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Lecture Eighteen Physics 100 Fall 2012

# Lecture Eighteen Physics 100 Fall 2012

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## Lecture Eighteen Physics 100 Fall 2012

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1. Lecture Eighteen Physics 100 Fall 2012 • Conservation of Energy

2. Announcements • No Lab Tomorrow. • Lab WILL BE HELD Wednesday, Thursday and Tuesday of next week. • Second writing assignment due on 12/12/12 • Exam 3 discussion

3. Electric Motors • An electric motor is a device that converts electrical energy into mechanical energy. • Electric motors use magnetic force to cause motion.

4. A Simple Electric Motor

5. We will investigate electric motors in lab this week.

6. Electric Motors Get “mechanical” energy (motion) out Put “electrical” energy (electricity) in.

7. Electric Generators Put “mechanical” energy in to cause rotation Get “electrical” energy (electricity) out

8. Electric Energy and Power Watt x hour or a kilowatt-hour is a unit of energy which can be converted into a Joule.

9. Electric Power Because V=iR

10. Kinetic (or Mechanical) Energy • Kinetic energy (or mechanical energy) is energy associated with motion. • KE=½ mv2 where m is the mass of an object and v is velocity or speed

11. Electric Generators Put “mechanical” energy in to cause rotation Get “electrical” energy (electricity) out

12. Conservation of Energy • Energy is not created or destroyed. • Rather, energy changes form (electrical to mechanical for example). • Or, is transferred from one object to another.

13. Conservation of Energy • Where did the energy come from to start with?

14. There is only solar energy

15. Some of the Types of Energy • Kinetic (mechanical) • Electrical • Heat • Light from the sun and other objects • Sound • Potential (stored): Chemical bonds including meat and plants, gravitational potential energy, springs, petroleum