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