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Chapter 4

Chapter 4. Energy. Work. Work is force applied over a distance. Expressed in units of foot-pounds (ft.lb.) or inch pounds (in.lb.). Power (P). Power is the amount of work done based on a time period such as seconds or minutes. Work. Force x Dist. Power =. =. Time. Time.

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Chapter 4

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  1. Chapter 4 Energy

  2. Work • Work is force applied over a distance. • Expressed in units of foot-pounds (ft.lb.) or inch pounds (in.lb.)

  3. Power (P) • Power is the amount of work done based on a time period such as seconds or minutes. Work Force x Dist. Power = = Time Time

  4. Horsepower (hp) • Horsepower is used for stating mechanical power. 1 hp = 550 ft.lb. / second In this much time This much work

  5. Watt (W) • Watt is the unit of electrical power. • 1 watt of power is when one volt of electrical pressure moves one coulomb of electricity in one second • Note: one coulomb in one second is an amp. P (watts) = E (volts) x I (amps) 746 watts = 1 hp P=IE

  6. Watt’s Law • P = I x E • I = P / E • E = P / I P I E

  7. Ohm’s Law and Watt’s Law

  8. Wattmeter and Watt-Hours • Electrodynamometer movement – electromagnetic movement found in watt meters • Wattmeter – meter that measures instantaneous power. • Watt-hour meter – measures the amount of power used in a period of time. • Kilowatt hour (kWh) – 1000 watt-hours Power Company

  9. Efficiency • The ratio of electrical power out of a system to the electrical power in to a system. • Generally expressed as a percentage. Power Out % Efficiency = x 100 Power In

  10. Energy Efficiency Rating • A rating by the government to show the energy efficiency of electrical appliances. • Larger the percentage the more efficient the unit.

  11. Gears, Pulleys and Power • Law of conservation of energy – energy cannot be created nor destroyed. It can only be converted from one form to another

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