Bellwork What particle does the moving in electricity? The electron Calendar Today Coulombs 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 Coulombs Law H.W. due Coulombs Law 2/28/13 Grounding The Earth is a enormous source or well of electrons (i.e. can give or take in a lot of electrons) Coulombs Law Coulombs Law: The relationship between electric force, charges and distance. Charge Unit A coulomb (C) is the unit for charge Static Electricity C Lightning Bolts C Inverse Square Law (recap) Inverse Square Law: A physical quantity that is inversely proportional to the square of the distance from quantity. Inverse Square Law: Inverse Square Law Plot Inverse Square Law: Gravitational Force Electric Field Electric Force EM waves Light Sound Coulombs 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 ) Coulombs 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 Metric Prefixes Revisited Common Prefixes M (mega-) k (kilo-) c (centi-) m (milli-) (micro-) n (nano-) 1 M (unit) = 10 6 units 1 k (unit) = 10 3 units 1 c (unit) = units 1 m (unit) = units 1 (unit) = units 1 n (unit) = units Common Prefixes M (mega-) k (kilo-) c (centi-) m (milli-) (micro-) n (nano-) 1 M (unit) = 10 6 units 1 k (unit) = 10 3 units 1 c (unit) = units 1 m (unit) = units 1 (unit) = units 1 n (unit) = units New Prefix Formula Card Coulombs Law: Example: Determine the electrical force of attraction between two pith balls with separate charges of +8.5 C and -7.9 C when separated a distance of 0.25 m.