Download Marking Key – Electricity

Marking key
Electricity end-of-unit assessment
Objective items
1. A torch battery is connected to a torch globe by two wires. The globe is glowing and
giving out light.
Which is the best explanation for what happens to the electric current in the wires?
a. The electricity flows through wire A from the battery to the globe, which uses up all
the electricity. Wire B is not needed.
b. The electric current flows through both wires to the globe where it is used up.
c. The electric current flows through one wire to the globe where some of it is used up.
The remaining electric current flows through the other wire back to the battery.
d. The electric current flows round the circuit and none is used up by the globe, so that
the amount of current in the two wires is the same.
2. Which of the following lists include only conductors of electricity?
e. iron, wood and paper
f. nichrome, plastic and paper
g. mercury, copper and carbon
h. wood, plastic and paper.
3. Use the words from here (torch, battery, connecting wire, variable resistor, switch,
globe) to label the diagram below. (6 marks)
B
A
C
D
A is a battery (1)
C is a globe (1)
B is a connecting wire (1)
D is a switch (1)
Is the globe working and lit up? No (1)
Explain your answer The switch is open/in the off position (1)
 Commonwealth of Australia, 2003
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Marking key
Electricity end-of-unit assessment
4. In a house there are four lights connected into a circuit as shown in this diagram.
B
A
C
D
a. Where would you put a switch that would turn all the lights off?
i. A
ii. B
iii. C
iv. D.
b. Where would you put a switch that would turn one light off and leave three lights
on?
i. A
ii. B
iii. C
iv. D.
5. In which of the following circuits will the globe(s) be brightest?
A circuit containing:
a. one 2 V globe and one 1.5 V battery
b. two 2 V globes and one 1.5 V battery
c. two 2 V globes and two 1.5 V batteries
d. one 2 V globe and two 1.5 V batteries.
6. Which of the following wires is likely to have the greatest resistance?
a. A copper wire 0.2 mm thick and 10 cm long
b. A Nichrome wire 0.2 mm thick and 10 cm long
c. A Nichrome wire 0.1 mm thick and 15 cm long
d. A copper wire 0.3 mm thick and 5 cm long.
7. Which of the following electrical appliances will use the greatest amount of electrical
energy?
An appliance with a rating of:
a. 1,000 watts used for 3 hours
b. 1,500 watts used for 3 hours
c. 800 watts used for 4 hours
d. 500 watts used for 5 hours.
 Commonwealth of Australia, 2003
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Marking key
Electricity end-of-unit assessment
Extended response items
8. Four electrical circuits were constructed including a torch globe, a battery and either a
glass marble, an iron nail, a piece of aluminium foil or a pencil lead. (3 marks)
A
B
C
D
Globe
Glass marble
Iron nail
Aluminium foil
Pencil lead
a. Which of the globes will light up?
B, C and D (1)
b. Why would these globes light up?
Iron, aluminium and carbon pencil lead are all conductors of electricity. (1)
c. Why would the other globe(s) not light up?
Glass is not a conductor of electricity/it is an insulator. (1)
9. Some materials are conductors of electricity while others are insulators. (3 marks)
a. What are conductors used for? Explain using an example.
Conductors are used to carry/transmit electricity, eg connecting wires in a circuit. (1)
b. What are insulators used for? Explain using an example.
Insulators are used to stop the leakage of electricity to areas where it would cause a
problem, eg plastic covering on electrical wires. (1)
c. What property of a material determines whether it will allow electricity to flow though
it?
Electricity is carried through materials like metals that have electrons that are free to
move through the material. (1)
10. How is the amount of electricity flowing through a circuit affected by the number of
batteries in the circuit? (3 marks)
Increasing the number of batteries increases the amount of current. (1)
Increasing the number of batteries increases the voltage applied to the circuit and this
increases the current, doubling the voltage doubles the current. (2)
 Commonwealth of Australia, 2003
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Marking key
Electricity end-of-unit assessment
11. How is the amount of electricity flowing through a circuit affected by the number of
globes in the circuit? (3 marks)
Increasing the number of globes in a circuit reduces the amount of current. (1)
Increasing the number of globes in a circuit increases the resistance, doubling the
resistance halves the current. (2)
12. What is voltage and how does it affect the amount of current flowing through a circuit?
(4 marks)
Voltage is the electrical pressure that pushes current/electrons round a circuit. (1)
Chemical reactions within batteries create an excess of electrons at the negative
terminal of which pushes electrons through a circuit to the positive terminal of the
battery where there is a deficit of electrons; voltage is a measure of the electrical
pressure applied by the battery. (2)
Doubling voltage doubles current. (1)
13. What is resistance and how does it affect the amount of current flowing through a
circuit? (4 marks)
Resistance restricts/opposes the flow of current. (1)
Resistance is a property of a circuit component that restricts/opposes the flow of
electrons through that component eg in a wire the material, length and diameter all
affect the resistance of that wire. (2)
Doubling resistance halves the current. (1)
14. The Kelly family live in Alice Springs, which is hot in summer and cold in winter. Mr
and Mrs Kelly both work full time in normal office hours, five days per week. Children
Matthew, George and Katy all attend the local high school. The Kellys have an
electrical hot water system that heats water as it is used, they use electricity for
cooking and for air-conditioning, and they have a gas room heater in the living area of
their home. Consider the patterns of electricity consumption in the Kellys’ home. (9
marks)
a. Explain how electricity consumption will vary:
i. During a single working day ie Monday to Friday
More electricity will be used in the morning (eg showers, cooking) and evenings
(eg cooking and TV) than during the middle of the day when members of the
family are at work and school. (2)
ii. between week days and weekend days
More electricity will be used on weekend days than on weekdays as people will
be at home for longer periods of time using electricity for cooking, showers,
lighting and entertainments such as TV. (2)
iii. between summer and winter.
In summer electricity used for air-conditioning will add to consumption,
whereas gas is used for heating in winter – likely to use more electricity in
summer. (2)
b. What suggestions would you make to reduce the Kellys’ consumption of gas and
electricity?
In Australia, especially in inland locations like Alice Springs, there are wide
variations in ambient temperature between summer and winter and between day
 Commonwealth of Australia, 2003
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Marking key
Electricity end-of-unit assessment
and night. Insulation can be used to reduce heat loss and gain from a house,
reducing air-conditioning and heating costs (1), similarly curtains and other window
treatments can be used to reduce heat loss and gain through windows. (1)
Orienting a house appropriately on a block and use of verandas can reduce the sun
falling directly on windows in summer and thereby reduce air-conditioning costs. (1)
 Commonwealth of Australia, 2003
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