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Measuring Energy

Measuring Energy. Electric Current. Electric Current. Current: the rate of flow of electrons past a certain point in a circuit. Electric Current. Current: the rate of flow of electrons past a certain point in a circuit C urrent = C ounting electrons. Electric Current.

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Measuring Energy

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  1. Measuring Energy

  2. Electric Current

  3. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit

  4. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons

  5. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons • Ampere (A): the unit of electric current

  6. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons • Ampere (A): the unit of electric current • e.g. a 15A breaker opens the circuit when there are 15A of electrons flowing through the wires

  7. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons • Ammeter: a device used to measure current

  8. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons • Ammeter: a device used to measure current • -an ammeter is always placed in series

  9. Electric Current • Current: the rate of flow of electrons past a certain point in a circuit • Current = Counting electrons • Ammeter: a device used to measure current • -an ammeter is always placed in series

  10. Electric Current Which scale do you read?

  11. Electric Current Which scale do you read?

  12. Electric Current Estimate the reading:

  13. Electric Current Estimate the reading: between 150 and 200

  14. Electric Current Estimate the reading: between 150 and 200 What is each marking worth?

  15. Electric Current Estimate the reading: between 150 and 200 What is each marking worth? 5

  16. Electric Current Estimate the reading: between 150 and 200 What is each marking worth? 5 Final Answer?

  17. Electric Current Estimate the reading: between 150 and 200 What is each marking worth? 5 Final Answer? 175

  18. Electric Current Which scale do you use? Estimate the reading: between? What is each marking worth? Final Answer?

  19. Electric Current Which scale do you use? Estimate the reading: between? What is each marking worth? Final Answer?

  20. Electric Current Which scale do you use? Estimate the reading: between? 20 and 40 What is each marking worth? Final Answer?

  21. Electric Current Which scale do you use? Estimate the reading: between? 20 and 40 What is each marking worth? 2 Final Answer?

  22. Electric Current Which scale do you use? Estimate the reading: between? 20 and 40 What is each marking worth? 2 Final Answer? 32

  23. Potential Difference

  24. Potential Difference • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit

  25. Potential Difference • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit • Volt (V): the unit of potential difference

  26. Potential Difference • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit • Volt (V): the unit of potential difference • Voltmeter: a device used to measure potential difference

  27. Potential Difference • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit • Volt (V): the unit of potential difference • a voltmeter has to be connected in a parallel circuit

  28. Potential Difference looks like this...

  29. Potential Difference looks like this...

  30. Potential Difference an analogy: the waterfall

  31. Potential Difference an analogy: the waterfall Current: number of electrons

  32. Potential Difference an analogy: the waterfall Current: number of electrons =amount of water

  33. Potential Difference an analogy: the waterfall Current: number of electrons =amount of water Potential Difference: energy of the electrons

  34. Potential Difference an analogy: the waterfall Current: number of electrons =amount of water Potential Difference: energy of the electrons =height of the waterfall

  35. Resistance

  36. Resistance • Resistance: the ability of a material to oppose the flow of electrons through it

  37. Resistance • Resistance: the ability of a material to oppose the flow of electrons through it • Ohm (Ω): the unit of electrical resistance

  38. Resistance • Resistance: the ability of a material to oppose the flow of electrons through it • Ohm (Ω): the unit of electrical resistance • Ohmeter: a device used to measure electrical resistance

  39. Factors Affecting Resistance

  40. Factors Affecting Resistance 1. Type of Material: some materials have less internal resistance than others

  41. Factors Affecting Resistance 1. Type of Material: some materials have less internal resistance than others Insulators: resist the flow of electrons

  42. Factors Affecting Resistance 1. Type of Material: some materials have less internal resistance than others Insulators: resist the flow of electrons e.g. air plastic

  43. Factors Affecting Resistance 2. Length: the longer a wire is, the more electrical resistance the wire has

  44. Factors Affecting Resistance 2. Length: the longer a wire is, the more electrical resistance the wire has High voltage transmission lines: are used so fewer electrons have to travel through wires travelling long distances

  45. Factors Affecting Resistance 3. Thickness: a thick wire has less electrical resistance than a thin one. e.g. extension cords shouldn't be used permanently because they are usually thinner wires and can overheat

  46. Factors Affecting Resistance 4. Temperature: as temperature increases, its electrical resistance increases e.g. solenoid switches and furnace igniters

  47. Factors Affecting Resistance 4. Temperature: as temperature increases, its electrical resistance increases e.g. solenoid switches and furnace igniters -if igniter heats up, its resistance increases

  48. Factors Affecting Resistance 4. Temperature: as temperature increases, its electrical resistance increases e.g. solenoid switches and furnace igniters -if igniter heats up, its resistance increases -solenoid opens and gas is released & furnace lights

  49. Ohm’s Law

  50. Ohm’s Law • In 1827, Georg Ohm noticed a relationship between current, potential difference and resistance • After many experiments he noted that: • For a given resistance, as the electric potential difference across a load increases, so does the current

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