Introducing Electricity


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Introducing Electricity

  1. 1. Introducing Electricity Textbook pg 52
  2. 2. Today’s objectives <ul><li>At the end of this lesson, you will be able to: </li></ul><ul><ul><li>State the appliances that used electricity </li></ul></ul><ul><ul><li>State the sources of electricity </li></ul></ul><ul><ul><li>Define what is electric current and circuit </li></ul></ul><ul><ul><li>Understand the parts of electric circuit </li></ul></ul>
  3. 3. Think-Pair-Share <ul><li>Look at the diagrams below: </li></ul><ul><li>What are needed for these appliances to operate? </li></ul><ul><li>Could you think of similar appliances used for the same purpose in olden days? </li></ul>You got 2 minutes to share with someone beside/ behind you
  4. 4. Electrical Appliances <ul><li>All require electricity to work </li></ul><ul><li>Vacuum cleaner (electricity to kinetic energy) </li></ul><ul><li>Lamp (electricity to light energy) </li></ul><ul><li>Fan (electricity to kinetic energy) </li></ul>
  5. 5. Electrical Appliances <ul><li>Now we cannot live without electricity. </li></ul><ul><li>So many appliances and items we used require electricity </li></ul>
  6. 6. What are the sources of electricity? <ul><li>Main electricity </li></ul><ul><li>Electric cells </li></ul><ul><li>So what’s the difference? </li></ul>
  7. 7. Main Electricity <ul><li>Generated by power stations </li></ul><ul><li>Delivered to homes and industries through wires </li></ul><ul><li>Finally connected to main sockets </li></ul><ul><li>Supplies a lot of electrical energy </li></ul><ul><li>Electric shock </li></ul>
  8. 8. Electric Cells <ul><li>Used in many portable electrical devices </li></ul><ul><li>Supplies small amount of energy </li></ul><ul><li>Safe to touch </li></ul>
  9. 9. Electric Current and Circuit? <ul><li>The rate of flow of electric charges is called electric current </li></ul><ul><li>Electric circuit is the path which the electric current takes </li></ul>
  10. 10. Short video clip Electric circuits - overview
  11. 11. Parts of a Circuit <ul><li>Called electrical components </li></ul><ul><li>Examples </li></ul><ul><ul><li>Connecting wires </li></ul></ul><ul><ul><li>Bulb </li></ul></ul><ul><ul><li>Switch </li></ul></ul><ul><ul><li>Electric cell </li></ul></ul>
  12. 12. Connecting wires <ul><li>Made of two types of materials </li></ul><ul><li>Electrical conductor and electrical insulator </li></ul>Electrical conductor – made of metal such as copper Electrical insulator – made of plastic
  13. 13. Connecting wires <ul><li>Symbols of connecting wires </li></ul><ul><li>Connecting wires (joined) and connecting wires (not joined) </li></ul><ul><li>See pg 56 </li></ul>Joined Not joined
  14. 14. Bulb <ul><li>Symbol of bulb </li></ul>
  15. 15. Switch <ul><li>Symbol of switch </li></ul>Close switch Open switch
  16. 16. Electric Cell <ul><li>Symbol of electric cell </li></ul>One electric cell Two electric cell More than two electric cell
  17. 17. Review Questions <ul><li>What are the two sources of electricity? </li></ul><ul><ul><li>Electric cells and main electricity </li></ul></ul><ul><li>The rate of flow of electric charges is called an ______________ </li></ul><ul><li>The path which the electric current takes is called the _____________ </li></ul><ul><li>What are the 4 parts of circuit we have covered today? </li></ul><ul><ul><li>Connecting wire </li></ul></ul><ul><ul><li>Bulb </li></ul></ul><ul><ul><li>Switch </li></ul></ul><ul><ul><li>Electric cell </li></ul></ul>electric current electric circuit
  18. 18. Match the following: joined connecting wires bulb closed switch one electric cell
  19. 19. Summary <ul><li>What we have learnt today? </li></ul><ul><ul><li>Uses of electricity in our daily life </li></ul></ul><ul><ul><li>Sources of Electricity (Main electricity and electric cells) </li></ul></ul><ul><ul><li>Define electric current and electric circuit </li></ul></ul><ul><ul><li>4 different parts of circuits and their symbols </li></ul></ul><ul><ul><ul><li>Connecting wires </li></ul></ul></ul><ul><ul><ul><li>Bulbs </li></ul></ul></ul><ul><ul><ul><li>Switch </li></ul></ul></ul><ul><ul><ul><li>Electric cell </li></ul></ul></ul>
  20. 20. Worksheet Complete the worksheet now
  21. 21. Today’s objectives <ul><li>At the end of this lesson, you will be able to: </li></ul><ul><ul><li>Understand what is complete and incomplete circuits </li></ul></ul><ul><ul><li>State the different types of switches in circuits </li></ul></ul><ul><ul><li>Understand how circuits can be arranged </li></ul></ul>
  22. 22. Complete and incomplete circuits <ul><li>Complete circuits is also known as closed circuits </li></ul><ul><li>Incomplete circuits is also known as opened circuits </li></ul><ul><li>What is the difference between the two? </li></ul>
  23. 23. Complete/Closed circuits <ul><li>It is complete path without any gaps from one end of the cell to the light bulb and back to the other end of the cell </li></ul>
  24. 24. Incomplete/Open circuits <ul><li>The path is incomplete </li></ul><ul><li>Each circuit has a gap in it and the bulbs do not light up </li></ul><ul><li>Example: no source of electrical energy or connecting wire is missing </li></ul><ul><li>See pg 55. </li></ul>
  25. 25. Try Inquiry Time pg 55 <ul><li>Circuit D </li></ul><ul><li>A: Place a connecting wire on each side of the cell </li></ul><ul><li>B: Place a connecting wire on each side of the light bulb </li></ul><ul><li>C: Place a connecting wire from the bulb and the cell on each side of the cell </li></ul>
  26. 26. Using symbols to draw circuit diagrams <ul><li>Page 56 </li></ul><ul><li>Try inquiry time </li></ul><ul><li>Circuit A. However the extra line between the two cells is not necessary. Circuit B is different as the light bulb is situated between the two cells </li></ul>
  27. 27. Types of Switches <ul><li>A switch is used to open or close a circuit. </li></ul><ul><li>Tap key switch </li></ul><ul><li>A plug switch </li></ul><ul><li>A mains switch used in buildings </li></ul><ul><li>When switch is off, the circuit is opened and the bulb will not light up </li></ul><ul><li>When switch is on, the circuit is closed and the bulb will light up </li></ul>
  28. 28. Types of Switches Ask and Learn
  29. 29. Conductors and Insulators Ask and Learn
  30. 30. How circuit can be arranged? <ul><li>Series circuit </li></ul><ul><li>Parallel circuit </li></ul>
  31. 31. Series Circuit <ul><li>The three light bulbs are arranged in series </li></ul><ul><li>Each component is joined one after the other to form a single path </li></ul><ul><li>Current flows through each component is the same </li></ul>
  32. 32. Series Circuit <ul><li>If one bulb in a series circuit is removed or broken, no current flows </li></ul><ul><li>The remaining bulbs do not light up </li></ul><ul><li>Because the circuit is opened </li></ul>
  33. 33. Parallel Circuit <ul><li>Any amount of light bulbs are arranged in parallels </li></ul><ul><li>Divides two or more branches and has electrical components in each branch </li></ul>
  34. 34. Parallel Circuit <ul><li>The current from the battery divides and flows through each branch </li></ul><ul><li>If one bulb breaks or removed, other bulbs on the circuit remain lit </li></ul><ul><li>Because the circuit remains closed </li></ul>
  35. 35. Series and Parallel Circuit Ask and Learn
  36. 36. Do Check Point Page 59
  37. 37. Objectives <ul><li>At the end of this lesson, you will be able to: </li></ul><ul><ul><li>Understand what is electric current and how to measure electric current </li></ul></ul><ul><ul><li>Understand what is voltage and how to measure voltage </li></ul></ul><ul><ul><li>State the different voltages for different sources </li></ul></ul><ul><ul><li>Understand how electric cells are connected in electrical appliances </li></ul></ul>
  38. 38. Electric Current <ul><li>Flow of electric charges </li></ul><ul><li>This flow of electrons in one directions in a circuit is called an electric current </li></ul><ul><li>Electrons require energy in order to move </li></ul><ul><li>Energy come from the electric cell in the circuit </li></ul><ul><li>Electric cell has two terminals </li></ul>
  39. 39. Electric Current <ul><li>Positive and negative </li></ul><ul><li>Pushes electrons out of the negative terminal and round the circuit </li></ul><ul><li>Flow back to the positive terminal of the cell </li></ul><ul><li>Electrons are not used up only energy is used up </li></ul>
  40. 40. Video on Electric Current Short video
  41. 41. Measuring Electric Current <ul><li>Ammeter </li></ul><ul><li>SI unit for electric current is ampere (A) </li></ul><ul><li>1A = 1000 mA </li></ul><ul><li>1mA = 0.001A </li></ul><ul><li>Connected in series </li></ul>
  42. 42. Measuring Electric Current
  43. 43. Ask and Learn Measuring Electric Current
  44. 44. What is Voltage? <ul><li>To measure the energy the electrons receive </li></ul><ul><li>An electron can have a large amount of potential energy at one point in the circuit </li></ul><ul><li>It can also have a low amount of potential energy at another point </li></ul><ul><li>The difference in potential energy between the two points is known as voltage </li></ul>
  45. 45. What is Voltage? <ul><li>SI unit for voltage is volt (V) </li></ul>
  46. 46. Measuring Voltage <ul><li>Voltmeter </li></ul>
  47. 47. Voltmeter <ul><li>Connected in parallel across the cell </li></ul><ul><li>Has positive (red) terminal and a negative (black) terminal like ammeter </li></ul><ul><li>Positive terminal connected to the positive side of the cell </li></ul><ul><li>Negative terminal connected to the negative side of the cell </li></ul>
  48. 48. Measuring Voltage <ul><li>Voltmeter </li></ul>
  49. 49. Different voltage for different electric sources <ul><li>Different electric cell have different voltage </li></ul><ul><li>In Singapore the main voltage is 230V </li></ul>1.5V 9V 12V
  50. 50. How are electric cells connected in electrical appliances? <ul><li>Electric cells are connected in series with the positive terminal of one cell touching the negative terminal of the next cell </li></ul><ul><li>The total voltage across all the electric cells is equal to the sum of the voltages of the individual cells </li></ul>
  51. 51. How are electric cells connected in electrical appliances? <ul><li>For example you have electric cell of 1.5V </li></ul><ul><li>If the toy need 9V to work. </li></ul><ul><li>You will need six 1.5V electric cells </li></ul>
  52. 52. Checkpoint Page 63
  53. 53. Objectives <ul><li>At the end of this lesson you will be able to: </li></ul><ul><ul><li>State what is a resistor </li></ul></ul><ul><ul><li>Understand the different types of resistors </li></ul></ul><ul><ul><li>Understand how resistors is placed in series and parallel arrangements </li></ul></ul>
  54. 54. What is a resistor? <ul><li>Appliances need to ensure that the correct size of current flows to operate properly </li></ul><ul><li>To control the size of the current, electrical components called resistors are used in the circuits </li></ul>
  55. 55. Resistors AsknLearn
  56. 56. Types of resistors <ul><li>Fixed </li></ul><ul><li>Variable </li></ul>
  57. 57. Fixed Resistors <ul><li>One fixed resistance </li></ul><ul><li>Resistance can be a fraction of an ohm to thousands of ohms </li></ul><ul><li>SI unit is ohms </li></ul>
  58. 58. Variable Resistors <ul><li>Known as rheostat </li></ul><ul><li>Vary the resistance in a circuit </li></ul><ul><li>Resistance change, the current also changes </li></ul><ul><li>When resistance decreases, the current increases </li></ul>
  59. 59. Rheostats <ul><li>Different types for different purposes </li></ul>
  60. 60. Fixed and Variable Resistor AsknLearn
  61. 61. Arrangement of resistors <ul><li>Can be in series or parallel </li></ul><ul><li>Series </li></ul><ul><ul><li>Same current from the electric cell passes through each resistor </li></ul></ul><ul><ul><li>As more resistors are added, the resistance to flow electrical charges increases </li></ul></ul><ul><ul><li>The current in the circuit decreases </li></ul></ul><ul><ul><li>Overall resistance in series circuit increases </li></ul></ul>
  62. 62. Arrangement of resistors <ul><li>Parallel </li></ul><ul><ul><li>For resistors in parallel, current from the electric cell divided among the resistor </li></ul></ul><ul><ul><li>More resistors added more electrical charges are able to flow through the resistors at the same time </li></ul></ul><ul><ul><li>Current in circuit increases </li></ul></ul><ul><ul><li>Overall resistance of the parallel circuit decreases </li></ul></ul>
  63. 63. Metal with… <ul><li>Low resistance </li></ul><ul><ul><li>Copper and silver </li></ul></ul><ul><li>High resistance </li></ul><ul><ul><li>Nichrome </li></ul></ul>
  64. 64. Resistor – Series and Parallel AsknLearn
  65. 65. Checkpoint Page 67
  66. 66. Objectives <ul><li>At the end of this lesson, you will be able to: </li></ul><ul><ul><li>State the heating effects and examples </li></ul></ul><ul><ul><li>Understand what is electromagnets and its uses </li></ul></ul><ul><ul><li>Understand what is chemical effects and electroplating </li></ul></ul>
  67. 67. Effects of Electric Current <ul><li>Heating effect </li></ul><ul><li>Magnetic effect </li></ul><ul><li>Chemical effect </li></ul>
  68. 68. Heating Effect <ul><li>Resistance in circuit wires affects the amount of electric current flowing </li></ul><ul><li>Electric current flows through the wire, the wire gets heated up </li></ul><ul><li>Electrical energy to heat energy </li></ul>
  69. 69. Heating Effect <ul><li>Heating element in an electrical appliance consists of high resistance wires such as nichrome </li></ul><ul><ul><li>Very hot </li></ul></ul><ul><ul><li>Produce more heat </li></ul></ul><ul><li>Connecting wires are made of low resistance materials such as copper </li></ul><ul><ul><li>Less hot </li></ul></ul><ul><ul><li>Produce less heat </li></ul></ul>
  70. 70. Heating Effect <ul><li>If resistance wire gets very hot, light can also be produced </li></ul><ul><li>Example: Filament of an electric light bulb </li></ul>
  71. 71. Magnetic Effect <ul><li>Electric current also produces magnetic effect </li></ul><ul><li>Example: placing wire near compass needle and let electric current flow, the needle will move </li></ul>
  72. 72. Magnetic Effect <ul><li>Electromagnet </li></ul><ul><ul><li>Coil of wire usually wound around a piece of iron </li></ul></ul><ul><ul><li>When current flows, it acts like a bar magnet </li></ul></ul><ul><ul><li>If no current flow, the electromagnet loses its magnetism </li></ul></ul>
  73. 73. Magnetic Effect <ul><li>Electromagnet </li></ul><ul><ul><li>How to make it stronger? </li></ul></ul><ul><ul><ul><li>Increase the current in the coil </li></ul></ul></ul><ul><ul><ul><li>Increase the number of turns of wire in the coil </li></ul></ul></ul><ul><ul><ul><li>Winding the coil around an iron core </li></ul></ul></ul>
  74. 74. Magnetic Effect <ul><li>Electromagnet </li></ul><ul><ul><li>Uses </li></ul></ul><ul><ul><ul><li>Magnetic cranes </li></ul></ul></ul><ul><ul><ul><li>Electric bells </li></ul></ul></ul><ul><ul><ul><li>Electric motors </li></ul></ul></ul>
  75. 75. Chemical Effect <ul><li>Electrolysis </li></ul><ul><ul><li>Uses </li></ul></ul><ul><ul><ul><li>Electroplating </li></ul></ul></ul><ul><ul><ul><li>Extraction of some metals </li></ul></ul></ul>
  76. 76. Electroplating Watch video
  77. 77. Chemical Effect <ul><li>Extraction of metals </li></ul><ul><ul><li>Solid compound of the metal is heated until it melts </li></ul></ul><ul><ul><li>An electric current is then passed through the molten compound </li></ul></ul><ul><ul><li>Molten compound break down to give the metal </li></ul></ul>
  78. 78. Do Checkpoint Page 72