Q1. A student investigated the efficiency of a motor using the equipment in Figure 1. Figure 1 He used the motor to lift a weight of 2.5 N a height of 2.0 m. He measured the speed at which the weight was lifted and calculated the efficiency of the energy transfer. He repeated the experiment to gain two sets of data. (a) Give one variable that the student controlled in his investigation. ______________________________________________________________ ___(1) (b) Give two reasons for taking repeat readings in an investigation. 1. ______________________________________________________________ ___ ______________________________________________________________ _____ 2. ______________________________________________________________ ___ ______________________________________________________________ ___(2) (c) Figure 2 shows a graph of the student’s results. Figure 2 Page 1 of 41
Transcript
Q1. A student investigated the efficiency of a motor using the equipment in Figure 1.Figure 1
He used the motor to lift a weight of 2.5 N a height of 2.0 m.He measured the speed at which the weight was lifted and calculated the efficiency of the energy transfer.He repeated the experiment to gain two sets of data.
(a) Give one variable that the student controlled in his investigation.
(b) A student tested four different types of fleece, J, K, L and M, to find which would make the warmest jacket. Each type of fleece was wrapped around a can which was then filled with hot water.The temperature of the water was taken every two minutes for 20 minutes.
The graph shows the student’s results.
(i) In each test, the water cooled faster during the first five minutes than during the last five minutes. Why?
(ii) To be able to compare the results, it was important to use the same volume of water in each test. Give one other quantity that was the same in each test.
(ii) How many protons are in the nucleus of a atom?
__________________(1)
(iii) How many neutrons are in the nucleus of a atom?
__________________(1)
(b) A nucleus can be accelerated in a particle accelerator and directed at a large nucleus. This produces a heavy nucleus that will decay after a short time.This is shown in Figure 1.
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(i) In 1984, nuclei of iron (Fe) were directed at nuclei of lead (Pb). This produced nuclei of hassium (Hs).
Complete the equation for this reaction by writing numbers in the empty boxes.
(3)
(ii) Use the correct answer from the box to complete the sentence.
an electron a proton a neutron
The particle X in part (b)(i) is _________________________________ .(1)
(iii) After acceleration the iron nuclei travel at a steady speed of one-tenth of the speed of light.
The speed of light is 3.00 × 108 m/s.
Calculate the time taken for the iron nuclei to travel a distance of 12 000 m.
(iv) Linear accelerators, in which particles are accelerated in a straight line, are not used for these experiments. Circular particle accelerators are used.
(b) Different electrical wires need to have a cross-sectional area that is suitable for the power output. Figure 2 shows the recommended maximum power input to wires of different cross-sectional areas.
Figure 2
The new electric shower has a power input of 13.8 kW.Determine the minimum diameter of wire that should be used for the new shower.The diameter, d, can be calculated using the equation:
Q12.(a) In the National Grid, very large step-up transformers link power stations to the transmission cables.
A transformer used for this purpose has 800 turns on its primary coil and 12 800 turns on its secondary coil. The p.d. (potential difference) across its primary coil is 25 kV.
Use the equation in the box to calculate the p.d. across its secondary coil.
(b) Nuclear fusion also releases energy.Nuclear fusion happens at very high temperatures. A high temperature is needed to overcome the repulsion force between the nuclei.
(i) Why is there a repulsion force between the nuclei of atoms?
(c) In 1991, scientists produced the first controlled release of energy from an experimental nuclear fusion reactor. This was achieved by fusing the hydrogen isotopes, deuterium and tritium.
Deuterium is naturally occurring and can easily be extracted from seawater. Tritium can be produced from lithium. Lithium is also found in seawater.
The table gives the energy released from 1 kg of fusion fuel and from 1 kg of fission fuel.
Type of fuel Energy released from1 kg of fuel in joules
Fusion fuel 3.4 × 1014
Fission fuel 8.8 × 1013
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(i) Suggest two advantages of the fuel used in a fusion reactor compared with plutonium and the other substances used as fuel in a fission reactor.
(ii) Some scientists think that by the year 2050 a nuclear fusion power station capable of generating electricity on a large scale will have been developed.
Suggest one important consequence of developing nuclear fusion power stations to generate electricity.
Half-life = __________________ years (2) (Total 9 marks)
Q14.(a) Some rocks inside the Earth contain uranium-238, a radioactive isotope of uranium. When an atom of uranium-238 decays, it gives out radiation and changes into a thorium-234 atom.
(i) What type of radiation is emitted when a uranium-238 atom decays?
(ii) Complete the graph to show how the number of nuclei in a sample of uranium-238 will change with time.Initially, there were 100 000 nuclei in the sample.
(2)
(Total 6 marks)
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Mark schemesQ1.
(a) weight (lifted)orheight (lifted)
1(b) any two from:
• calculate a mean• spot anomalies• reduce the effect of random errors
2(c) as speed increases, the efficiency increases
1(but) graph tends towards a constant valueorappears to reach a limit
accept efficiency cannot be greater than 100%1
(d) heating the surroundings1
(e) 0 (%)1
[7]Q2.
(a) (i) radiation1
(ii) traps (small pockets of) air do not accept it’s an insulatordo not accept reduces conduction and / or convectiondo not allow it doesn’t allow heat to escape
1(b) (i) bigger temperature difference (between the water and surroundings)
at the start (than at the end)do not accept water is hotter
1(ii) starting temperature (of the water)
accept thickness of fleecedo not accept same amount of fleecedo not accept thermometer / cando not accept time is the same
1(iii) 18 (°C)
correct answer only1
(iv) M1
smallest temperature drop (after 20 mins)cannot score if M is not chosenaccept it’s the best insulatoraccept smallest loss in heataccept keeps heat / warmth in for longer
1[7]
Q3.(a) most alpha particles pass straight through the atom
1which shows that the atom is mostly empty space
1very few alpha particles are deflected through a large angle
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1which shows the atom contains a nucleus where the mass / charge of the atom is concentrated
1(b) electron may absorb electromagnetic radiation
full credit may be scored for a description of an electron emitting electromagnetic radiation
1(and) move further from the nucleus
1to a higher energy level
1[7]
Q4.(a) (i) (atoms with the) same number of protons
allow same atomic numberor same proton number
1(atoms with) different number of neutrons
allow different mass number1
(ii) 821
(iii) 1241
(b) (i)
1 mark for each correct box3
(ii) (a) neutron1
(iii) 4.0 × 10-4 (s)or0.0004
3.00 × 108 × 0.1 = 12 000 / tgains 1 mark
2(iv) particles need to travel a large distance
1equipment would have to be very long
1with circular paths long distances can be accommodated in a smaller space
1(c) (i) the average time for the number of nuclei to halve
1the time for count rate to halve
1
(ii)
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1 mark if top boxes total = 265and bottom boxes total = 1081 mark for 4 and 2 for alpha
2(d) (i) 3 plotted points
± ½ small square1
best line through points1
(ii) 190−205 (pm)or correct from student’s line
1[20]
Q5.(a) current
1(b) 4.2 = 3.5 × 10–3 × R
1R = 4.2 / 3.5 × 10–3
1R = 1200 (Ω)
an answer of 1200 (Ω) scores 3 marksan answer of 1.2 scores 2 marks
1(c) conversion from minutes to seconds (300 s)
1Q = 0.0035 × (5 × 60)
1Q = 1.05 C
an answer of 1.05 (C) scores 3 marksan answer of 17.5 scores 1 markan answer of 1050 or 0.0175 scores 2 marks
1(d) (potential difference) increases
1(because thermistor) resistance increases
2nd mark dependent on scoring 1st mark1
(e) 1
[10]Q6.
(a) solidparticles vibrate about fixed positions
1closely packed
accept regular1
gasparticles move randomly
accept particles move fasteraccept freely for randomly
1far apart
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1(b) amount of energy required to change the state of a substance from liquid to
gas (vapour)1
unit mass / 1 kgdependent on first marking point
1(c) 41000 or 4.1 × 104 (J)
accept41400 or 4.14 × 104
correct substitution of0.018 × 2.3 × 106 gains 1 mark
2(d) AB
changing state from solid to liquid / melting1
at steady temperaturedependent on first AB mark
1BCtemperature of liquid rises
1until it reaches boiling point
dependent on first BC mark1
[12]Q7.
Level 3 (5–6 marks):A detailed and coherent explanation is provided. The student gives examples that argue a strong case and demonstrate deep knowledge. The student makes logical links between clearly identified, relevant points.Level 2 (3–4 marks):An attempt to link the description of the experiment and the results with differences between the two models. The student gives examples of where the plum pudding model does not explain observations. The logic used may not be clear.Level 1 (1–2 marks):Simple statements are made that the nuclear model is a better model. The response may fail to make logical links between the points raised.0 marks:No relevant content.Indicative content• alpha particle scattering experiment• alpha particles directed at gold foil• most alpha particles pass straight through• (so) most of atom is empty space• a few alpha particles deflected through large angles• (so) mass is concentrated at centre of atom• (and) nucleus is (positively) charged• plum pudding model has mass spread throughout atom• plum pudding model has charge spread throughout atom
[6]Q8.
(a) Student A’s measurements had a higher resolution1
Student B was more likely to misread the temperature1
(b) a random error1
(c) 8.4 °C
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1(d) 740 (seconds)
allow answers in the range 730 – 7801
(e) 0.40 × 199 0001
79 600 (J)1
accept 79 600 (J) with no working shown for 2 marks(f) stearic acid has a higher temperature than the surroundings
accept stearic acid is hotter than the surroundings1
temperature will decrease until stearic acid is the same as the room temperature / surroundings
1[9]
Q9.(a) (because the) potential of the live wire is 230 V
1(and the) potential of the electrician is 0 V
1(so there is a) large potential difference between live wire and electrician
1charge / current passes through his body
allow voltage for potential difference1
(b) diameter between 3.50 and 3.55 (mm)allow correct use of value of cross-sectional area of 9.5 to 9.9 (mm2) with no final answer given for 1 mark
2(c) 18000 = I × 300
1I = 18000 / 300 = 60
113 800 = (602) × R
1R = 13 800 / 602
13.83 (Ω)
1allow 3.83(Ω) with no working shown for 5 marksanswer may also be correctly calculated using P = IV and V = IR if 230 V is used.
[11]Q10.
(a) Level 2: Relevant reasons are identified, given in detail and logically linked to form a clear account. 3-4
Level 1: Relevant reasons are identified, and there are attempts at logically linking. The resulting account is not fully clear. 1-2
No relevant content 0Indicative contentnuclear• no carbon dioxide released (when generating electricity) or
doesn’t release greenhouse gases• reliable• high energy density• power stations already built• other power stations being built
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wind• no carbon dioxide released (when generating electricity) or
doesn’t release greenhouse gases• renewable energy resource• no fuel cost
4(b) wind power is unreliable
1(so) will be unable to meet demand when wind speed is loworwhen there is no windorunable to maintain base load at all times
1(c) electricity generation will need to increase (to meet higher
(b) (i) any one from:do not accept any response in terms of heat insulation, safety or electric shock
• (so that there is) no short circuit• (so that the) current goes around the coil
do not accept electricity for current• (so that the) current does not enter the core
1(ii) (easily) magnetised (and demagnetised)
accept ‘(it’s) magnetic’ do not accept ‘because it’s a conductor’
1(iii) alternating current in the primary (coil)
1produces a changing magnetic field (in the core)
1this induces an (alternating) potential difference across the secondary (coil)
1(c) any two from:
• if the (local) power station breaks down / fails / demand / load exceeds supply
• electricity / power can be switched from elsewhere in the system / from other power station(s)
• electricity can be generated in places remote from customers• (in total) fewer power stations are needed• power available in rural / remote areas• National Grid allows for (better) control of supply and demand
2[9]
Q13.(a) (i) splitting of a(n atomic) nucleus
do not accept splitting an atom1
(ii) Neutron1
(b) (i) nuclei have the same chargeornuclei are positive
accept protons have the same charge1
(ii) (main sequence) staraccept Sun or any correctly named staraccept red (super) giant
1
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(c) (i) any two from:• easy to obtain / extract• available in (very) large amounts• releases more energy (per kg)
do not accept figures only• produces little / no radioactive waste.
naturally occurring is insufficientseawater is renewable is insufficientless cost is insufficient
2(ii) any one from:
• makes another source of energy available• increases supply of electricity• able to meet global demand• less environmental damage• reduces amount of other fuels used.
accept any sensible suggestionaccept a specific exampleaccept a specific example
1(d) 12
allow 1 mark for obtaining 3 half-lives2
[9]Q14.
(a) (i) alpha (particle)1
(ii) (unstable) nucleus accept (unstable) nucleido not accept middledo not accept helium nucleus
1(iii) same number of protons
accept same number of electronsaccept same atomic / proton numberaccept they both have 92 protonssame number of neutrons negates answer
1(b) (i) 4500 million years
do not accept 4500 years1
(ii) curve starting at 100 000 with a correct general shape1
passing through (4500, 50 000) and (9000, 25 000)allow 1 mark for points plottedorline passing through (4500, 50 000) and (9000, 25 000)
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