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# E4 Introducing Electricity Part 3

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### E4 Introducing Electricity Part 3

1. 1. Watch this video
2. 2. <ul><li>For electricity to flow in a circuit, electrons in the copper atoms of the wires must move from one atom to the next. </li></ul><ul><li>This flow of electron in one direction in a circuit is called an electric current. </li></ul>What is an electric current?
3. 3. Electron flow in a circuit
4. 4. <ul><li>Energy is needed for the electron to move. </li></ul><ul><li>Source of energy: electric cell in the circuit </li></ul><ul><li>Electric cell has: </li></ul><ul><ul><li>a positive terminal, and </li></ul></ul><ul><ul><li>a negative terminal </li></ul></ul><ul><li>Electrons flow out of the negative terminal of the electric cell, round the circuit and back to the positive terminal of the cell. </li></ul>Path of electron flow
5. 5. <ul><li>Have you heard of ‘static’ electricity? </li></ul><ul><li>It is produced when certain materials, like wool and plastics, are rubbed against each other. </li></ul><ul><li>The rubbing process caused electrons from the surfaces of one materials to be transferred to the surface of the other material. </li></ul><ul><li>Have you experienced a shock from static electricity before? Recall how the static electricity could have been produced. </li></ul>Do you know?
6. 6. <ul><li>By using an ammeter </li></ul><ul><li>SI unit: ampere (A) </li></ul><ul><ul><li>Name after French scientist: Andre-Marie Ampere </li></ul></ul><ul><li>Other units: milliamperes (mA) </li></ul><ul><ul><li>1 A = 1000 mA </li></ul></ul><ul><ul><li>1 mA = 1/1000 A (or 0.001 A) </li></ul></ul>Measuring the size of an electric current
7. 7. <ul><li>Connected in series in a circuit </li></ul><ul><li>Ammeter has: </li></ul><ul><ul><li>A positive (red) terminal </li></ul></ul><ul><ul><li>A negative (black) terminal </li></ul></ul><ul><li>Positive terminal is connected to the positive side of the cell </li></ul><ul><li>Negative terminal is connected to the negative side of the cell </li></ul>Connecting an ammeter to a circuit
8. 8. <ul><li>Also called the potential difference </li></ul><ul><li>An electric cell provides electrical potential energy, thus pushing the electrons the circuit. </li></ul><ul><li>An electron can have a large amount of potential energy at one point in the circuit and a low amount of potential energy at another point in the circuit. </li></ul><ul><li>The difference in potential energy between the two points is the voltage. </li></ul>What is voltage
9. 9. <ul><li>By using a voltmeter </li></ul><ul><li>SI unit: volt (V) </li></ul><ul><ul><li>Named after Italian scientist: Alessandro Volta </li></ul></ul>Measuring voltage
10. 10. <ul><li>In a circuit, electrical components (eg. light bulbs) change some of the electrical energy into other forms of energy. </li></ul><ul><li>The electrons have less potential energy after passing through the component. </li></ul><ul><li>Hence, there is a difference in potential energy or a potential difference . </li></ul>Why is there a potential difference?
11. 11. <ul><li>Connected in parallel in a circuit </li></ul><ul><li>Voltmeter has: </li></ul><ul><ul><li>A positive (red) terminal </li></ul></ul><ul><ul><li>A negative (black) terminal </li></ul></ul><ul><li>Positive terminal is connected to the positive side of the cell </li></ul><ul><li>Negative terminal is connected to the negative side of the cell </li></ul>Connecting a voltmeter to a circuit
12. 12. <ul><li>Different electric sources have different voltages. </li></ul><ul><li>Example: </li></ul><ul><ul><li>A 9 V electric cell supplies 6 times the energy of a 1.5 V electric cell </li></ul></ul><ul><ul><li>Mains voltage is much greater. </li></ul></ul><ul><ul><li>In Singapore, mains voltage is 230 V. </li></ul></ul>Voltages of electrical sources
13. 13. <ul><li>Different countries use different values of mains voltage to provide electricity to electrical appliances. </li></ul><ul><li>The voltage used range from 100 – 240 V </li></ul><ul><li>For example: (Values taken from Wikipedia) </li></ul><ul><li>Find out whether you can still charge your handphone if you travel to countries which use a different mains voltage from Singapore. </li></ul>Do you know? Country/City Voltage (V) Japan 100 Canada 120 Indonesia 127 and 230 Philippines, Hong Kong, South Korea 220 Australia, New Zealand 230
14. 14. <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>Total voltage across all the electric cells = sum of the voltages of the individual cells </li></ul>Connecting electrical cells to electrical appliances
15. 15. <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>Total voltage across all the electric cells = sum of the voltages of the individual cells </li></ul>
16. 16. Complete Theory WB Pg. 34 - 37 Visit the following website: http://www.article19.com/shockwave/oz.htm