Download File

August 2011 Answers
Part A: Multiple Choice Questions
Question 1
C
Question 2
A
Question 3
C
Question 4
B
Question 5
B
Question 6
B
Question 7
B
Question 8
C
Question 9
C
Question 10
D
Question 11
A
Question 12
D
Question 13
A
Question 14
A
Question 15
D
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 1
Part B: Constructed Response Questions
Question 16
Example of an appropriate response
Effect of loss
of producers
Justification
The population will
decrease.
As the producers have been destroyed by
the fire, there is a limited food supply for
the primary consumers and they may not
have enough food to survive. This effect
may be passed along the trophic levels.
There will also be increased competition for
food, compounding the problem. The
population may also decrease because the
consumers may have emigrated from the
area to escape the fire.
The population will
increase.
It is possible that many of the animals in
the ecosystem may die, providing more
food for the decomposers. An increased
food supply is favourable for an increase in
population.
Consumers
OR
The population will
Decomposers decrease.
The organic matter on the ground may
have been destroyed by the fire and the
animals in the conservation area may have
fled the fire. In this case, less food is
available for the decomposers. A decrease
in food supply leads to a decrease in the
population.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Effect is correctly identified and justification is appropriate and complete for both the
consumers and decomposers.
Effects are correctly identified and one complete justification and one partial
justification is provided.
Effects are correctly identified with two partial justifications provided or one effect
correctly identified and the justification for that effect is complete and appropriate.
One effect correctly identified and partially justified.
No relevant explanations given.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 2
Question 17
Example of an appropriate procedure
Note: Accept other conventional symbols.
Marking Scale
2 marks
1 mark
0 marks
Draws four correct elements (conductor, power supply, switch, light) connected in
series.
Draws two or three correct elements connected in series.
Fewer than two correct elements or no answer given.
V  13.7 V
I  2 .0 A
V  RI
3 .7 V
R
2. 0 A
 1.9  1.85  is also acceptable.
Marking Scale
2 marks
1 mark
0 marks
Appropriate calculations and correct answer.
Appropriate calculations, but calculation or transcription error or an incorrect or
missing unit in the answer.
No correct answers or no answers given.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 3
Question 18
Sample B is an ore.
Justification:
Example of an appropriate justification
Sample B is an ore because:

ores contain minerals that are of economic value.

sample B contains copper (in high concentrations) and copper has economic value.
Marking Scale
4 marks
2 marks
1 mark
0 marks
Sample correctly identified with an appropriate justification.
Sample correctly identified with a partially appropriate justification.
Sample correctly identified.
Sample incorrectly identified or no answer given.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 4
Question 19
Examples of appropriate responses
Accept aluminum, steel or fibreglass as an appropriate choice of material as long as it is well
justified. Examples of appropriate justification for each material are listed below.
Aluminum alloy:
-
Lightweight material therefore consumes less energy.
Easy to shape into the car panels.
Resistant to oxidation.
Steel:
-
Hardness and resilience of material ideal for resisting wear and tear on the car body from
rocks, weather.
Fibreglass:
-
Easy to shape into the car panels but may not give as much protection to passengers.
Good material as it is resistant to compression.
Lightweight.
Will not rust.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Provides a complete justification of the material to be used on the car’s body.
Provides appropriate justification, mentioning most of the elements involved.
Provides a partial justification, omitting certain elements.
Provides an inadequate justification of material.
Provides an incorrect justification or does not provide a justification.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 5
Part C: Technological Analysis
Question 20
Examples of appropriate responses
Uses the characteristics of the components of the gear system to explain how the speed
changes from the blades to the generator shaft.
Description:
-
Low-speed shaft (18 RPM)
Large gear diameter
High number of teeth (12)
Fewer rotations and slower speed of rotation
Driver
-
High-Speed shaft
Small gear diameter
Low number of teeth (6)
High number of rotations and high speed of rotation
Driven
Explanation:
-
The rotational guiding from the low-speed shaft turns a large gear with high number teeth,
therefore turning at a lower speed than the smaller gear attached to the high-speed shaft
which consists of fewer teeth, therefore turning at a high speed.
Marking Scale
4 marks
3 marks
2 marks
0 marks
Describes the characteristics of the gears, and provides a complete explanation of
the speed change.
Describes the characteristics of the gears, and provides a partial explanation of the
speed change.
Describes the characteristics of the gears, but explanation of speed change is
incorrect or missing.
No answer or answer is incorrect.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 6
Question 21
Examples of appropriate responses
Mechanical Processes:
-
The blades of the wind turbine rotate the low-speed shaft.
The gear system increases the number of rotations from the low-speed shaft.
The high-speed shaft rotates the electromagnet in the generator.
Electrical Processes:
-
A magnetic field must be in motion relative to a charge or conductor.
Achieved through moving a magnet around a conductor.
-
The electric current is generated in the conductor by varying the speed of the magnetic
field.
-
The greater the number of rotations the greater the electric current created.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Describes the mechanical process and the electromagnetic induction principal
(i.e. rotation of the shafts and its effect on the electromagnet in the generator).
Completely describes one of the two processes (mechanical or electrical) and
partially describes the other.
Completely describes only one of the processes or partially describes both the
mechanical and electrical processes.
Partially describes one of the processes.
Does not answer or answers incorrectly.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 7
Question 22
Examples of appropriate responses
a)
Explains the choice of guide plate as a guiding control for the low-speed shaft.
The guide plate limits the translation motion of the low speed shaft.
Allows rotation of the low speed shaft.
b)
Using Bernoulli’s Principle, explains why the blades turn when wind is present.
The force of the wind applies uneven pressure on the blade.
The pressure on the blades is greater on one side and weaker on the other side.
There must be enough wind to create sufficient uneven pressure to move the blades.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Complete explanation for both the guiding control and Bernoulli’s Principle.
Complete explanation for the guiding control and a partial explanation for Bernoulli’s
Principle.
Partial explanation for the guiding control and a partial explanation for Bernoulli’s
Principle or complete explanation for the guiding control and explanation for
Bernoulli’s Principle incorrect or not given.
Partial explanation for one of the required components (Bernoulli’s Principle or
guiding control).
Does not answer or answers incorrectly.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 8
Question 23
Example of an appropriate procedure
1.
Find energy needed for one light bulb.
P
P
P
P
 VI
 120.0 V  2.0 A
 240 W
 0.24 kW
E  P  t
E  0.24 kW  1h
E  0.24 kW  h
1 light requires 0.24 kWh.
2.
Find number of lights that can be powered by 108.0 kWh.
1 light  0.24 kW  h
x light  108.0 kW  h
108.0 kW  h
x
0.24 kW  h
x  450
The number of lights that can be powered by the wind turbine is: 450 light bulbs.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Appropriate procedure and correct answer.
Appropriate procedure, but incorrect answer because of minor mistakes such as a
calculation or transcription error, an incorrect or missing unit of measure.
Appropriate procedure but incorrect answer because of major mistakes.
Partially appropriate procedure regardless of the answer.
Inappropriate procedure or did not show the procedure, regardless of the answer.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 9
Question 24
Examples of appropriate responses
Modification
Justification
Increase the number of turns of The number of turns of wire around the solenoid will
wire around the solenoid in the increase the magnetic field of the electromagnet in the
solenoid.
solenoid. As the wind turbine works using electromagnetic
induction, if we increase the magnetic field, the amount of
energy generated will also increase.
Use a ferromagnetic core in the Using a ferromagnetic core will increase the magnetic field of
solenoid.
the electromagnet in the solenoid. As the wind turbine works
using electromagnetic induction, if we increase the magnetic
field, the amount of energy generated will also increase.
Increase the number of magnets, As the wind turbine works using electromagnetic induction, if
or use stronger magnets in the we increase the magnetic field, the amount of energy
induction generator.
generated will also increase.
Accept any other appropriate answer.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Suggests two (2) appropriate modifications and two (2) appropriate justifications.
Suggests two (2) appropriate modifications and one (1) appropriate justification.
Suggests one (1) appropriate modification and an appropriate justification.
Suggests one (1) appropriate modification or one (1) appropriate justification.
Suggests incorrect modifications and justifications or does not suggest any at all.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 10
Question 25
Examples of appropriate responses
Modification
Make the blades more
aerodynamic.
Justification
By making the blades more aerodynamic, you will increase
the Bernoulli Effect that causes the blades to move faster,
thus leading the generator to have a higher amount of RPM,
and therefore generating more electricity.
In the gear system, replace driver By increasing the speed change (the gear ratio) it will cause
gear with a larger driver gear, the driven gear to turn faster resulting in the generator
and/or replace driven gear with a turning faster.
smaller driven gear.
Reduce the friction between the By reducing the friction we will be reducing the amount of
parts.
energy lost and thus increasing the energy efficiency of the
wind turbine.
Note: Accept all other appropriate responses.
Marking Scale
4 marks
3 marks
2 marks
1 mark
0 marks
Suggests two (2) appropriate modifications and two (2) appropriate justifications.
Suggests two (2) appropriate modifications and one (1) appropriate justification.
Suggests one (1) appropriate modification and an appropriate justification.
Suggests one (1) appropriate modification or one (1) appropriate justification.
Suggests incorrect modifications and justifications or does not suggest any at all.
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Page 11
Applied Science and Technology – 557-406
Secondary Cycle Two Year Two
Theory Examination
Administration and Marking Guide
Appendix