Gr. 9 Natural Science South Africa NCS syllabus. Taken from Andries Olivier.

1. Energy and
change

3. Mechanical
systems
to electrical

4. Van der graaff

7. dynamo

11. Alternative
sources

12. Electricity from
nonrenewable
sources

13. Coal

15. Electricity from
renewable
sources

16. Wind

19. Solar energy

22. Biomass/Biogas

24. Waterfalls

27. Geothermal

29. Wave energy

31. Tidal energy

35. Nuclear energy

38. cells

39. Store energy as chemical potential energy
This is converted to electric energy when the
battery/cell is connected to an appliance.
R
e
m
e
m
b
cell
battery

42. Inside the cell is a liquid called an
electrolyte.
Consist
of millions
of ions
Two electrodes
are
suspended
in the
electrolyte.
Two different
electrodes
cause a +
pole and a –
pole, just
like a battery.

43. How does a battery work?
Measured in volts
Electricity will
flow from the
– to the +
when a
circuit is
connected.
The difference
in charge
is called
potential
difference

44. There must be a potential difference in
an electric circuit for electricity to flow.

45. Wet and dry cells

46. The type of cell
in the previous
slides is
a wet cell.

47. The type of cell
in toys, radios
and torches
are called dry
cells.

48. Flow of current as
movement of charge.

49. Electric current is the movement of charge.

50. Direction
(Conventional current)

51. The flow of
positive charge
from the
positive pole
of a cell to the
negative pole
of a cell through an external conductor.

52. Electric current is the opposite and flows
from negative to positive.

53. We always use conventional current.

54. Coulomb
(unit of charge)

55. Does your
mum buy
milk by
the drop?

56. She buys it by the litre, because counting
the drops will take forever!

57. In the same way, we count electrons in
bundles. The unit of charge is thus a
large amount of electrons together, called
The coulomb.
1 coulomb = 6 250 000 000 000 000 000
= 6,25 x 1018
particles

58. The ammeter is
used to measure
how quickly charge
flows past a fixed
point in a conductor.

59. The ammeter is …
Always connected in series in a circuit.
Always connected positive to positive, and
negative to negative.

60. Ampere
(unit of current)

61. Q = It
Charge in
coulomb (C)
Current in
ampere (A)
Time in
seconds (s)

62. A coulomb is the amount of charge that flows
past a certain point in a conductor in one
second when the current that flows through it
is one ampere.

63. voltmeter

64. Potential difference
or electric charge -
Ability of a cell to
deliver electric
current.
Measured in volt (V)

65. The voltmeter is...
always connected in parallel.
connected positive to positive and
negative to negative.

66. A
V
V

67. Resistance

68. Things that allow current to flow through
them are called conductors.

69. Things that don't allow the flow of current
through them are called insulators.

70. Collisions between
the charges and the
particles of the
conductor obstruct
the flow of charge.
This is called
resistance.

71. Electrical resistance is the
Obstruction
a conductor offers against the
flow of charge.

72. Ohm's law

73. Potential difference (V), in a simple electric
circuit, is equal to the current strength (I)
multiplied by the resistance (R).

74. V = IR
Potential
difference (V)
Current in
ampere (A)
Resistance
in ohm (Ω)

75. Potential difference (V), in a simple electric
circuit, is equal to the current strength (I)
multiplied by the resistance (R).

76. Factors that
determine the
resistance of
a conductor
Andries p 165

77. Factors that influence the
resistance of a conductor:
Type
Length
Thickness
Temperature

78. Type

79. Length

80. Thickness

81. Temperature

82. Series
circuit

83. Parallel
circuit

84. If the potential difference
increases,
the current increases

85. If the resistance
increases,
the current strength
decreases

86. Main current
divides
between parallel
connected branches.
Ammeter readings are the
sameall over the circuit.
Current in series and parallel

87. Potential difference is the
sameeverywhere in a parallel
connection.
Potential difference
dividesbetween the resistors.
Pd in series and parallel

88. Increased
amount of
resistors
=
increased total
resistance
Increased
amount of
resistors
=
decreased
total resistance
Resistors in series and parallel

89. Increased
total resistance
Decreased
total resistance
Resistors in series and parallel

90. Current in each
resistor is the
same
Current divides.
Depends on the
magnitude of the
resistance
Resistors in series and parallel

91. Vt = V1 + V2 Vt = V1 = V2
Resistors in series and parallel