1. Bellwork What particle does the moving in electricity? The electron

2. Calendar Today – Coulomb’s Law Friday (2/14):  Start Introductory Lab on Circuits  Electric Fields and Electric PE H.W. due Monday (2/17)  Finish the lab in-class  Coulomb’s Law H.W. due

3. Coulomb’s Law 2/28/13

8. Grounding The Earth is a enormous source or well of electrons (i.e. can give or take in a lot of electrons)

9. Coulomb’s Law Coulomb’s Law: The relationship between electric force, charges and distance.

10. Charge Unit A coulomb (C) is the unit for charge Static Electricity 0.0000001 C Lightning Bolts 15-350 C

11. Inverse Square Law (recap) Inverse Square Law: A physical quantity that is inversely proportional to the square of the distance from quantity.

12. Inverse Square Law:

13. Inverse Square Law Plot

14. Inverse Square Law: Gravitational Force Electric Field Electric Force EM waves Light Sound

15. Coulomb’s Law and Universal Law of Gravity Simularities Both action at a distance forces Both inverse squares of force and distance Both have quantities that cause a force ( charge for electrical & mass for gravity )

16. Coulomb’s Law and Universal Law of Gravity Differences Both have constants… but the electrical force is much, much stonger then the gravitional force (10 20 times stronger) Gravity is only attractive where electricity is attractive and repulsive

17. Metric Prefixes Revisited

18. Common Prefixes M (mega-) k (kilo-) c (centi-) m (milli-) μ (micro-) n (nano-) 1 M (unit) = 10 6 units 1 k (unit) = 10 3 units 1 c (unit) = 10 -2 units 1 m (unit) = 10 -3 units 1 μ (unit) = 10 -6 units 1 n (unit) = 10 -9 units

19. Common Prefixes M (mega-) k (kilo-) c (centi-) m (milli-) μ (micro-) n (nano-) 1 M (unit) = 10 6 units 1 k (unit) = 10 3 units 1 c (unit) = 10 -2 units 1 m (unit) = 10 -3 units 1 μ (unit) = 10 -6 units 1 n (unit) = 10 -9 units New Prefix

20. Formula Card Coulombs Law:

21. Example: Determine the electrical force of attraction between two pith balls with separate charges of +8.5 μC and -7.9 μC when separated a distance of 0.25 m.