Chapter 13 Current And Circuits

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Chapter 13 Current And Circuits

  1. 1. Chapter 13 Electric Currents and Circuits
  2. 2. Goal 1 Explain differing charges and factors that affect electric force
  3. 3. <ul><li>The Rule that Governs Electric Charges: </li></ul><ul><ul><li>Electric charge depends on imbalance of protons and electrons </li></ul></ul><ul><ul><li>Results in either a net + charge or net –charge </li></ul></ul><ul><ul><li>Like charges repel </li></ul></ul><ul><ul><li>Opposite charges attract </li></ul></ul>
  4. 4. <ul><li>Conductors allow charges to flow </li></ul><ul><li>Insulators do not allow charges to flow </li></ul>
  5. 5. <ul><li>Transfer of electrons can charge objects </li></ul><ul><ul><li>Friction </li></ul></ul><ul><ul><ul><li>Balloons can become negatively charged </li></ul></ul></ul><ul><ul><ul><li>Wool can become positively charged </li></ul></ul></ul><ul><ul><li>Contact </li></ul></ul><ul><ul><ul><li>Will result in a transfer of charges (see fig. 13-3) </li></ul></ul></ul>
  6. 6. <ul><li>Electric force depends on </li></ul><ul><ul><li>Charge: product of charges (multiply) </li></ul></ul><ul><ul><li>Distance: inversely proportional to the square of the distance </li></ul></ul><ul><ul><ul><li>This means further distances will dramatically reduce the electric force </li></ul></ul></ul>
  7. 7. <ul><li>13.1 Activity </li></ul><ul><ul><li>“Quick Activity” found on page 434 </li></ul></ul><ul><ul><li>Answer #5 in paragraph form with three sketches in your notebook </li></ul></ul><ul><ul><ul><li>Sketch 1: balloon and balloon with charges shown </li></ul></ul></ul><ul><ul><ul><li>Sketch 2: balloon and wall with charges shown </li></ul></ul></ul><ul><ul><ul><li>Sketch 3: balloon and water with charges shown </li></ul></ul></ul><ul><ul><li>(see figures 13-4 and 13-5 for assistance) </li></ul></ul>
  8. 8. Goal 2 Explain how batteries are a source of voltage
  9. 9. <ul><li>Voltage </li></ul><ul><ul><li>Potential difference </li></ul></ul><ul><ul><li>“-” and “+” battery terminals (electrodes) </li></ul></ul><ul><ul><li>Determines electron flow (electrolyte) </li></ul></ul>
  10. 10. <ul><li>Current </li></ul><ul><ul><li>Terminal connection </li></ul></ul><ul><ul><li>Electrons can flow </li></ul></ul><ul><ul><li>Movement of charge </li></ul></ul>
  11. 11. Goal 3 Explain resistance and use the resistance equation
  12. 12. <ul><li>Resistance </li></ul><ul><ul><li>Internal friction </li></ul></ul><ul><ul><li>Determined by </li></ul></ul><ul><ul><ul><li>Voltage across conductor </li></ul></ul></ul><ul><ul><ul><li>Current through the conductor </li></ul></ul></ul>
  13. 13. <ul><li>Resistance equation (triangle) </li></ul><ul><li>Resistance = Voltage </li></ul><ul><li>Current </li></ul><ul><li>R = V </li></ul><ul><li>I </li></ul>
  14. 14. <ul><li>Resistance units </li></ul><ul><ul><li>Ohms </li></ul></ul><ul><ul><li>Or </li></ul></ul><ul><ul><li>Volts </li></ul></ul><ul><ul><li>ampere </li></ul></ul>
  15. 15. <ul><li>Practice problems </li></ul><ul><ul><li>Pg 443 # 1-4 </li></ul></ul>
  16. 16. <ul><li>Superconductors </li></ul><ul><ul><li>0 resistance at specific temperatures </li></ul></ul><ul><li>Conductors </li></ul><ul><ul><li>Low resistance </li></ul></ul><ul><li>Semi conductors </li></ul><ul><ul><li>Will conduct when combined with other materials </li></ul></ul><ul><li>Insulators </li></ul><ul><ul><li>High resistance </li></ul></ul>
  17. 17. Goal 4 Use schematic diagrams to represent circuits
  18. 18. <ul><li>Circuit </li></ul><ul><ul><li>A path for an electrical current to travel </li></ul></ul><ul><ul><li>Closed circuit = complete path = current </li></ul></ul><ul><ul><li>Open circuit = incomplete path = no current </li></ul></ul>
  19. 19. <ul><li>Schematic diagram </li></ul><ul><ul><li>Symbols used to represent electric components </li></ul></ul><ul><ul><li>Copy symbols from Page 448 </li></ul></ul><ul><ul><li>**symbols may vary slightly depending on regions </li></ul></ul>
  20. 20. Goal 5 Explain the difference between series and parallel circuits
  21. 21. <ul><li>Series circuit </li></ul><ul><ul><li>One path for current flow </li></ul></ul><ul><ul><li>Loss of one component = open circuit uh-oh! </li></ul></ul>
  22. 22. http://www.bbc.co.uk/schools/ks3bitesize/science/physics/electricity_4.shtml
  23. 23. <ul><li>Parallel circuit </li></ul><ul><ul><li>More than one path for current flow </li></ul></ul><ul><ul><li>Loss of component is OK </li></ul></ul><ul><ul><ul><li>Another path </li></ul></ul></ul>
  24. 24. http://www.bbc.co.uk/schools/ks3bitesize/science/physics/electricity_4.shtml
  25. 25. Goal 6 Use the electric power equation
  26. 26. <ul><li>Power = Current x Voltage </li></ul><ul><li>P = I x V </li></ul><ul><li>Power given in “watts” </li></ul><ul><li>Current given in “amps” </li></ul><ul><li>Voltage given in “volts” </li></ul>
  27. 27. <ul><li>Practice problems </li></ul><ul><ul><li>Page 451 #1 - 5 </li></ul></ul>
  28. 28. Goal 7 Explain how fuses and circuit breakers prevent electric overload
  29. 29. <ul><li>Fuses </li></ul><ul><ul><li>Too much current = heat </li></ul></ul><ul><ul><li>Fuse melts </li></ul></ul><ul><ul><li>Circuit opens </li></ul></ul><ul><ul><li>Current stops </li></ul></ul><ul><ul><li>Fuse will need replacement </li></ul></ul>
  30. 30. <ul><li>Circuit breakers </li></ul><ul><ul><li>Magnets </li></ul></ul><ul><ul><li>Bi-metallic strips </li></ul></ul><ul><ul><li>Switch opens circuit </li></ul></ul><ul><ul><li>Reset circuit by closing switch </li></ul></ul>

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