Elementary Charge The charge q of one electron

Elementary Charge • The charge (q) of one electron is q = -1. 60 x 10 -19 coulomb - • The charge (q) of one proton is q = +1. 60 x 10 -19 C +

Coulomb’s Law - • q is the charge • d is the distance from center to center • ke is called the Coulomb constant ke = 8. 99 x 109 N. m 2/C 2 + • F is attractive if the charges are opposite • F is repulsive if the charges are like

Mathematical Relationships q 1 q 2 d 1 1 1 2 1 4 1 1 2 1 1 1 1 2 10 ½ (q 1 q 2) d 2 (1*1)/12 = 1/1 F (2*1)/12 = 2/1 2 1

Mathematical Relationships q 1 q 2 d F 1 (q 1 q 2) d 2 (1*1)/12 = 1/1 1 1 2 1 4 1 1 2 1 1 1 1 2 10 1/2 (2*1)/12 = 2/1 (4*1)/12 = 4/1 (1*1)/22 = 1/22 (1*1)/102 = 1/102 1/(1/2)2 = 1/(¼) 2 2 4 ¼ 1/100 4 1

Why does k have such strange units? ke = 8. 99 x N = 9 10 N. m 2 C 2 m 2 . 2 2 N m /C C 2

Who figured out the value of k?

Coulomb’s Law • Charles Coulomb measured the magnitudes of electric forces between two small charged spheres • He found the force depended on the charges and the distance between them

Force Calculations • If I put two protons, 1 x 10 -3 meter apart what would happen? • What are the forces acting on them? + +

Compare! • What is the electric force between 2 protons 1 x 10 -3 meter apart? • Charge: 1. 6 x 10 -19 C • ke = 9. 0 x 109 N. m 2/C 2 • What is the gravitational force between 2 protons 1 x 10 -3 meter apart? • Mass: 1. 7 x 10 -27 kg • G = 6. 7 x 10 -11 N. m 2/s 2

Force Calculations • What is the electric force between the same two particles? Felectric = 2. 3 x 10 -22 N • What is the force gravity between two protons one meter apart? Fgravity = 1. 9 x 10 -58 N Ratio = 1. 4 x 1039 The electric force is over 1039 times stronger than the force of gravity!

Gravity verse Electricity http: //en. wikipedia. org/wiki/Names_of_large_numbers 1, 400, 000, 000, 000, 000 Thousand x million

Coulomb’s Law Newton’s Law 6 words or less, accurate and connected to science Venn Diagram Competition • A+ = 2 unique contribution • C = 1 unique contribution • D- = 0 unique, but you tried • F- - = you sorta tried, but really were more focused on texting and checking how many friends you have on Facebook.

Homework: Research the INVERSE SQUARE LAW Write a 1 page report on the ISL Report should include • Text • Graph • picture/diagram • 3 examples of concepts that obey the ISL • 1 text resource • 1 video resource • APA formatted references