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PHYSICS UNIT 3: SCHOOL ASSESSED COURSEWORK #2
REPORT ON A GENERATING SYSTEM
Answer the questions in the spaces supplied (marks in
brackets):
1. Explain why the step-up transformer is used to boost voltage
from 20kV to 220kV
at Yallourn W power station.
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2. The primary and secondary coils of a power line transformer
have 60 and 30,000turns respectively. Neglecting energy losses, if
240V AC is applied to the primary,
what will be the voltage in the secondary.
-------------V (2)
2. The figure below represents an ideal transformer, with 1000
turns on the primary
and two secondary coils, used in an overhead projector.
(i)There are 100 turns in the coil connected to the fan. What
voltage is on the fan?
_______V(2)
(ii) The globe is rated at 150W. It draws 6A when on.
(a) What is the voltage supplied to the globe? _______V (2)
(b) How many turns are in the secondary coil? _____turns (2)
3. The output of a 220kW power station is 5,500V. The
transmission lines have a
resistance of 5.0 ohms.
(a) What is the current in the lines? ________A (2)
(b) How much power is lost in the lines? ________W (2)
(c) What voltage reaches the town? ________V (2)
(d) The output voltage is now stepped up to 110 kV. What
percentage of the power
will now be lost?
_______% (3)
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4. An AC Voltmeter is used to measure the voltage between pairs
of pins in a power
point.
a) With the power point switch off, what would be the voltage
between
i) Active and neutral? ______V
ii) Active and earth? ______V
iii) Neutral and earth? _____V (3)
(b) With the switch on what are the above voltages? A-N _____V,
A-E _____V,
N-E _______V. (3)
5. Explain the function and the importance of:
a) Earth wires in buildings(2)
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b) Circuit breakers: (2)
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c) Double insulation: (2)
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6. Explain what happens when a person touches a "live" wire and
why this is
dangerous. (2)
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7. Explain how an induction cooktop works and what are two
advantages of these.(3)
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8. If 24 hours of power demand for Victoria is represented by
the following graph,
calculate the total energy used.
MW
50
25
12 midnight noon 12 midnight
___________J(3)
8. (a)What kind of power stations provide the bulk of Victoria's
power?
______________(1)
b) How do they work?
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_______________________________________________________________(3)
c) Describe two environmental problems with this method of power
generation.
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d) What two things can be done to lessen the environmental
problems in terms of
producing power?
_______________________________________________________________(2)
e) What kind of power stations take up the fluctuating demand
during the day?
__________________________(1)
9. Discuss this statement "Hydroelectric power is the best for
the environment".
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10. Name two methods for saving power usage in each of
(a)Public
buildings:_______________________________________________(2)
(b) Homes:
______________________________________________________(2)
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11. Give a description of what you think should happen in terms
of government
policies in the twenty-first century regarding electric power
generation, home-
building, appliance usage, public buildings, energy alternatives
etc, to improve our
environment and help alleviate global problems such as
greenhouse warming and
ozone-layer destruction.
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__________________________________________________________________(7)
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