1. Electricity Intro

2. Lightning

3. Properties of Charge

4. Elementary Electrostatics Rubbing a balloon on a wool jumper makes the balloon attract your hair The balloon is said to be “charged” or to have an “electric charge” Similarly glass rubbed with silk/fur will become “charged” Charged glass will attract a charged balloon Two charged balloons will repel each other

5. Experiments Show…. Benjamin Franklin (1706-1790) –Two types of charge Charles Coulomb (1736-1806) –Coulomb’s Law Robert Milikan (1868-1953) –Quantisation (1909)

6. Properties of Charge: Two types of charge Arbitrarily named –Positive (+ve) e.g. glass –Negative (-ve) e.g. wax & rubber

7. Like Charges Repel … +ve -ve

8. & Opposites Attract… +ve-ve+ve-ve

9. Properties of Charge: Charge is Quantised Whenever we measure the amount of charge we get a value that is an integer multiple of a unique number e q = N e Charge Integer Fixed number

10. Properties of Charge: Charge is always conserved –Charge is never created or destroyed –The process of “charging” is really “moving” charge from one place to another

11. Quiz Why does your hair stand on end in a lightning storm?

12. Quiz 2 A: more than before rubbing? B: the same as before? C: less than before? Rub a balloon on your hair, the balloon attracts your hair. Is the total amount of charge in the balloon and in your hair...

13. Equipment and methods of Charging

14. The Electroscope Used to detect and crudely measure charge

15. Earthing The Earth is a practically limitless supply (or sink) of charge

16. Van de Graf Generator

17. Different Methods for Charging Friction –e.g. rubbing a balloon with wool Conduction –e.g. touching an electroscope Induction –e.g. balloon sticking to a wall

18. Charging by Friction

19. Charging by Conduction

20. Induction Balloon on wall Wall is neutral and an insulator +ve Charges move slightly towards balloon -ve Charges move slightly away from balloon Wall is still neutral but surface has small residual charge, sufficient to hold baloon

21. Charging an Electroscope by Induction

22. Induction to Charge Object

23. Quiz A: the water moves away from the rod B: the water doesn’t move C: the water moves towards the rod If a positively charged rod is brought near a trickle of water the water moves towards it. What happens if we use a negatively charged rod?

24. Quiz a: A is positive b: A is negative c: A is neutral d: not enough information Object A attracts object B. If we know that B is positively charged what can we say about A?

25. Experiments and applications of Static Electricity The electrostatic Precipitator Photocopies and Laser Printers Electostatic painting

26. Summary: Lecture 1 Equipment and Techniques –Electroscope “Measures charge” –Earthing Earth as a limitless supply or sink of charge –Van de Graaff Generator “Generates charge” Introduced the concept of charge Properties of charge Two types +ve & -ve Like repel Opposites attract Charge always conserved Charge quantised Methods of charging Friction Conduction Induction

27. Homework Read Section 11.1 Pg 471 #2 – 9