1. Coulomb’s Law

2. Answer Me!!!  An inflated balloon which has been rubbed against a person’s hair is touched to a neutral wall and remains attracted to it. Draw a diagram that best represents the charge distribution on the balloon and the wall. Wall

3. Law of Conservation of Charge  When charged objects are put in contact with one another, the charge of each object is equal to the total charge divided by the number of objects.

4. Practice Problem 1  Two identical metal spheres, A and B, are on insulated stands. Sphere A has a net charge of -4x10 -6 C, Sphere B has a net charge of -6x10 -6 C. If the spheres are brought into contact and then separated, What will the charge on sphere A be?

5. Practice Problem 2  When a neutral metal sphere is charged by contact with a positively charged glass rod, the sphere Loses electrons Gains electrons Loses protons Gains protons

6. Coulomb’s Law  Electrostatic Force is the force of attraction (or repulsion) between opposite (or same) charges.  Fe – electrostatic Force  k – electrostatic constant: 8.99 x 10 9 Nm 2 /C 2  q – charge of particle  r – distance between centers

7. Practice Problem 3  What is the approximate electrostatic force between two protons separated by a distance of 1.0 x 10 -6 m?

8. Final Thought…  Two protons, A and B, are located a distance of 1 m apart. Draw arrows to indicate the gravitational force F G and the electrostatic force F e between A and B. Then calculate the net force on A. AB