1. Marti Andreski De La Salle HS

2. Electricity comes from the Greek word “elektron”, (e-) meaning “amber” (amber is petrified tree resin; when rubbed w/cloth, attracts small pieces of leaves or dust)Electricity comes from the Greek word “elektron”, (e-) meaning “amber” (amber is petrified tree resin; when rubbed w/cloth, attracts small pieces of leaves or dust) Electricity means “stream of moving electrons” but really - the e-‘s and transfer their charge to the next e-Electricity means “stream of moving electrons” but really - the e-‘s and transfer their charge to the next e- atomic structure:atomic structure: Background wiggle

3. Classes of Matter a. conductors - charges are free to migrate; ie: metals (because they have “sea” of e-‘s)a. conductors - charges are free to migrate; ie: metals (because they have “sea” of e-‘s) b. insulators - charges are not free to migrate; ie: non-metals; since e- tightly bound to nucleus; and few e-‘s are available for conductionb. insulators - charges are not free to migrate; ie: non-metals; since e- tightly bound to nucleus; and few e-‘s are available for conduction c. semiconductors - poor conductors; conductivity changes with environment (T); ie: Si, Ge, Cc. semiconductors - poor conductors; conductivity changes with environment (T); ie: Si, Ge, C

4. Laws of Electric Action a. Law of Conservation of Electric Charge: “the net amount of electric charge produced by any process is zero”a. Law of Conservation of Electric Charge: “the net amount of electric charge produced by any process is zero”

5. Laws of Electric Action b. Like charges repel; unlike charges attract ea. otherb. Like charges repel; unlike charges attract ea. other

6. Charge The charges we’re talking about are measurableThe charges we’re talking about are measurable Coulomb – the SI unit of electrical chargeCoulomb – the SI unit of electrical charge 1 C = 6.25 x 10 18 electrons or protons1 C = 6.25 x 10 18 electrons or protons 1 e- = 1.60 x 10 -19 C1 e- = 1.60 x 10 -19 C

7. Coulomb’s Law “the magnitude of the force between two charges, a and b, separated by a distance d, is proportional to the magnitude of the charges and inversely proportional to the square of the distance” (q = “charge”)“the magnitude of the force between two charges, a and b, separated by a distance d, is proportional to the magnitude of the charges and inversely proportional to the square of the distance” (q = “charge”) F ~ q a q b so therefore: F = K q a q bF ~ q a q b so therefore: F = K q a q b d 2 d 2 d 2 d 2 K = 9.0 x 10 9 N. m 2 /C 2K = 9.0 x 10 9 N. m 2 /C 2

8. Symbols and Units UnitSymbol Charge (q) coulombC Distancemetersm forceNewtonN

9. Application of Coulomb’s Law Example: two charges are separated by 3.0 cm. Object A has a charge of +6.0  C, while object B has a charge of +3.0  C. What is the force on object A? (text, p. 474)Example: two charges are separated by 3.0 cm. Object A has a charge of +6.0  C, while object B has a charge of +3.0  C. What is the force on object A? (text, p. 474) Sketch of problem:Sketch of problem: AB3cm +6.0  C+3.0  C Given: q A = +6.0  C q B = +3.0  C d AB = 0.030m F B on A = ? Strategy: Use Coulomb’s Law. Do not include signs. The direction of the force depends on the vector diagram. (In this case, it’s the F B acting on A, so it’s to the “left”. AF B on A

10. Types of Electricity STATICCURRENT Defined “electricity at rest” or, better, “net electric charge” “electricity traveling through conductors and made to perform useful work (ie: batteries, outlets) Involves High Voltage at Low Current Low Voltage at High Current Types/Examples Walking across carpet; Lightning AC = alternating current (outlets) DC = direct current (batteries)

11. Types of Electricity

12. van de Graaf Generator http://www.mos.org/sln/toe/VDG_w orks.movhttp://www.mos.org/sln/toe/VDG_w orks.movhttp://www.mos.org/sln/toe/VDG_w orks.movhttp://www.mos.org/sln/toe/VDG_w orks.mov

13. http://www.eskimo. com/~billb/miscon/ele-map.html Comparison of Voltage vs. Current

14. Static Buildup Known to ruin electronic equipmentKnown to ruin electronic equipment Prevention: wear leather shoes; increase humidity above 60%; use antistatic liquid; use ionizer fans; coat shoes with Al; wear special wrist strapsPrevention: wear leather shoes; increase humidity above 60%; use antistatic liquid; use ionizer fans; coat shoes with Al; wear special wrist straps Can even be a source of igniting gasoline vaporsCan even be a source of igniting gasoline vapors

15. 3 Main Sources of Electricity A. FrictionA. Friction B. ChemicalB. Chemical C. GeneratorC. Generator

16. A. Friction Produces static electricity which can be very HIGH VOLTAGE but very LOW CURRENT (“safe” but hurts!) Static charges are positive and negative; term coined by Ben Franklin (1706-1790) who arbitrarily chose glass + and therefore plastic would be - (no plastic at the time)Static charges are positive and negative; term coined by Ben Franklin (1706-1790) who arbitrarily chose glass + and therefore plastic would be - (no plastic at the time) Positive charge - when a glass rod is rubbed with silk, it is said to have a + charge (Since e-‘s are lost by the glass to the silk which is now -‘ly charged)Positive charge - when a glass rod is rubbed with silk, it is said to have a + charge (Since e-‘s are lost by the glass to the silk which is now -‘ly charged) Negative charge - when a rod of rubber or plastic is rubbed with fur or wool, it is said to be -‘ly charged (the rod took the e-‘s from the fur or wool leaving the rod with more e-‘s than protons and the fur or wool with more protons than e-‘s)Negative charge - when a rod of rubber or plastic is rubbed with fur or wool, it is said to be -‘ly charged (the rod took the e-‘s from the fur or wool leaving the rod with more e-‘s than protons and the fur or wool with more protons than e-‘s)

17. Electrostatic Series aka: Triboelectric Sequence [from - to + OR from GAIN e- easily to LOSE e- easily][from - to + OR from GAIN e- easily to LOSE e- easily] saran wrap, hard rubber, Teflon, plastic, Pt, Au, sulfur, rubber balloon, styrofoam, polyethylene, misc. metals; amber, hard wax, Lucite?, cork, wood, cotton, paper, felt, human hair/skin, silk, lead, cat fur, quartz, wool, nylon, mica, glass, (Lucite?) rabbit fursaran wrap, hard rubber, Teflon, plastic, Pt, Au, sulfur, rubber balloon, styrofoam, polyethylene, misc. metals; amber, hard wax, Lucite?, cork, wood, cotton, paper, felt, human hair/skin, silk, lead, cat fur, quartz, wool, nylon, mica, glass, (Lucite?) rabbit fur Why is there more static in winter than in summer?Why is there more static in winter than in summer? H 2 O molecules are polar; attract e-‘s H 2 O molecules are polar; attract e-‘s

18. Demos – Static Electricity DemoObservationExplanation Rubber Rod in stream of water Rubber rod, fur, water Butterfly and styrofoam Butterfly and rubbed styrofoam Styrofoam Balls – each with same charge Styrofoam Balls – one rubbed with fur

19. B. Chemical when 2 different elements come together, one will always have a greater ability to give up e-‘s than the other. (see St’d Reduction Potentials table)when 2 different elements come together, one will always have a greater ability to give up e-‘s than the other. (see St’d Reduction Potentials table) That can be used to get charges flowing from one element to another (that is what electricity is all about)That can be used to get charges flowing from one element to another (that is what electricity is all about) This is how it works…This is how it works…

20. The Zn-Cu Cell Zn in a sol’n of ZnSO 4Zn in a sol’n of ZnSO 4 (this is the ANODE since OXIDATION, the LOSS OF ELECTRONS, occurs)(this is the ANODE since OXIDATION, the LOSS OF ELECTRONS, occurs) Cu in a sol’n of CuSO 4 (this is the CATHODE since REDUCTION, the GAIN OF ELECTRONS, occurs)Cu in a sol’n of CuSO 4 (this is the CATHODE since REDUCTION, the GAIN OF ELECTRONS, occurs) Salt Bridge – allows ions to transfer back & forth, completing the circuitSalt Bridge – allows ions to transfer back & forth, completing the circuit Wire & Meter – electric charge goes thru & is measuredWire & Meter – electric charge goes thru & is measured Zn loses 2e- to the solution Zn +2 2e - Cu +2

21. Animation http://www.chem.iastate.edu/group/Greenbowe/sections /projectfolder/animations/CuZncell.html

22. What happens? Zn wears away (oxidizes or rusts) while Cu builds upZn wears away (oxidizes or rusts) while Cu builds up stronger batteries (higher Voltage) are made with substances that are FARTHER away from each other on the chart since there is GREATER POTENTIAL DIFFERENCE (think of the roller coaster hill being higher!)stronger batteries (higher Voltage) are made with substances that are FARTHER away from each other on the chart since there is GREATER POTENTIAL DIFFERENCE (think of the roller coaster hill being higher!) DEMO 2: Zn/Mn Sample Battery:DEMO 2: Zn/Mn Sample Battery: Zn casing (anode)Zn casing (anode) Cardboard wrapCardboard wrap Mn pasteMn paste Carbon rod; button (cathode)Carbon rod; button (cathode)

23. SRP : 25 o C and 1.0M aqueous Li + + e-  Li(s) -3.05 Cs + + e-  Cs(s) -2.92 K + + e-  K(s) -2.92 Rb + + e-  Rb(s) -2.92 Ba 2+ + 2 e-  Ba(s) -2.90 Sr 2+ +2 e-  Sr(s) -2.89 Ca 2+ + 2 e-  Ca(s) -2.87 Na + + e-  Na(s) -2.71 Mg 2+ + 2 e-  Mg(s) -2.37 Be 2+ + 2 e-  Be(s) -1.70 Al 3+ + 3 e-  Al(s) -1.66 Mn 2+ + 2 e-  Mn(s) -1.18 Zn 2+ + 2 e-  Zn(s) -0.76 Cr 3+ + 3 e-  Cr(s) -0.74 Fe 2+ + 2 e-  Fe(s) -0.44 Cr 3+ + e-  Cr 2+ -0.41 Cd 2+ + 2 e-  Cd(s) -0.40 Tl + + e-  Tl(s) -0.34 Co 2+ + 2 e-  Co(s) -0.28 Ni 2+ + 2 e-  Ni(s) -0.25 Sn 2+ + 2e-  Sn(s) -0.14 Pb 2+ + 2 e-  Pb(s) -0.13 2 H + + 2 e-  H 2 (g) 0.00 S(s) + 2 H + + 2 e-  H 2 S (g) 0.14 Sn 4+ + 2 e-  Sn 2+ 0.15 Cu 2+ + e-  Cu+ 0.15 Cu 2+ + 2 e-  Cu(s) 0.34 Cu + + e-  Cu(s) 0.52 I 2 (s) + 2 e-  2 I - 0.53 Fe 3+ + e-  Fe 2+ 0.77 Hg 2 2+ + 2 e-  2 Hg(l) 0.79 Ag + + e-  Ag(s) 0.80 Hg 2+ + 2 e-  Hg(l) 0.85 2 Hg 2+ + 2 e-  Hg 2 2+ 0.92 Br 2 (l) + 2 e  2 Br - 1.07 O 2 (g) + 4 H + + 4 e-  2 H 2 O(l) 1.23 Cl 2 (g) + 2 e-  2 Cl - 1.36 Au 3+ + 3 e-  Au(s) 1.50 Co 3+ + e-  Co 2+ 1.82 F 2 (g) + 2 e-  2 F - 2.87

25. More easily oxidized (Give up e- easier) More easily reduced (Take up e- easier)

26. Using the SRP Chart to Determine Cell Voltage The pair combined is Zn and Cu There are 3 locations for Cu; which is used? We have to know the reaction. Cu +2 ions are coming out of solution and becoming Cu metal, so… Cu +2 + 2e-  Cu Since Zn is higher on the table, it is the oxidized half; Cu is reduced. NOTE: is the form Zn +2 + 2e-  Zn written as an oxidation? (LOSS OF e- = oxidation!)

27. C. Generator This will be discussed in detail in the Electromagnetism unitThis will be discussed in detail in the Electromagnetism unit Basically, since electricity is a flow of electric charge and any time electrons can flow that’s electricity, electrons can be made to flow in a wire that is put in a magnetic field and turned. If there are a lot of turnings of wire and continuous movement of the magnet, e- keep flowing and electricity is generated.Basically, since electricity is a flow of electric charge and any time electrons can flow that’s electricity, electrons can be made to flow in a wire that is put in a magnetic field and turned. If there are a lot of turnings of wire and continuous movement of the magnet, e- keep flowing and electricity is generated.