Download 1. Society has become increasingly dependent on

1. Society has become increasingly dependent
on electricity over the last 200 years
What do you know about the debate that took place
between Volta and Galvani about animal and chemical
electricity? How did it contribute to increased
understanding about electricity?
How have the main sources of domestic energy have
changed over time?
What are some of the impacts of changes in, and
increased access to, sources of energy for a community?
What are some of the ways in which electricity can be
provided in remote locations?
2. One of the main advantages of electricity
is that it can be moved with comparative ease from
one place to another through electric circuits
Behaviour of electrostatic charges and the field associated with them
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Do you know what a millicoulomb and
microcoulomb are? prefixes? sci.notation?
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Describe the electric field as a field of force
with a field strength equal to the
force per unit charge at that point:
E =F/q
F = qE
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200 V
700 V
F = mg
1. Which is the positive plate?
2. What direction would the electric field be?
3. Is this particle positively or negatively charged?
4. What two forces act on a charged particle between
the plates? Equations? Direction?
5. How can we change the strength of the field?
Current is the rate at which charge flows
(C/s or amperes) under the influence of
an electric field
Current can be either
direct with the net flow of charge carriers moving in one
direction (D.C.)
or
alternating with the charge carriers moving backwards
and forwards periodically
(A.C.)
Potential difference (voltage) between two points is
the change in potential energy per unit charge moving
from one point to the other (joules/coulomb or volts)
Discuss how potential difference between different
points around a circuit varies
10 A
12 W
R1
R2
240 V
R3
8 W
4 W
 Conductors have electrons in their atoms
which flow easily
 Insulators have outer electrons in their
atoms which do not flow easily
Solve problems and
analyse information applying
V = IR
10 A
12 W
240 V
R?
8 W
V = IR
VT = IT .RT
RT = VT / IT = 240/10 = 24 W
R = 24 - 12 - 8 = 4 W
3. Series and parallel circuits serve
different purposes in households
10 A
12 W
R1
R2
240 V
4 W
R3
8 W
•Resistors on one branch of circuit
•Total resistance RT = R1 + R2 + R3 ......
•Current is the same for each of resistors in series
•Voltage drops vary - use Ohm’s Law
10 A
240 V
R1
R2
R3
•Resistors on different branches of circuit
•Total resistance: 1/RT = 1/R1 + 1/R2 + 1/R3 ......
•Voltage is the same for each of resistors in parallel
•Current may vary - use Ohm’s Law
A
Ammeter always connected in series to read current THROUGH the resistor
V
Voltmeter always connected in parallel to read voltage ACROSS the resistor
Explain why there are different circuits
for lighting, heating and other appliances
in a HOUSE
 IF ONE CIRCUIT BLOWS, THE OTHERS DON’T
 THE MAIN DIFFERENCE IS HEAVIER GAUGE
WIRING IN POWER POINT AND HEATING
CIRCUITS (MORE CURRENT)
 IT FOLLOWS THAT POWER POINT AND HEATING
CIRCUITS HAVE LARGER CAPACITY FUSES AND
CIRCUIT BREAKERS
4. The amount of power is related to
the rate at which energy is transformed
What are the advantages and disadvantages of
labelling goods with power rating?
Why has a simple scale has been used for energy
rating on commercial goods and how do these scales
relate to potential difference and current?
Propose reasons as to why the kilowatt-hour is used to
measure domestic electricity consumption rather than the joule
You gathered first-hand information to estimate the cost
of electricity consumed by your household
Discuss ways in which consumption could be reduced
5. Electric currents also produce magnetic
fields and these fields are used in different
technologies in the home
Describe the behaviour of the magnetic poles when
they are brought close together
The direction of the magnetic field at a point is the direction
of force on a very small magnetic pole when placed at that
point
Describe the magnetic field around single magnetic poles
and pairs of magnetic poles
Compare the nature and generation of magnetic fields
by solenoids and a bar magnet
What was
involved
in these
experiments?
Describe the production of a magnetic field by an
electric current in a straight current-carrying
conductor and describe how the right hand grip
rule can determine the direction of current and
field lines
B
I
B
I
B
B
Assess the impact of applications of
magnetic fields on society
Explain one application of magnetic fields in
households, such as:
telephone or stereo speakers
magnetic tape
and use the available evidence to assess the
impact of its use
6. Safety devices are important in household
circuits
Discuss the effects of an electric shock from both a 240
volt AC mains supply and various DC voltages, from
appliances, on the muscles of the body
SEE
p.133-134
Jacaranda text
Identify the functions of circuit breakers,
fuses and other safety devices in the home
How are insulators
and earth wires used
in appliances?