3.  We learned about charge and got a conceptual feel for what it is.  We identified charge with the fundamental building clocks of atoms.  We studies charge transfer from a number of perspectives.  We looked at polarization of insulating materials  We learned about conductors and what actually moves.  We learned how to make someone’s hair stand on end.  We learned about how to stick a balloon to a wall.  We learned how to understand these effects. should  At least you should have learned these things.

4. An aluminum nail has an excess charge of +3.2 µ C. How many electrons must be added to the nail to make it electrically neutral? A) 2.0 × 10 13 B) 2.0 × 10 19 C) 3.2 × 10 16 D) 3.2 × 10 6 E) 5.0 × 10 – 14 e=1.60217646 × 10 -19 coulombs

5. F is a VECTOR and is positive if the two charges repel and negative if they attract. How do F 21 and F 12 compare?

6. Unit Charge etc. Then add ‘em up as vectors

7. Three point charges have equal magnitudes, two being positive and one negative. These charges are fixed to the corners of an equilateral triangle, as the drawing shows. The magnitude of each of the charges is 5.0  C, and the lengths of the sides of the triangle are 3.0 cm. Calculate the magnitude and direction of the Electric Field on charge C. (diagram)

9. And then there was Gauss

10. How much flux leaves the sphere?? q

12. Gauss’s Law Gaussian Surface

13. Two spherical shells have a common center. +q charge is spread uniformly over the inner shell, which has a radius of 0.050 m. A + 8q charge is added to the outer shell, which has a radius of 0.15 m. Find the magnitude and direction of the electric field at the following distances (measured from the common center). (a) 0.20 m (b) 0.10 m (c) 0.025 m

14. Potential Energy q