2. Gauss’s Law The total flux of electric field out of any closed surface is equal to the charge contained inside the surface divided by.

3. Conductors and insulators Charges reside at the surface of the conductor Conductor E=0 + ++ + + + + + + + + + + + +

4. Solid conducting sphere with charge Q A E r V r A

5. Electric field of a ball of charge Q Electric field outside of a charged sphere is exactly the same as the electric field produced by a point charge, located at the center of the sphere, with charge equal to the total charge on the sphere.

6. Ionization and corona discharge There is maximum potential to which a conductor in air can be raised because of ionization. Small potentials applied to sharp points in air produce sufficiently high fields just outside the point to ionize the surrounding air.

7. The metal mast at the top of the Empire State Building acts as a lightning rod. It is struck by lightning as many as 500 times each year. A lightning rod has a sharp end so that lightning bolts will pass through a conducting path in the air that leads to the rod; a conducting wire leads from the lightning rod to the ground.

8. Benjamin Franklin

9. "For my own part I wish the Bald Eagle had not been chosen the Representative of our Country. He is a Bird of bad moral Character. He does not get his Living honestly. You may have seen him perched on some dead Tree near the River, where, too lazy to fish for himself, he watches the Labour of the Fishing Hawk; and when that diligent Bird has at length taken a Fish, and is bearing it to his Nest for the Support of his Mate and young Ones, the Bald Eagle pursues him and takes it from him. "With all this Injustice, he is never in good Case but like those among Men who live by Sharping & Robbing he is generally poor and often very lousy. Besides he is a rank Coward: The little King Bird not bigger than a Sparrow attacks him boldly and drives him out of the District. He is therefore by no means a proper Emblem for the brave and honest Cincinnati of America who have driven all the King birds from our Country.... "I am on this account not displeased that the Figure is not known as a Bald Eagle, but looks more like a Turkey. For the Truth the Turkey is in Comparison a much more respectable Bird, and withal a true original Native of America... He is besides, though a little vain & silly, a Bird of Courage, and would not hesitate to attack a Grenadier of the British Guards who should presume to invade his Farm Yard with a red Coat on." --Benjamin Franklin, in a letter to his daughter

10. First exam Tuesday, Feb 16, 7 pm 105-109 Heldenfels Sections 521, 522 room 105 Sections 523, 525 room 107 Section 527 room 109

11. No calculators and cell phones BRING YOUR STUDENT ID!

12. What is included? Chapters 1-4

14. Have a great day! Hw: All Chapters 4-5 problems and exercises Reading: Chapter 5