is given by:

  6. Example #3 • An incandescent light bulb requires 1500 J of electrical energy to produce 150 J of light energy. • Write the energy transformation equation. • Calculate the efficiency of the light bulb. • Draw the energy flow diagram.

  7. Example #4 • A 125 W ceiling fan produces 4500 J of wind energy in 48 seconds. Determine: • The power output of the ceiling fan • The efficiency of the ceiling fan • The energy flow diagram

More Related