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Chapter 5

Chapter 5. Sources of Electricity. Objectives. List the six basic sources of electricity. Explain the chemical action that creates electricity in various types of cells. Define polarization. Explain the differences between primary cells and secondary cells. Objectives.

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Chapter 5

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  1. Chapter 5 Sources of Electricity

  2. Objectives • List the six basic sources of electricity. • Explain the chemical action that creates electricity in various types of cells. • Define polarization. • Explain the differences between primary cells and secondary cells. Permission granted to reproduce for educational use only.

  3. Objectives • Distinguish between series and parallel connections in batteries. • Calculate the outputs of batteries connected in series and parallel. • Demonstrate proper use of a hydrometer and explain its use. • Calculate the theoretical capacity of a battery. Permission granted to reproduce for educational use only.

  4. Chemical Action • Sources of voltage • Battery • Electric or voltaic cell • Electricity can be produced by chemical action Permission granted to reproduce for educational use only.

  5. Constructing Voltaic Cells • Blotting paper soaked in salt solution • Wet paper placed between a penny and a nickel Permission granted to reproduce for educational use only.

  6. Constructing Voltaic Cells (Cont.) • Grapefruit with two cuts in the skin • Place a penny and a nickel in the cuts Permission granted to reproduce for educational use only.

  7. Constructing Voltaic Cells (Cont.) • Carbon rod • Strip of zinc • Glass jar of acid and water solution Permission granted to reproduce for educational use only.

  8. Constructing Voltaic Cells (Cont.) • Sulfuric acid and water solution combine to form an electrolyte • Current flows until zinc is consumed • Zinc-carbon cell cannot be recharged Permission granted to reproduce for educational use only.

  9. Types of Primary Cells • Zinc-carbon • Alkaline • Mercury • Lithium • Silver oxide Permission granted to reproduce for educational use only.

  10. Defects in Primary Cells • Polarization • Formation of gas causes cell to be polarized • Depolarizing agents keep the cell producing voltage • Local action • Amalgamation increases life of primary cells Permission granted to reproduce for educational use only.

  11. Zinc-Carbon Cells • Dry cell • Flashlight batteries • Depolarization causes water to form • Cells expand because of water Permission granted to reproduce for educational use only.

  12. Alkaline Cells • Manganese dioxide—positive activator • Zinc powder—negative activator • Caustic alkali—electrolyte • Cylindrical batteries are in wide use (Panasonic Battery Sales Division) Permission granted to reproduce for educational use only.

  13. Mercury Cells • Zinc and mercuric oxide • Create five times more current than other dry cells • Voltage lasts longer • Used in field instruments and portable communications systems Permission granted to reproduce for educational use only.

  14. Lithium Cells • Lithium has highest negative potential • Production of high voltage and lightweight batteries • Intercalation produced through reaction of carbon powder and fluorine gas (Panasonic Battery Sales Division) Permission granted to reproduce for educational use only.

  15. Silver Oxide Cells • Highest electrical volume • Used in watches • Wide range of operating temperatures (Panasonic Battery Sales Division) Permission granted to reproduce for educational use only.

  16. Secondary Cells • Alternating current rectified to direct current to charge batteries • Types • Lead acid cell • Nickel-cadmium cell • Nickel metal hydride cell Permission granted to reproduce for educational use only.

  17. Lead Acid Cells • Lead peroxide and spongy lead • Sulfuric acid and water • Specific gravity measured by hydrometer (ESB Brands, Inc.) Permission granted to reproduce for educational use only.

  18. Nickel-Cadmium Cells • Paste for electrolyte, instead of liquid • Alkaline aqueous solution • Low internal resistance, high discharge current (Panasonic Battery Sales Division) Permission granted to reproduce for educational use only.

  19. Nickel Metal Hydride Cells • Rechargeable battery similar to NiCad battery • Nickel for positive cathode and hydrogen-absorbing alloy for negative anode • Environmentally friendly • Should never be completely discharged Permission granted to reproduce for educational use only.

  20. Batteries in Series • Eout = Eone cell× N • N = number of cells • Positive end of one cell connected to negative end of another Permission granted to reproduce for educational use only.

  21. Batteries in Parallel • Positive ends of cells connected together, negative ends connected together • Voltage stays the same • Battery life extended Permission granted to reproduce for educational use only.

  22. Series-Parallel Connection • Same voltage from each group of cells • Increased capacity by combining groups • Current is added Permission granted to reproduce for educational use only.

  23. Battery Capacity • Measured in ampere-hours (Ah) • Rate of discharge must be considered • Determining factors • Number of plates in each cell • Type of separators • Condition of battery Permission granted to reproduce for educational use only.

  24. Material Safety Data Sheets • Provide information about how to safely handle hazardous materials • Required by law • Information such as proper handling, storage, and disposal • To be used by emergency response personnel, medical personnel, and workers who come in contact with chemicals Permission granted to reproduce for educational use only.

  25. Review What is the voltaic cell? An electric cell Permission granted to reproduce for educational use only.

  26. Review What is a cell in which the chemical action cannot be reversed? Primary cell Permission granted to reproduce for educational use only.

  27. Review What type of cell is an alkaline cell? Primary cell Permission granted to reproduce for educational use only.

  28. Review What is something inserted between or among existing elements? Intercalation Permission granted to reproduce for educational use only.

  29. Review What are some examples of secondary cells? Lead acid, nickel-cadmium, and nickel metal hydride Permission granted to reproduce for educational use only.

  30. Review What is a battery? Two or more cells connected together, enclosed in one case Permission granted to reproduce for educational use only.

  31. Review In what kind of connection are the positive terminals of cells connected together? Parallel connection Permission granted to reproduce for educational use only.

  32. Review What is the capacity of a battery? Its ability to produce a current over a certain period of time Permission granted to reproduce for educational use only.

  33. Other Sources of Electrical Energy • Light • Heat • Mechanical pressure • Magnetohydrodynamic power • Magnetism Permission granted to reproduce for educational use only.

  34. Energy from Light • Photovoltaic cell • Used to create solar arrays Permission granted to reproduce for educational use only.

  35. Photoelectric Control • Photoresistive cells • Similar to a variable resistor • Increases resistance with no light • Decreases resistance for light Permission granted to reproduce for educational use only.

  36. Electrical Energy from Heat • Thermocouple • Thermopile • Galvanometer • Pyrometer Permission granted to reproduce for educational use only.

  37. Electrical Energy from Mechanical Pressure • Mechanical force applied to crystals • Causes a voltage to develop • Piezoelectric effect Permission granted to reproduce for educational use only.

  38. Fuel Cells • Two metallic electrodes • Ionization from gases and electrolyte Permission granted to reproduce for educational use only.

  39. Magnetohydrodynamic (MHD) Power Generation • Conductive plates • Anode • Cathode • Inexpensive type of energy Permission granted to reproduce for educational use only.

  40. Electricity from Magnetism • Dynamo or generator • Magnetism can turn mechanical energy into electrical energy Permission granted to reproduce for educational use only.

  41. Sound Navigation Ranging (Sonar) • Types of sonar • Passive • Active • Similar to radar • Transducers transmit sound waves • A crystal and high-frequency voltage produce vibration • Also used for sonograms Permission granted to reproduce for educational use only.

  42. Review How is a photovoltaic cell constructed? Two thin layers of crystalline silicon, each injected with impurities to form a negative and a positive semiconductor material Permission granted to reproduce for educational use only.

  43. Review What is a light sensitive resistor? Photoresistive cell Permission granted to reproduce for educational use only.

  44. Review How does a thermocouple work? When two dissimilar metals in contact with each other are heated, a potential difference develops between the metals Permission granted to reproduce for educational use only.

  45. Review What is a galvanometer used for? To measure very small currents Permission granted to reproduce for educational use only.

  46. Review What is the term used to describe creating electricity by the mechanical distortion of a crystal? Piezoelectric effect Permission granted to reproduce for educational use only.

  47. Review What are the two conductive plates in an MHD converter called? Anode and cathode Permission granted to reproduce for educational use only.

  48. For Discussion • How can electricity from light be used to solve some of our energy problems? What are the restrictions? • Why do materials such as quartz have a piezoelectric effect? Permission granted to reproduce for educational use only.

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