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

51. Ohm’s Law
Ohm’s Law- the relationship between resistance, current and potential difference.
For a given potential difference, as the resistance increases, the current decreases

52. Another way to look at resistance..
The flow of electrons can be compared to people running an obstacle course
More obstacles= runners moving slower through the course
Wider course=more runner able to go through at the same time

53. Electron flow link
The amount of resistance in a circuit affects the amount of current(electrons) that can flow through it
More obstacles, slower flow of electrons
Wider= more electrons can flow through
# of loads= more loads means more resistance

54. Factors that can increase resistance
Connecting more loads in series
Connecting loads in series rather than parallel
Making the conductor longer
Making the conductor thinner
Using material with a high resistance

55. Ohm’s formula