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Science 9

Science 9. Aim: Electrophoresis and Building a circuit. Agenda. Science Sizzler ( A shton, Connor) Electrophoresis and Building a circuit notes Next class. Electrochemistry. The Study of Chemical Reactions involving Electricity. Electrochemistry Applications. Electrolysis

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Science 9

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  1. Science 9 Aim: Electrophoresis and Building a circuit

  2. Agenda • Science Sizzler (Ashton, Connor) • Electrophoresis and Building a circuit notes • Next class

  3. Electrochemistry • The Study of Chemical Reactions involving Electricity

  4. Electrochemistry Applications Electrolysis • Process using electricity to split molecules into their elements. Ex. split water into hydrogen and oxygen gas using electricity Uses include: • making PVC pipe • producing fuel for space shuttle

  5. Electrochemistry Applications Electroplating -coating other materials with metals Example: - Electroplating jewelry with gold or silver GOLD PLATED MACBOOK

  6. C Circuits (what we already know) A A) An Energy Source = Supplies electrons B) A Conductor = Material allowing flow of electrons C) A Load = A device that converts electrical energy to another form of energy (ex. heat or light) D) A Switch (Optional) = Closes and opens a circuit B D

  7. INSULATORS Microscopically Examining… Within the substance’s atom, electrons are tightly bound to the positively charged nucleus… … therefore resist moving between the atoms (i.e. No Potential for Electrical Current)

  8. CONDUCTORS Microscopically Examining… Within the substance’s atom, electrons are NOT tightly bound to the positively charged nucleus… … therefore they are freer to move between atoms & do so when connected to an electrical source

  9. MostCONDUCTORSare not ‘perfect’ Meaning that the atom’s electrons move quite freely when an electrical current is applied, but… … there is some ELECTRICAL RESISTANCE(electron’s opposition to flow)

  10. Superconductors “Perfect Conductors”  Materials that have no resistance to electron flow Examples: - Mercury when temperature lowered - Other substances lowered to close to absolute zero (-273oC)

  11. RESISTORS  A type of conductor useful in electrical devices  Allows electric current to pass, but provides a good amount of resistance Measured in Ohms ()

  12. RESISTORS Substance with More Resistance = More Energy Per Passing Electron The resistor radiates the gained energy to its surrounding as heat or light Think light bulb

  13. THE SWITCH Mechanism used to turn electricity on and off in a circuit ON = two conductors pressed together, allowing current to flow between the two OFF = two conductors are separated, preventing current to flow Usually enclosed in an insulator to prevent shocks and short circuits

  14. ON OR OFF… OR IN BETWEEN Instead of turning it on or off, sometimes we want to gradually change the current flow in a circuit … to do this we use a Rheostat (or Variable Resistor)

  15. Rheostat (or Variable Resistor) • Increase or Decrease the amount of current in a circuit

  16. THE WATER ANALOGY Using the movement of water as an analogy can help us better understand electricity

  17. The Water Analogy – Source Like flowing water, electricity comes from a source In both, the source must be constantly replenished for the current to continue Example: Snow Pack in the Mountains Example: Electrical Generator

  18. The Water Analogy – Current More Water = More Powerful River Current More Electrons = More Powerful Current in the Conductor

  19. The Water Analogy - Voltage When water is pumped up hill, it gains gravitational potential energy and will flow back down Electrical cells, batteries, & generators pump electrons to point with higher electrical potential (voltage)

  20. The Water Analogy - Resistance Like water smashing into rocks, electricity encounters resistance Current decreases as you add resistance, therefore shorter & thicker conducting wires have the least amount of resistance

  21. Controlling the Current Flow! Quietly Read Page 297 – 302  Questions # 1 - 7

  22. German Scientist Georg Simon Ohm proved a mathematical link between VOLTAGE, CURRENT, & RESISTANCE

  23. OHM’S LAW STATES As long as temperature stays the same…  The resistance of a conductor stays constant  The current is directly proportional to voltage being applies (increase voltage = increase current)  If voltage stays the same, but if a stronger resistor is used, current decreases

  24. OHM’S LAW V = Voltage (volts) I = Current (amps) R = Resistance (ohms) V I R

  25. OHM’S LAW Calculating: V = Voltage (volts) V x I R

  26. OHM’S LAW Calculating I = Current (amps) V ÷ I R

  27. OHM’S LAW Calculating R = Resistance (ohms) V ÷ I R

  28. EXAMPLE QUESTIONS: • A 30 V battery creates a current through a 15 resistor. How much current is created? 2) A motor has and internal resistance of 40 . The motor is in a circuit with a current of 4.0 A. What is the voltage? 3) A current of 625 mA runs through a bulb that is connected to 120 V. What is the resistance of the bulb? (HINT: Units need to be in A, V, & )

  29. BUILDING ELECTRICAL CIRCUITS The most economical way to build a circuit is in a simple loop But we don’t want the entire circuit to fail if one component breaks down!

  30. All Circuits Have… A) An Energy Source = Supplies electrons B) A Conductor = Material allowing flow of electrons C) A Load = A device that converts electrical energy to another form of energy (ex. heat or light) D) A Switch (Optional) = Closes and opens a circuit Switch Load (ex. Bulb) Electrical Source Conductor

  31. DRAWING CIRCUITS Schematic Diagrams = are used by engineers, designers, and scientists to map out electrical circuits. They include special universal symbols that show the components and connections clearly…

  32. THE BASIC ELECTRICAL SYMBOLS Page 312

  33. SERIES vs. PARALLEL CIRCUITS

  34. Ever notice… …that when one bulb on a string of lights burns out, the whole string of lights doesn’t work?? You must search for the bad bulb!! 

  35. Why?? Because the current must travel through each load (bulb) in the circuit So when one bulb breaks, the current flow stops… breaking the entire circuit! Example of a Series Circuit

  36. SERIES CIRCUITS • there is only 1 path for the current to flow through • if the pathway is interrupted (broken) the circuit doesn’t work

  37. SERIES CIRCUITS • adding components increases the total resistance, which decreases the current (ie adding one more light bulb makes them all dimmer)

  38. SERIES CIRCUITS • in your house, switches are wired in series with other components (wall plugs, lights) which makes it possible to turn off all the electricity in that circuit

  39. PARALLEL CIRCUITS • provides more than 1 path for the current to flow through

  40. PARALLEL CIRCUITS • a break or interruption in one pathway does not affect the rest of the pathways in the circuit

  41. PARALLEL CIRCUITS • adding new components (with new pathways) does not affect the resistance in any of the other pathways

  42. Using Parallel Circuits in HOUSEHOLD WIRING • We want to be able to control each individual component (load) separately • A switch on each branch controls only controls the device in that branch • 1 switch in series is an importantsafety precaution in case we need to turn off electricity to all them

  43. MICROCIRCUITS (aka microchips) Microscopic circuits are made up of transistors and resistors Can contain more than 1 million components per centimeter!!!

  44. MICROCIRCUITS Switches are not practical for these tiny circuits. So instead, we use Transistors  A small solid material (usually silicon) consisting of 3 layers. Middle layer controls the current

  45. Making Schematic Diagrams!! Draw and label (using the appropriate symbols) 1) A series circuit that includes:  a battery, a switch, 2 lamps, a voltmeter, a fuse, and a conductor 2) A parallel circuit that includes  a battery, a conductor and 3 components: - one with a switch and a lamp - one with a lampand a rheostat - one with resistor and a ammeter Remember: Parallel circuits should have a switch in series!!!

  46. DIRECT vs. ALTERNATING CURRENT

  47. DIRECT vs. ALTERNATING CURRENT DIRECT CURRENT (DC): • Electricity flows only in one direction • Used by many common devices, such as iPods, computers, cell phones, calculators ALTERNATING CURRENT (AC): • Electricity flows back and forth (60 times per second) • The power supplied to our homes is AC

  48. Power companies generate Alternating Current and transmit it with High Voltage Some lines carry a current with 500,000 volts!! But this voltage must be reduced before the current can be used in our homes

  49. TRANSFORMERS Devices used to change the amount of voltage with very little energy loss. Can be “Step-Down” or “Step-Up” Transformers

  50. STEP-DOWN TRANSFORMERS • Reduces Voltage

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