Electricity and magnetism

1. Electricity and magnetism

2. Nobel prize: graphene Andre Geim University of Manchester Konstantin Novoselov

3. The unit of electric current is the: • Volt • Amp • Coulomb • Ohm • Watt

4. Did you read the assignment>? • Yes • No

5. A superconductor is a material that: • Has lots of electrons • Insulates your home • Has zero resistance • Nobody has created yet • Has extremely high voltage

6. Heat engines  electricity

8. The basics of electrostatics

10. Two equal mass balls are charged, and hang on strings as shown: What can we conclude about the signs of Q1 and Q2? A: One is "+", the other is "-" B: Both are "+" C: Both are "-" D: Both must be the same charge (but we can't tell if they're both "+", or both "-")

11. Two uncharged conducting spheres, A and B, are suspended from insulating threads so that they touch each other. While a negatively charged rod is held near, but not touching sphere A, the two spheres are separated. How will the spheres be charged, if at all? Sphere A Sphere B A) 0 + B) - + C) 0 0 D) - 0 E) + - B A

12. An electron traveling horizontally enters a region where a uniform electric field is directed upward. What is the direction of the force exerted on the electron once it has entered the field? A) to the left B) to the right C) upward D) downward E) out of the screen

13. Pick up here Oct 14

14. If we put bunch of electrons in a box, they will A) clump together. B) spread out uniformly across box. C) make a layer on walls. D) do something else.

15. Voltage? Voltage is the energy per charge.

16. CRT: Cathode ray tube (tv)

17. Current Amount of charge I = = time Current is the flow of electric charges.

18. Why isn’t this bird toast? • The bird understands quantum physics • The wire has no current running through it • The bird’s other leg isn’t touching the ground • Wires are insulated for safety – people walk up to wires and touch them too with no problem

19. Resistance

20. IA IB • Which current is bigger? • IA • IB • They are the same

21. R R is big resistance r is small resistance IB r IA • Which current is bigger? • IA • IB • They are the same

22. Tues Oct 19 pick up here

23. Opinions about circuit stuff Are the conceptual circuit sims (PhE`T) that we’ve been playing with helpful? • Yes • No • Sort of…

24. Opinions about circuit stuff What about the ones I’ve drawn on the board — helpful? • Yes • No • Sort of…

25. Opinions about circuit stuff Are our exercises helping you to see how electricity ‘works’ in our lives? • Yes • No • Sort of…

26. Opinions about circuit stuff Would more math help you to see what’s happening? • Yes • No • Not sure

27. Opinions about circuit stuff How well do you understand voltage, current, and resistance? • I can build a computer from scratch now • I can explain all of the examples that we’ve been through • I have a grasp on most of the concepts • I might struggle if you asked me a question like “which lightbulb is brighter” in a circuit with 2 or 3 bulbs and a battery • I’m actually kind of lost

28. Opinions about circuit stuff How much longer do you want to spend on this stuff? • I want more time to explore and discuss with other students • I want more instruction • I want to move on to new stuff

29. Worksheet on circuits for next week’s hw? • Yes please • No! • Just make it optional

30. Other feedback?

31. Resistance

32. Table of resistivities

35. Surface mount devices

36. Review… IA IB V • Which current is bigger? • IA • IB • They are the same

37. Review… r R V • Which voltage drop is bigger? • Across r • Across R • They are the same

38. R R is big resistance r is small resistance IB r V IA • Which voltage drop is bigger? • Across r • Across R • They are the same

39. R R V

40. R R #2 V R R #1 • Which circuit has brighter light bulbs? • #1 • #2 • All light bulbs are the same brightness V

41. R R R V V #2 #1 • Which circuit has brighter light bulbs? • #1 • #2 • All light bulbs are the same brightness

43. Capacitor