2. Lecture 3 Chapter 3 - Electrical Properties Chapter 4 - Electrical Quantities

3. b b Making Molecules with Atoms b b http://www.youtube.com/watch?v=qmgE0 w6E6ZI http://www.youtube.com/watch?v=qmgE0 w6E6ZI b b ok

4. Elements and Compounds b Element - a substance that cannot be reduced to a simpler substance by chemical means b ie: iron, gold, silver...

5. Atoms b The smallest particle of an element that retains the characteristics of that element. b Atoms are like letters, molecules are like words b ie: the water molecule

6. Electrons vs. Protons b Electrons are negatively charged (-) b Protons are positively charged (+) b Electrons and protons attract each other

7. Atomic Number b Atomic Number is the number of protons in its nucleus

8. Electron orbits b Electrons can only “jump” orbits or shells in steps The number of electrons in any particular orbit follows the equation: # Electrons = 2n 2 n = orbit number

9. Electron Orbits b There can be as many as 7 shells in an atom –K, L, M, N, O, P, and Q b How many electrons, if full, would be in 7th shell? b How many shells would the electrons in the silver atom fill?

10. Sub-shells of Orbits –Each Orbit (K, L, M, N, O, P, and Q) has sub-shells (s, p, d, f, g) http://en.wikipedia.org/wiki/Electron_shell –How many electrons in Orbit N sub-shell f? 14

11. Orbit 1 Orbit 2 Orbit 3 Orbit 4 Orbit 5...... Subshell 1 Subshell 2 Subshell 3 Subshell 4 Subshell 5

12. Valence Electrons b The valence electron is the number of electrons in the outermost sub-shell of an atom. b Valence electrons may be easy or hard to be freed. Atoms tend to want to be neutral.

13. How many valence electrons in silver? 1

14. 1

15. How many valence electrons in gold? 1

16. How many valence electrons in aluminum? 3

17. Conductors vs. Insulators b Conductors usually have 3 or less valence electrons. Why? b Insulators usually have 5 or more valence electrons. b Semiconductors? How many valence electronsHow many valence electrons DefinitionDefinition b Best Conductors: SilverSilver CopperCopper GoldGold AluminumAluminum b Good Insulators RubberRubber PlasticPlastic GlassGlass b Common semiconductors GermaniumGermanium SiliconSilicon

18. Resistive Constants

19. Static Electricity b Shielding wire b EMI (ElectroMagetic Interference) b Grounding

20. Ionization b Positive vs Negative ions

21. Random Video of the Day

22. B * C R2R2R2R2 A A = 2 B = 3 C = 4 R = 2 F = F = ?

23. Coulomb’s Law of Charges b Relational Force between particles F = force in Newtons q1, q2 = the charges in coulomb units k e = constant = 8.988x10 9 r = distance in meters between charges = ? =.4mC 56nC = 5mm 1 Coulomb is like a large group of electrons 6.25x10^18 electrons r - Can also be imagined as the area in the electric field Answer 8053 N So how many Coulomb’s is 1 electron???1.6 x 10 -19 C

24. More Coulomb’s Law practice problems...(aka worksheet)

25. Chapter 4 – Electrical Properties b What is Current? b What is Voltage? b What is Resistance?

26. Kinetic vs Potential Energy b Kinetic Energy b Potential Energy The energy possessed by a body because of its motion The energy of a particle or system of particles derived from position, or condition, rather than motion. ie: a roller coaster, a moving car ie: a stretched rubber band, a coiled spring. In our case, a BATTERY!

27. Introduction Video

28. Current b Current is a movement of charged particles b Within metal conductors, the charged particles that are moving are electrons. b These electrons flow when there is a potential difference in the charges across a conductor. Aka: protons are on the other side.

29. Current – electron flow model b The current you are used to working with is nothing more than moving electrons, moving from a region of negative charge to an area of positive charge. b As a potential difference is impressed across the conductor, the positive terminal of the battery attracts electrons beyond point A. Point A becomes positive because it now has an electron deficiency. As a result, electrons are attracted from point B … and so on. b This is true for metal conductors.

30. Current – Conventional current flow b If you Google “current” or look in a friends electrical engineering book, you might find that current flows from positive to negative. b A few perspectives on this include: Currents of positive ionsCurrents of positive ions Hole Charge Current in p-type semiconductorsHole Charge Current in p-type semiconductors b Arrows shown on diodes and transistors are for current, not electron flow

31. Electron Flow vs. Conventional Current Flow b Which one do we use??? Electron FlowElectron Flow b However I will still call it current. b However I will still call it current. +-+- +-+- Electron FlowConventional Current Flow

32. Current Magnitude b If the potential difference is increased, the electric field is stronger, the amount of energy imparted to a valence electron is greater, and the magnitude of current is increased.

33. Current Magnitude b If 6.25 x 10 18 electrons pass a given point in one second, then this is called one amp. electrons second 6.25 x 10 18 Coulomb second = 1 = 1 Amp Q t I =

34. Voltage b So what causes there to be a potential difference in charges across a conductor? (how do you get protons to be stored on one side and electrons on the other?)(how do you get protons to be stored on one side and electrons on the other?) b There are 6 ways this can be done, and this is part of your homework to look up.

35. Voltage b Voltage is also known as Electromotive Force (EMF)Electromotive Force (EMF) –Usually associated with the voltage a battery makes Potential differencePotential difference –Difference in charges

36. Voltage Example b How much voltage is produced when you shock someone? When you feel it:2,000 VWhen you feel it:2,000 V When you see it:8,000 VWhen you see it:8,000 V Maximum spark:25,000 VMaximum spark:25,000 V

37. Other Voltage Examples b AA, AAA, C, D batteries:1.5 V b Car Battery:12V b Cell Phone Battery:3.7 V – 4 V b Watch Battery:3V b Your Computer?:5V

38. Voltage in a battery b Just like a rubber band that has been stretched, there is potential for it to do work when released. b This is similar to the storage of voltage in a battery b Batteries only have a certain amount of charge stored before they run out.

39. Voltage is Relative b Clapping example b Without a reference point, a voltage of 12V is meaningless. b The reference point for voltage most of the time is ground, or 0V. b However, there are different types of grounds. How is an airplane grounded?

40. Voltage is Relative (cont.) b For example, what is the voltage at this point, if each battery is 1.5V? b Depends, if its referenced to: GroundGround Negative side of same batteryNegative side of same battery Top of battery above…Top of battery above… + -

41. Resistance b Resistance is an opposition to current flow b Resistance can be made by: Varying the type of material, (think valence electrons)Varying the type of material, (think valence electrons) Varying the length of materialVarying the length of material Varying the amount or cross-section of materialVarying the amount or cross-section of material b Resistors are like poor conductors. The are somewhere between a conductor and an insulator

42. Resistors (cont.) b b Resistors are a little like transducers in that they convert electrical energy into heat. b b Voltage is converted into heat when electrons bump into each other so voltage is lost.

43. What is the opposite of resistance? b Conductance G = 1R1R Measured in Siemens [S]

44. Voltage, current & resistance analogy - - - - - - - - - - - -

45. A practical Electric Circuit Below is a schematic diagram of a flashlight.

46. Schematic Symbols (pg 59 of book)

47. LAB