1. Electric Circuits

2. Electric Current
Current ( I ) – the rate at which charge passes through a wire.
Units – C/s = Amperes (A)

3. Drift Velocity

4. There is 3A of current moving through a point on a wire
There is 3A of current moving through a point on a wire. How much charge passes that point in 30 seconds?

5. There is 3A of current moving through a point on a wire
There is 3A of current moving through a point on a wire. How much charge passes that point in 30 seconds?
90C

6. How long does it take a wire carrying a current of 10A to move 15C of charge?

7. How long does it take a wire carrying a current of 10A to move 15C of charge?

8. Types of Current
DC – charges move only in one direction.

9. Types of Current
AC – the motion of charges continuously changes in the forward and reverse directions.

10. Conditions Necessary for Current
Complete Circuit
A closed path which charged particles move along.

11. Conditions Necessary for Current
2. Potential difference between two points in the circuit.
May be supplied by a battery (has + and – terminals)

12. Conditions Necessary for Current
3. Conductive material through which charge can move.
Metals are good conductors because their electrons move easily.

13. Conditions Necessary for Current
4. Resistance
If resistance were not present the circuit would overheat and burn out.

14. Resistance
Resistance ( R ) – the opposition that a device or conductor presents to the flow of electric current.
Unit – Ohm (Ω)

15. Factors that Effect Resistance
Less Resistance
More Resistance
Length
Cross-sectional area
Material
Temperature

16. Resistivity
Resistivity ( ρ ) – a measurement of how conductive a material is. (High resistivity means not as conductive)
Unit - Ω•m

17. R- Resistance (Ω) ρ- Resistivity (Ω·m) L- Length of wire (m) A- Cross-sectional Area (m2)

18. A 6. 5m long copper wire has a cross-sectional area of 3x10-3m2
A 6.5m long copper wire has a cross-sectional area of 3x10-3m2. What is the resistance in the wire?

19. A 6. 5m long copper wire has a cross-sectional area of 3x10-3m2
A 6.5m long copper wire has a cross-sectional area of 3x10-3m2. What is the resistance in the wire? R = 3.7x10-5Ω

20. A 0. 686m long wire has a cross sectional area of 8
A 0.686m long wire has a cross sectional area of 8.23x10-6m2 and a resistance of 0.125Ω. What is the wire made out of?

21. A 0. 686m long wire has a cross sectional area of 8
A 0.686m long wire has a cross sectional area of 8.23x10-6m2 and a resistance of 0.125Ω. What is the wire made out of? Nichrome

22. Ohm's Law
Ohms’s Law – the ratio of the potential difference to the current is always a constant for a given conductor and is called resistance.

23. Ohm's Law

24. Ohm's Law

25. Resistors
Resistor – a device used in a circuit to limit current flow or provide a potential drop.
Picture
Symbol

26. Variable Resistor – a coil of resistance wire whose effective resistance can be varied by sliding a contact point.
As more of the coil is used in the circuit, the resistance of the circuit increases, the current decreases.

27. Ammeters & Voltmeters in a Circuit

28. Ammeters & Voltmeters in a Circuit
Voltmeter – a device used to measure potential difference across a circuit.
Connect outside the direct path of the current (parallel connection)

29. Ammeters & Voltmeters in a Circuit
Ammeter – a device used to measure the current through a circuit.
Connect in the direct path of the current (series connection)

31. Overload
If a 1 appears by itself on the far left the multimeter has overloaded.
Try going to a higher setting
If at highest setting, record Overload or OL on lab

32. A Simple Circuit Model
A Water Analogy

33. What is a cell?
A cell (wet or dry), a contained area that releases energy due to a chemical reaction.
A cell stores charges.

34. How is a battery different from a cell?
A battery is just two or more cells wired together.

35. What is the difference between a D and AA cell?
Both cells do 1.5 J of work for each Coulomb of charge moved from one side to the other
However, a D cell stores more coulombs of charge, so it will last longer and do more work overall.

36. Battery Terminals

37. Two Types of Current

38. Two Types of Current

39. Drawing Circuit Schematic Diagrams
Circuit Schematic – a diagram of an electric circuit using standard symbols for the circuit elements.

40. Steps for Drawing Schematic Diagrams
Begin by drawing the symbol for the battery or other source of electric energy (such as a cell or generator).

41. Steps for Drawing Schematic Diagrams
2. Draw a wire coming out of the power source.
Draw wires as straight lines (use a ruler if needed)

42. Steps for Drawing Schematic Diagrams
When the path of the current reaches a resistor or other device, draw the appropriate symbol with values.

43. Steps for Drawing Schematic Diagrams
4. Follow the current path until you reach the other terminal of the battery.

44. Drawing Circuit Schematic Diagrams

45. 3.0 Ω
1.5 V

47. Energy Transfer & Transformation

48. Power Power (P) – the rate of conversion of electrical energy.
Units – Watts (W)

49. Electrical Energy
Electrical Energy (W) – the energy made available by the flow of electrical charges through a conductor
Units – Joules (J)

50. Cost of Electrical Energy

51. Energy Transmission

52. (Potential Difference)
Quantity
Symbol
Unit
Formula
Resistance
Voltage
(Potential Difference)
Charge
Current
Power
Energy

53. Resistors in Series Circuits
Characteristics
Series Circuit
Number of Paths
Current
Potential Difference (Voltage)
Total Resistance
Power
Disconnecting one bulb

54. Resistors in Parallel Circuits
Characteristics
Parallel Circuit
Number of Paths
Current
Potential Difference (Voltage)
Total Resistance
Power
Disconnecting one bulb

55. Influencing the Flow Rate (Current) on a Tollway

56. Resistors in Series Circuits

57. Resistors in Series Circuits

58. Resistors in Series Circuits

59. Resistors in Parallel Circuits

60. c. Fill in the current in the eight blank spaces in the view of the same circuit shown above.

61. 3. Cross out the circuit below that is not equivalent to the circuit above.

62. Circuit Segments
Segment – part of a circuit with two or more resistors

63. Circuit Segments

64. Circuit Switches
In which, if any, of the circuits below will the lamp light when switch S is closed?

65. Junctions Junction – a point where two or more current paths join.
Junction B
Junction C

66. Junctions
Kirchoff’s Junction Rule - The total current directed into a junction must equal the total current directed out of the junction.
Junction D
Junction E
Junction F