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Homework Booklet
National 5 Physics
Electricity and Energy Part 1
DO NOT write on this booklet.
You will be required to return it at the end of the course!
Last updated by AD May 2014
1
Practice questions on generation of electricity
1.
Give an example of how Scotland can produce electricity and an advantage and
disadvantage associated with that method of generation.
2.
Thermal power stations are used to produce electricity:
a) explain using the words steam, turbine and generator how a thermal power station
produces electricity
b) describe the energy changes in a thermal power station from the initial chemical store
of energy to the final production of energy being transferred electrically.
Practice questions on electrical power
(From HSDU Int2 Pupil Materials Pack)
3.
What is meant by the term power?
4.
Explain how the power rating of an appliance can be determined from the appliances
rating plate.
5.
How do increasing the following quantities affect the cost of using an appliances:
a) power rating of the appliance
b) time that the appliance is used for
c) cost per unit of electricity supplied by the electricity company
6.
A light bulb has a power rating of 60 W.
a) How much energy is transferred electrically by the bulb in 1 s?
b) State the energy transfers involved when the lamp is switched on.
7.
The electric motor on a ceiling fan transfers 207 kJ of energy electrically in 30 minutes.
a) Calculate the power rating of the motor in the fan.
b) State the energy transfers involved when the ceiling fan is switched on.
8.
How much energy is transferred electrically by the following appliances?
a) A 400 W drill used for 45 s
b) A 300 W food processor used for 20 s
c) An 800 W iron used for 40 minutes
d) A 2.4 kW kettle that takes 5 minutes to boil the water inside it.
9.
What is the power rating of an appliance which transforms a) 500 J in 5 s
b) 1200 J in 20 s
c) 1.8 MJ in 10 minutes?
10. How long would a 2 kW electric kettle take to boil the water inside if it transfers 100 kJ of
energy electrically?
11. What is meant by the term efficiency?
12. Why are systems that produce or use electricity not 100% efficient?
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13. What is the efficiency of a machine which has a power input of 800 W and a power output
of 600 W?
14. A machine which is 80% efficient transfers 20000 J of energy. What is its energy output?
15. A motor which is 60% efficient has an output power of 480 W. What is its input power?
Practice questions on electromagnetism
(From HSDU Int2 Pupil Materials Pack)
16.
Draw the magnetic field pattern around:
a) single bar magnet
b) two bar magnets being attracted to each other
c) two bar magnets repelling each other
17
a)
b)
Draw a diagram of an electromagnet.
The strength of the magnetic field, B, measured in Tesla (T) from the electromagnet can
be calculated using the formula:
In this formula I represents the current to the electromagnet (A) and d the distance from
the electromagnet (m).
Calculate the strength of an electromagnet with a current of 3A at a distance of 10cm
from the electromagnet.
18.
19.
20.
How can the strength of an electromagnet be increased?
a) Explain how a voltage could be induced in a coil of wire.
b) Give three methods of increasing the size of this induced voltage.
Draw a labelled diagram of a transformer.
21.
Give 3 uses of transformers in every day life.
22.
Explain why a transformer will only give a continuous output when used with a.c.
Practice questions on conservation of energy
(From HSDU Int2 Pupil Materials Pack)
23. a) If an electric current is passed through a conducting wire, what energy
transfer takes place?
b) Many electrical appliances in the home are designed to make use of this energy
transfer. Name four of these appliances.
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24. Copy and complete these examples of energy transfers.
a) Car moving at a steady speed along level road
chemical store of energy
->
b) Car accelerating along level road
chemical store of energy
->
+
c) Car braking
kinetic store of energy ->
d) Car free wheeling downhill ( engine switched off )
->
+
25. A chairlift raises a skier of mass 60 kg to a height of 250 m. How much energy is gained to be
stored potentially by the skier?
26.
A brick of mass 3 kg rests on a platform 25 m above the ground on a building site.
a) How much energy is stored potentially by the brick?
b) If the brick falls 25 m to the ground, how much stored energy will it lose?
c) What store will the energy be being transferred into as the brick falls?
27. Estimate how much energy you would gain if you were lifted 30m up to the top of a fun-ride.
28.
An apple, mass 100 g, has 300 J of energy stored potentially at the top of the Eiffel Tower.
a) What is the height of the Eiffel Tower?
b) How much energy would it have stored kinetically just before hitting the ground?
c) What will be its velocity as it hits the ground?
29. An astronaut of mass 70 kg climbs to a height of 5 m on the moon and gains 560 J of
energy. What must be the gravitational field strength on the moon?
30.
The energy, E, stored potentially in the elastic band can be calculated using the
formula:
E = 0.4 d2
Where d, measured in meters, is the distance that the elastic band is pulled back.
Calculate the velocity of release of a vehicle of mass 200g when it is pushed forwards
by an elastic band pulled back 20cm.
31. Calculate the energy stored kinetically by the following:
a) a 5 kg bowling ball moving at 4 ms-1
b) a 50 kg skier moving at 20 ms-1
c) a 0.02 kg bullet moving at 100 ms-1 .
32.
a) How much energy does a 800 kg car stored kinetically when travelling at a speed of
10 ms-1 ?
b) If it doubles its speed to 20 ms-1, Calculate the new amount of energy stored kinetically.
33. A cyclist who is pedalling down a slope reaches a speed of 15 ms-1 .
The cyclist and her cycle together have a mass of 80 kg.
a) Calculate the total energy stored kinetically.
b) Explain why the amount of energy stored kinetically increases as the cyclist pedals down hill.
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34. Calculate an approximate value for the energy stored kinetically an Olympic 100 m sprinter as
he crosses the line (time for race is about 10 s).
35. What is the speed of a stone of mass 2 kg if it has 36 J of energy stored kinetically?
36. A motor cyclist and his bike have a total mass of 360 kg and 87120 J of energy stored
kinetically. What is his speed?
Practice questions on electrical charge
carriers and electric fields
(From HSDU Int2 Pupil Materials Pack)
37. a) Explain what is meant by the term ‘electric current’.
b) Write down the relationship between charge and electric current.
c) Give the names of the units used to measure the three quantities.
38. One bar of an electric heater draws a current of 4 A from the mains supply.
a) How much charge flows through the bar each minute?
If a second bar is switched on, the charge flowing through the bar each minute
increases to 440 C.
b) Calculate the new current drawn from the mains when both bars are switched on.
39. The manufacturer of the battery in a car states that the battery is rated at 40 ampèrehours. This is one way of telling the user how long the battery will be able to provide electric
current to operate appliances.
eg. this could deliver 40 A for 1 hour or 8 A for 5 hours etc.
a) Calculate the total charge that this battery can deliver, in coulombs.
b) The parking lights of the car draw a current of 2 A from the battery. If these
lights were left on when the car was parked, calculate the minimum time it would take for
the battery to go flat.
c) State any assumption you are making in your answer to part b)
40. a)
b)
Explain the difference between a.c. and d.c. Your answer should state what is
represented by the terms a.c. and d.c. and include the words ‘electron’ and
‘direction’.
The maximum current, Imax, flowing in an a.c. circuit can be calculated using the
formula:
Where I is the current measured directly with an ammeter.
Calculate the maximum current flowing in an a.c. circuit if the ammeter reading in the
circuit is 3A.
41. Give two examples each of
a) a.c. power supplies
b) d.c. power supplies.
Last updated by AD May 2014
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Practice questions on potential difference
(voltage)
(From HSDU Int2 Pupil Materials Pack)
42.
a) Explain what is meant by the term potential difference
b ) Describe the difference between the voltage (or potential difference) and the current in a
circuit.
c) Give the name of the unit used to measure voltage or potential difference.
Practice questions on specific heat capacity
(From HSDU Int2 Pupil Materials Pack)
43. 10000 J of energy raises the temperature of 1 kg of liquid by 2 oC. How much energy will be
required to raise the temperature of 4 kg of the liquid by 1 oC?
44. The specific heat capacity of concrete is about 800 Jkg-1 C-1. How much energy is stored
thermally in a storage heater containing 50 kg of concrete when it is heated through 100 oC?
45. 1.344 MJ of energy are used to heat water from 20 oC to 100 oC. Calculate the mass of
water if the specific heat capacity of water is 4200 Jkg-1 oC -1.
46. 9600 J of energy is supplied to 1 kg of methylated spirit in a polystyrene cup.
Calculate the rise in temperature produced.
Take the specific heat capacity of methylated spirit to be 2300 Jkg-1 oC -1.
47. When 2.0 x 104 J of energy is supplied to 4 kg of paraffin at 10 oC in a container the
temperature increases to 14 oC.
a) Calculate the specific heat capacity of the paraffin.
b) Explain why the result in part a) is different from the theoretical value of
2200 Jkg-1 oC -1.
48. If a kettle containing 2 kg of water cools from 40 oC to 25 oC, calculate the energy released
through heating by the water.
49. The temperature of a 0.8 kg metal block is raised from 27 oC to 77 oC when 4200 J of energy
is supplied. Find the specific heat capacity of the metal.
50. The tip of the soldering iron is made of copper with a mass of 30 g. Calculate how much
energy is required to heat up the tip of a soldering iron by 400 oC. (specific heat capacity
of copper = 380 Jkg-1 oC -1)
51. On cold clear nights following hot summer days the temperature in cities is often higher
than in surrounding urban areas. Use your understanding of physics to explain this
phenomenon.
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52. If 200 g of water at 40 oC are mixed with 100 g of water at 10 oC and no energy is lost, what is
the final temperature of the mixture?
(Specific heat capacity of water = 4200 Jkg-1 oC -1)
53. If an immersion heater heats 300 g of water for 2 minutes and the temperature rises by 30 oC,
find the power rating of the heater in watts.
54. A 350 W element is used to boil 300 g of water in a cup. The initial temperature of the water is
20 oC.
a) How long will it take to reach 100 oC?
b) State any assumptions made.
55. Meteors are small pieces of matter made mostly of iron. Few meteors hit the surface of the
Earth because of the Earth’s atmosphere. Assuming all the kinetic energy of the meteor
changes to heat energy in the meteor, if a 0.001 kg meteor travelling at 30000 ms-1 crashes
into the Earth’s atmosphere resulting in a change in temperature of 20000 oC, calculate the
specific heat capacity of the iron.
56. If a copper ball is dropped on a hard surface the ball is deformed, and we can assume all the
kinetic energy is transferred to internal energy in the ball. From what height must
the ball be dropped to raise its temperature by 2 oC?
(Specific heat capacity of copper = 380 Jkg-1 oC -1)
57. An electric shower has a 1.5 kW heating element.
a) How much energy is transferred in five minutes?
b) If the element is used to heat 5 kg of water for 5 minutes, what would be the rise in
temperature? (Specific heat capacity of water = 4200 Jkg-1 oC -1).
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Open Ended Questions for Energy
58. When tending to an open fire, if you turn a log around that has been burning on one side but not the
other, can often make the room feel very warm. Use your knowledge of physics to comment on this.
59. Use your knowledge of physics to comment on why when water pipes freeze there is a danger of them
bursting when the water changes back to a liquid.
60. Some cars are fitted with a system that stores the energy normally lost during braking. Using your
knowledge of physics, estimate the maximum energy that could be stored as a car is decelerated to rest.
Clearly show your working for the calculation and any estimates you have made.
61. Using your knowledge of physics discuss and describe the everyday application of electric charge.
62. Using your knowledge of physics discuss why you think mains electricity is ac rather than dc.
63. What do you think is the most useful type of electricity, ac or dc?
Use your understanding of Physics to support your answer
(Credit is given for justification rather than choice of a.c. or d.c.)
64. A charged polythene rod can be used to bend a narrow stream of water flowing from a tap. Use your
understanding of Physics to explain this effect.
65. A Physics teacher heats up a bowl of soup in a microwave oven.
After two minutes, he finds that the soup and the bowl have not reached the same temperature.
Using your knowledge of physics, explain why this is the case.
66. It is easy to burn your mouth on the contents of a hot apple pie from McDonalds, but still be able to hold
the pie comfortably in your hands.
Using your knowledge of physics, explain why this is possible.
67. A flooring technician was puzzled that slate tiles feel colder than wooden floors but they are both at the
same temperature when measured by thermometer.
Comment on this observation.
68. Using your knowledge of physics design an experiment to demonstrate the difference between
temperature and heat.
Last updated by AD May 2014
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National 5 Section 1 Exam Style Questions for
Energy
69. (Qn 7 Int 2 Physics 2007)
71. (Qn 10 Int 2 Physics 2010)
72. (Qn 11 Int 2 Physics 2010)
70. (Qn 12 Int 2 Physics 2008)
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73. (Qn 9 Int 2 Physics 2011)
74. (Qn 14 Int 2 Physics 2012)
75. (Qn 15 Int 2 Physics 2012)
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National 5 Section 2 Exam Style Questions for
Energy
76. (Qn 12 Credit Physics 2007)
(iv)
The charge stored by the capacitor can be calculated using the formula
Where the area of the capacitor plates, A, is a measure in meters squared. The potential difference, V,
across the plates is measured in Volts and the distance, d, between the plated of the plates of the
capacitor is measured in meters.
The capacitor used in this torch has a plate area of 0.5 m2 and a plate separation of 0.5 mm.
Calculate the charge stored by this capacitor when the there is a potential difference of 1.5 V between
the plated of the capacitor.
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77. (Qn 13 Credit Physics 2007)
78. (Qn 10 Credit Physics 2008)
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79. (Qn 12 Credit Physics 2008)
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(iii)
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80. (Qn 5 Credit Physics 2009)
(ii) An alternative multi-way adapter is in the form of a wound up coil. The instructions on the coiled
adapter advise that the coil of wire should be fully unwound before use. Using your understanding of
physics explain this advice.
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81. (Qn 14 Credit Physics 2009)
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82. (Qn 11 Credit Physics 2010)
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83. (Qn 12 Credit Physics 2010)
Power = 2875 W
(iii) Calculate the charge that flows through the kettle during this time.
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84. (Qn 12 Credit Physics 2011)
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85. (Qn 13 Credit Physics 2012)
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86. (Qn 23 Int 2 Physics 2012)
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87. (Qn 24 Int 2 Physics 2011)
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88. (Qn 23 Int 2 Physics 2010)
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89. (Qn 21 Int 2 Physics 2009)
90. (Qn 24 Int 2 Physics 2008)
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91. (Qn 23 Int 2 Physics 2007)
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Practice questions on generation of electricity
1.
Electricity production system
Wind Turbine
Photo-voltaic cells
Hydroelectric
Advantages
Does not produce carbon
dioxide
Does not produce carbon
dioxide
Does not produce carbon
dioxide
Disadvantages
Electricity not always produced
because it is not always windy
Electricity not always produced
because it is not always sunny
Large areas of land are flooded
to make the reservoir
2.
a) Water is heated by burning a material such as coal oil or gas. The water is heated so much that it
turns into steam. The steam passes along pipes to a turbine where is spins the turbine blades. The
turbine shaft is connected to a generator that produced the electricity.
b) energy in a chemical store, energy in a thermal store, energy in a kinetic store, energy transferred
electrically
Practice questions on electrical power
(From HSDU Int2 Pupil
Materials Pack)
3. The energy transferred per second
4. The number before the W on the rating plate is the power value
5. a) increases cost, b) increases cost, c) increases cost
6. a) 60 J
b) electrical transfer - light transfer – heat transfer – heat store (in environment)
7. a) 115 W
environment)
b) electrical transfer - kinetic store - mechanical transfer – heat store (in
8. a) 18000 J
b) 6000 J
c) 1.92 x 106 J d) 7.2 x 108 J
9. a) 100 W
b) 60 W
c) 3000 W
10. 50 s
11. The percentage of output power in comparison to the input power.
12. Energy is often wasted through heating due to friction.
13. 75%
14. 16 kJ
15. 800 W
Last updated by AD May 2014
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Practice questions on electromagnetism
(From HSDU Int2
Pupil Materials Pack)
16.
17.
6 x 10-6 T
18. Increasing the number of coils of wire around the core, increasing the supply voltage to the wire.
19. By moving a coil through a magnetic field or by moving a magnet near a coil of wire.
20.
21. In sub stations to reduce voltage size, in power stations to increase voltage size, in mobile phone
chargers to decrease voltage size.
22. transformers do not work with d.c. Because they need a changing rather than steady magnetic
field.
Last updated by AD May 2014
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Practice questions on conservation of energy
(From HSDU Int2 Pupil Materials Pack)
23
a) energy in a chemical store, transferred electrically, transferred through heating
b) kettle, toaster, electric fire, hair dryer
2.
a) transfer of energy through heating
b) transfer of energy through heating and kinetic store of energy
c) thermal store of energy
d) kinetic store of energy to thermal and kinetic stores of energy
25. 150 kJ
26. a) 750 J
b) 750 J
27. 300 x mass
28. a) 300 m b) 300J c) 77ms-1
42. 1.6 Nkg-1
43. a)
Use light gate and TSA to determine velocity of vehicle. Pull elastic band back further
each time before releasing car in order to increase the energy transferred to the vehicle during
release. As the elastic band is pulled back further the velocity of the vehicle should increase.
b) E from elastic band = 0.016 J, velocity = 0.4 ms-1
31. a) 40 J
b) 10 kJ
100 J
32. a) 40 kJ b) 500 kg ms-1 down
33.
34.
35.
36.
a) 9 kJ
approx 3 kJ
6 ms-1
22 ms-1
Practice questions on electrical charge
carriers and electric fields
(From HSDU Int2 Pupil Materials Pack)
37.
38.
39.
40.
41.
a) flow of charge per unit time
b) Q =It
c) Q measured in coulombs, I measures in amperes and t measured in seconds
a) 240 C
b) 7.3 A
a) 144 000 C b) 72 000 s or 20 hours c) constant current
a)a.c represents alternating current and means that the electrons change direction.
d.c. Represents direct current and means that the electrons consistently flow in the same
direction.
b) 4.2 A
a)signal generator, mains
b) cell, battery
Last updated by AD May 2014
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Practice questions on potential difference
(voltage)
(From HSDU Int2 Pupil Materials Pack)
42.
a) Energy transferred per coulomb of charge
b) Potential difference is the energy carried by the charge whilst current is the rate of flow of
charge
c) Volt (V)
Practice questions on specific heat capacity
(From HSDU Int2 Pupil Materials Pack)
43. 20000 J
44. 4 x 106 J
45. 4 kg
46. 4.17 oC
47. 2 500 Jkg-1 oC -1
48. 1.26 x 105 J
49. 105 Jkg-1 oC -1
50. 4560 J
51. During the day the builds/road materials absorb energy and increase in temperature. During
night this energy is released into the surroundings keeping the air in the city warmer.
52. 30 oC
53. 315 W
54. a) 288 s
55. 625 Jkg-1 oC -1
56. 76 m
57. a) 4.5 x 105 J b) 21.4 oC
National 5 Section 1 Exam Style Questions for
Energy
69. C (Qn 7 Int 2 Physics 2007)
72. B (Qn 11 Int 2 Physics 2010)
74. D (Qn 14 Int 2 Physics 2012)
70. E (Qn 12 Int 2 Physics 2008)
73. B (Qn 9 Int 2 Physics 2011)
75. D (Qn 15 Int 2 Physics 2012)
71. D (Qn 10 Int 2 Physics 2010)
Last updated by AD May 2014
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National 5 Section 2 Exam Style Questions for
Energy
76. (Qn 12 Credit Physics 2007)
82. (Qn 11 Credit Physics 2010)
Shaking the torch makes the magnet move in
and out of the coils. This causes a changing
magnetic field which induces a voltage.
t = 75s
Q = 1.3 x 10-8 C
Q = 14.4 C
input power = 400W
83. (Qn 12 Credit Physics 2010)
E = 517500 J
m = 1.7 kg
77. (Qn 13 Credit Physics 2007)
E = 600 000J
78. (Qn 10 Credit Physics 2008)
84. (Qn 12 Credit Physics 2011)
h = 90m
E = 300 J
Energy is lost through heating due to friction
P = 5W
79. (Qn 12 Credit Physics 2008)
P = 12.5 W
80. (Qn 5 Credit Physics 2009)
P = 72W
85. (Qn 13 Credit Physics 2012)
81. (Qn 14 Credit Physics 2009)
E = 52500 J
m = 0.33 kg
E = 3.609x109 J
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86. (Qn 23 Int 2 Physics 2012)
89. (Qn 21 Int 2 Physics 2009)
(i) 96.5 J
(ii) 0.5 oC
(iii) less than. Some heat is lost to
surroundings.
a) 10800000 J
b) 8 m/s
c)
i) 120 A
87. (Qn 24 Int 2 Physics 2011)
ii) 1.64 x108 J
a) (i) 12 oC
90. (Qn 24 Int 2 Physics 2008)
(ii) 108,000 J
a) 54000 J
(iii) 4,500 J/kgoC
b) i) 54000J
ii) v = 12 m/s
91. (Qn 23 Int 2 Physics 2007)
c) P = 360 W
i) 3.34x106 J
88. (Qn 23 Int 2 Physics 2010)
ii) t = 1340 s
a) c = 899 J/kgoC
b) t = 18000 s
c) 200 rocks
iii) not all heat energy used to heat water
OR
Heat energy transferred to surroundings
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