Current, Potential difference and resistance

Transcription

1 Current, Potential difference and resistance Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Current, potential difference and resistance Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 60 minutes Score: /59 Percentage: /00 Page

2 M. (a) current that is always in the same direction (b) total resistance = 30 (Ω) V = (V) allow (V) with no working shown for 3 marks an answer of 8 (V) or 4 (V) gains marks only (c) P = 0.4 = (W) allow 5 (W) with no working shown for marks allow 4.8 (W) with no working shown for mark [6] Page

3 M. (a) (i) or their (a)(i) x 0.3 correctly calculated allow mark for correct substitution, ie 0.3 x 5/their (a)(i), provided no subsequent step decrease (b) Y accept any correct indication reason only scores if Y is chosen accept voltage for p.d. (only one that) shows a direct current / p.d. or a battery / cell gives a direct current accept both X and Z are a.c. or a battery/cell gives a constant current/p.d. accept it s a constant current/p.d. it is not changing is insufficient [6] Page 3

4 M3. (a) (i) 50 (Hz) 760 (W) (b) allow mark for correct substitution, ie 400/00 or allow mark for 760/30 provided no subsequent step shown amps (c) the charge is directly proportional to the time switched on for accept for mark the longer time (to boil), the greater amount of charge or positive correlation or they are proportional [7] Page 4

5 M4. (a) 5(Ω) (b) (i) (V) allow mark for showing a correct method, ie 6 / 3 equal to [4] Page 5

6 M5.(a) allow mark for each correct line if more than one line is drawn from any symbol then all of those lines are wrong 3 (b) (i) half 3(V) (iii) V (c) (i) potential difference / voltage of the power supply accept the power supply accept the voltage / volts accept number of cells / batteries accept (same) cells / batteries do not accept same ammeter / switch / wires bar drawn height.(00)a ignore width of bar allow mark for bar shorter than 3 rd bar (iii) as the number of resistors increases the current decreases [0] Page 6

7 M6.(a) Save My Exams! The Home of Revision battery, lamp and ammeter connected in series with variable resistor voltmeter in parallel with (filament) lamp (b) Level (3 4 marks): A detailed and coherent description of a plan covering all the major steps is provided. The steps are set out in a logical manner that could be followed by another person to obtain valid results. Level ( marks): Simple statements relating to relevant apparatus or steps are made but they may not be in a logical order. The plan would not allow another person to obtain valid results. 0 marks: No relevant content Indicative content ammeter used to measure current voltmeter used to measure potential difference resistance of variable resistor altered to change current in circuit or change potential difference (across filament lamp) resistance (of filament lamp) calculated or R=V / I statement resistance calculated for a large enough range of different currents that would allow a valid conclusion about the relationship to be made 4 (c) (as current increases) resistance increases (at an increasing rate) (d) any value between 6.3 and 6.9 (Ω) (e) A: Filament lamp B: Resistor at constant temperature Page 7

8 C: Diode [] Page 8

9 M7.(a) (i) any six from: switch on read both ammeter and voltmeter allow read the meters adjust variable resistor to change the current take further readings draw graph (of) V against I allow take mean R = V / I allow take the gradient of the graph 6 resistor would get hot if current left on so its resistance would increase (iii) (V) gains mark (iv) 5 (Ω) 6 is nearer to that value than any other (b) if current is above 5 A / value of fuse fuse melts allow blows / breaks do not accept exploded Page 9

10 breaks circuit [5] Page 0

11 Current, potential difference and resistance Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Current, Potential difference and resistance Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 55 minutes Score: /55 Percentage: /00 Page

12 M. (a) V = (V) (b) R = / 0.0 total resistance = 0 (Ω) R = 0 05 = 5 (Ω) (c) (total) resistance decreases (so) current increases [7] Page

13 M. (a) (i) also double increases is insufficient variable resistor accept rheostat / potentiometer (b) (i) the data / results / variables are continuous accept data / results / variables are not categoric / discrete misreading the ammeter do not accept misreading the meter / results do not accept misreading the ammeter and / or voltmeter reading / human error is insufficient (iii) straight line from the origin drawn passing close / through points at V, 5 V, 6 V and ignoring anomalous point do not accept line drawn dot-to-dot (iv) yes mark is for the reason supports predictionor(straight) line passes through the origin accept a mathematical argument, eg when p.d. went from to 4 the current went from 0.3 to 0.6 it s directly proportional is insufficient [6] Page 3

14 M3. (a) decreases (b) a filament bulb allow bulb an LED (c) Marks awarded for this answer will be determined by the Quality of Communication (QoC) as well as the standard of the scientific response. 0 marks No relevant content. Level ( marks) There is a basic description of the method. This is incomplete and would not lead to any useful results. Level (3 4 marks) There is a description of the method which is almost complete with a few minor omissions and would lead to some results. Level 3 (5 6 marks) There is a detailed description of the method which would lead to valid results. To gain full marks an answer including graph, or another appropriate representation of results, must be given. examples of the physics points made in the response: read V and I read temperature apply heat allow hot water to cool read V and I at least one other temperature determine R from V / I range of temperatures above 50 C extra detail: use thermometer to read temperature at regular intervals of temperature remove source of heat and stir before taking readings details of attaining 0 C or 00 C last reading taken while boiling graph of R against T Page 4

15 at least 3 different temperatures 6 (d) (i) Q (80, 3.8) (iii) any one from: measurement of V too small measurement of I too big incorrect calculation of R thermometer misread allow misread meter ignore any references to an error that is systematic (iv) any two from: not portable allow requires a lot of equipment allow takes time to set up needs an electrical supply cannot be read directly accept it is more difficult to read compared to liquid-in-glass [4] Page 5

16 M4. (a) (i) ammeter symbol correct and drawn in series accept do not accept lower case a voltmeter symbol correct and drawn in parallel with the material do not accept adjust / use the variable resistor accept change the resistance orchange the number of cells accept battery for cell accept change the pd / accept change the voltage accept increase / decrease for change (b) (i) 37.5 (Ω) accept answer between 36 and 39 inclusive 5.6(5) or their (b)(i) 0.5 allow mark for correct substitution ie 37.5 or their (b)(i) 0.5 provided no subsequent step shown (c) (i) the thicker the putty the lower the resistance answer must be comparativeaccept the converse any one from: measuring length incorrectly accept may be different length Page 6

17 measuring current incorrectly do not accept different currents measuring voltage incorrectly do not accept different voltage ammeter / voltmeter incorrectly calibrated thickness of putty not uniform do not accept pieces of putty not the same unless qualified meter has a zero error do not accept systematic / random error accept any sensible source of error eg putty at different temperatures do not accept human error without an explanation do not accept amount of putty not same [8] Page 7

18 M5. (a) (i) to obtain a range of p.d. values accept increase / decrease current / p.d. / voltage / resistance accept to change / control the current / p.d. / voltage / resistance to provide resistance is insufficient a variable resistor is insufficient do not accept electricity for current temperature of the bulb increases accept bulb gets hot(ter) accept answers correctly expressed in terms of collisions between (free) electrons and ions / atoms bulb gets brighter is insufficient (iii) 36 allow mark for correct substitution, ie 3 provided no subsequent step shown watt(s) / W accept joules per second / J/s do not accept w (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a best-fit approach to the marking. 0 marksno relevant content. Level (- marks)there is a basic comparison of either a cost aspect or an energy efficiency aspect. Level (3-4 marks)there is a clear comparison of either the cost aspect or Page 8

19 energy efficiency aspectora basic comparison of both cost and energy efficiency aspects. Level 3 (5-6 marks)there is a detailed comparison of both the cost aspect and the energy efficiency aspect. For full marks the comparisons made should support a conclusion as to which type of bulb is preferable. Examples of the points made in the response: cost halogen are cheaper to buy simply giving cost figures is insufficient 6 halogen lamps cost the same as one LED LEDs last longer need to buy 8 / more halogen lamps to last the same time as one LED 8 halogens cost 35.0 costs more to run a halogen than LED LED has lower maintenance cost (where many used, eg large departmental store lighting) energy efficiency LED works using a smaller current LED wastes less energy LEDs are more efficient LED is % more energy efficient LED produces less heat LED requires smaller input (power) for same output (power) 6 [] Page 9

20 M6. (a) (i) live react faster (iii) live and neutral (b) (i) ammeter to measure current accept to measure amps plus any one from: variable resistor () to vary current () accept variable power supply accept change or control switch () to stop apparatus getting hot / protect battery or to reset equipment () fuse () to break circuit if current is too big () any two from: use smaller mass(es) move mass closer to pivot reduce gap between coil and rocker more turns (on coil)coil / loop iron core in coil accept use smaller weight(s) Page 0 [9]

21 Current, potential difference and resistance Mark scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Current, potential difference and resistance Difficulty Level Gold Level Booklet Mark Scheme Time Allowed: 5 minutes Score: /49 Percentage: /00 Page

22 M.(a) battery in series with bulb and ammeter voltmeter in parallel with bulb variable resistor or variable power pack or potentiometer (b) A is brighter because it has a higher current (than lamp B at any p.d.) (therefore A has a) higher power output (than bulb B) accept higher energy output per second (c) lower current (than lamp A) for the same potential difference accept answer in terms of R = V / I lower gradient (than lamp A) Page

23 (d) 0 Volts allow a range from 0 V up to any value between and V. (for an ohmic conductor) current is directly proportional to potential difference allow lines (of best fit) are straight and pass through the origin (so) resistance is constant [0] Page 3

24 M. (a) (i) 360 allow mark for correct substitution, ie 9 = 0.05 R (iii) sketch graph of correct shape, ie (iv) An automatic circuit to switch a heating system on and off. (b) so ammeter reduces / affects current as little as possible accept so does not reduce / change the current (it is measuring) accurate reading is insufficient not change the resistance is insufficient (c) gives a common understanding accept is easier to share results accept can compare results do not need to be converted is insufficient prevent errors is insufficient Page 4

25 (d) replace Bunsen (and water) with a lamp accept any way of changing light level replace thermometer with light sensor accept any way of measuring a change in light level datalogger alone is insufficient [9] Page 5

26 M3. (a) 35 an answer with more than sig figs that rounds to 35 gains marks allow marks for correct method, ie allow mark for I = 6.5 (A) or R = an answer 8.8 gains marks an answer with more than sig figs that rounds to 8.8 gains mark 3 (b) (maximum) current exceeds maximum safe current for a.5 mm wire accept power exceeds maximum safe power for a.5 mm wire or(maximum) current exceeds 0 (A) (maximum) current = 6 (A) is insufficient a.5 mm wire would overheat / melt accept socket for wire do not accept plug for wire (c) a.c. is constantly changing direction accept a.c. flows in two directions accept a.c. changes direction a.c. travels in different directions is insufficient d.c. flows in one direction only [7] Page 6

27 M4. (a) attempt to draw four cells in series correct circuit symbols circuit symbol should show a long line and a short line, correctly joined together example of correct circuit symbol: (b) (i) 6 (V) allow mark for correct substitution, ie V = 3 scores mark provided no subsequent step (V) ecf from part (b)(i) 8 6 or 8 their part (b)(i) scores mark (iii) 9 (Ω) ecf from part (b) correctly calculated 3 + their part (b) / or 8 / scores mark provided no subsequent step (c) (i) need a.c. battery is d.c. Page 7

28 3 (A) allow mark for correct substitution, ie 8 = I s scores mark [] Page 8

29 M5. (a) (because the) potential of the live wire is 30 V (and the) potential of the electrician is 0 V (so there is a) large potential difference between live wire and electrician charge / current passes through his body allow voltage for potential difference (b) diameter between 3.50 and 3.55 (mm) allow correct use of value of cross-sectional area of 9.5 to 9.9 (mm ) with no final answer given for mark (c) 8000 = I 300 I = 8000 / 300 = = (60 ) R R = / (Ω) Page 9

30 allow 3.83(Ω) with no working shown for 5 marks answer may also be correctly calculated using P = IV and V = IR if 30 V is used. [] Page 0

31 Domestic uses and safety Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Domestic uses and safety Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 60 minutes Score: /58 Percentage: /00 Page

32 M. (a) any two from: (b) (c) (d) nuclear oil (natural) gas 4 (hours) a system of cables and transformers The power output of wind turbines is unpredictable (e) 500 / (wind turbines) allow 500 with no working shown for marks (f) Most energy resources have negative environmental effects. [8] Page

33 M. (a) iron hairdryer kettle answers can be in any order (b) (i) Y bar drawn with any height greater than Y ignore width of bar (c) (bigger volume) takes more time (to boil) accept explanation using data from graph (so) more energy transferred do not accept electricity for energy (and) this costs more money ignore reference to cost of water wasting more money because heating more water than needed is insufficient [8] Page 3

34 M3.(a) Save My Exams! The Home of Revision there is a magnetic field (around the magnet) (this magnetic field) changes / moves and cuts through coil accept links with coil so a p.d. induced across coil the coil forms a complete circuit so a current (is induced) (b) ammeter reading does not change must be in this order accept ammeter has a small reading / shows a current zero greater than before accept a large(r) reading same as originally but in the opposite direction accept a small reading in the opposite direction Page 4

35 (c) 0.30 allow mark for correct substitution, ie 0.05 = Q / 6 C / coulomb allow A s [3] Page 5

36 M4.(a) (i) any six from: switch on read both ammeter and voltmeter allow read the meters adjust variable resistor to change the current take further readings draw graph (of) V against I allow take mean R = V / I allow take the gradient of the graph 6 resistor would get hot if current left on so its resistance would increase (iii) (V) gains mark (iv) 5 (Ω) 6 is nearer to that value than any other (b) if current is above 5 A / value of fuse fuse melts allow blows / breaks do not accept exploded Page 6

37 breaks circuit [5] Page 7

38 M5. (a) he may receive an electric shock or he may be electrocuted if he touches the live wire (b) = I 30 I = / (60) (A) 46 (c) cost is higher allow 46 (A) with no working shown for 4 marks more energy is used (per second) [8] Page 8

39 M6.(a) Save My Exams! The Home of Revision current that is always in the same direction (b) total resistance = 30 (Ω) V = (V) allow (V) with no working shown for 3 marks an answer of 8 (V) or 4 (V) gains marks only (c) P = 0.4 = (W) allow 5 (W) with no working shown for marks allow 4.8 (W) with no working shown for mark [6] Page 9

40 Domestic uses and safety Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Domestic uses and safety Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 57 minutes Score: /57 Percentage: /00 Page

41 M. (a) (i) 50 transferred to the surroundings by heating reference to sound negates mark (iii) / 600 gains mark accept 75% for marks maximum of mark awarded if a unit is given (iv) 0 (s) correct answer with or without working gains marks correct substitution of 600 / 30 gains mark (b) (i) to avoid bias use less power and last longer LED costs 6, 40 filament bulbs cost 80 or filament costs (5 times) more in energy consumption (iii) any one from: availability of bulbs Page

42 colour output temperature of bulb surface [0] Page 3

43 M. (a) brown (b) outside / case is plastic / an insulator accept is double insulated accept non-conductor for plastic do not accept it / hairdryer is plastic (c) (i) () S and no other () S and S 3 both required, either order S must be ON (for either heater to work) do not accept reference to fan switch S switches the fan on (d) 495 allow mark for correct substitution ie, watt(s) or W an answer of.495 kw gains 3 marks although the unit is an independent mark for full credit the unit and numerical value must be consistent accept joules per second or J/s Page 4 [9]

44 M3. (a) (i) to obtain a range of p.d. values accept increase / decrease current / p.d. / voltage / resistance accept to change / control the current / p.d. / voltage / resistance to provide resistance is insufficient a variable resistor is insufficient do not accept electricity for current temperature of the bulb increases accept bulb gets hot(ter) accept answers correctly expressed in terms of collisions between (free) electrons and ions / atoms bulb gets brighter is insufficient (iii) 36 allow mark for correct substitution, ie 3 provided no subsequent step shown watt(s) / W accept joules per second / J/s do not accept w (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a best-fit approach to the marking. 0 marksno relevant content. Level (- marks)there is a basic comparison of either a cost aspect or an energy efficiency aspect. Page 5

45 Level (3-4 marks)there is a clear comparison of either the cost aspect or energy efficiency aspectora basic comparison of both cost and energy efficiency aspects. Level 3 (5-6 marks)there is a detailed comparison of both the cost aspect and the energy efficiency aspect. For full marks the comparisons made should support a conclusion as to which type of bulb is preferable. Examples of the points made in the response: cost halogen are cheaper to buy simply giving cost figures is insufficient 6 halogen lamps cost the same as one LED LEDs last longer need to buy 8 / more halogen lamps to last the same time as one LED 8 halogens cost 35.0 costs more to run a halogen than LED LED has lower maintenance cost (where many used, eg large departmental store lighting) energy efficiency LED works using a smaller current LED wastes less energy LEDs are more efficient LED is % more energy efficient LED produces less heat LED requires smaller input (power) for same output (power) 6 [] Page 6

46 M4. (a) (i) live react faster (iii) live and neutral (b) (i) ammeter to measure current accept to measure amps plus any one from: variable resistor () to vary current () accept variable power supply accept change or control switch () to stop apparatus getting hot / protect battery or to reset equipment () fuse () to break circuit if current is too big () any two from: use smaller mass(es) move mass closer to pivot reduce gap between coil and rocker more turns (on coil)coil / loop iron core in coil Page 7

47 accept use smaller weight(s) [9] Page 8

48 M5. (a) (black) is a good absorber of (infrared) radiation (b) (i) amount of energy required to change (the state of a substance) from solid to liquid (with no change in temperature) melt is insufficient unit mass / kg (J) accept 5 x 0 6 allow mark for correct substitution ie E = (c) (i) mass of ice allow volume / weight / amount / quantity of ice to distribute the salt throughout the ice to keep all the ice at the same temperature (iii) melting point decreases as the mass of salt is increased allow concentration for mass accept negative correlation do not accept inversely proportional (d) (J) accept 60 KJ allow marks for correct substitution ie E = Page 9

49 allow marks for an answer of 000 or 60 allow mark for correct substitution ie E = or allow mark for an answer of 3 (e) Marks awarded for this answer will be determined by the Quality of Communication (QC) as well as the standard of the scientific response. Examiners should also apply a best-fit approach to the marking. 0 marks No relevant content Level ( marks) There is an attempt at a description of some advantages or disadvantages. Level (3 4 marks) There is a basic description of some advantages and / or disadvantages for some of the methods Level 3 (5 6 marks) There is a clear description of the advantages and disadvantages of all the methods. examples of the points made in the response energy storage advantages: extra information no fuel costs no environmental effects disadvantages: expensive to set up and maintain need to dig deep under road dependent on (summer) weather digging up earth and disrupting habitats salt spreading advantages: easily available cheap disadvantages: can damage trees / plants / drinking water / cars needs to be cleaned away Page 0

50 undersoil heating advantages: not dependent on weather can be switched on and off disadvantages: costly bad for environment 6 [8] Page

51 Domestic uses and safety Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Domestic uses and safety Difficulty Level Gold Level Booklet Mark Scheme Time Allowed: 5 minutes Score: /5 Percentage: /00 Page

52 M. (a) (because the) potential of the live wire is 30 V (and the) potential of the electrician is 0 V (so there is a) large potential difference between live wire and electrician charge / current passes through his body allow voltage for potential difference (b) diameter between 3.50 and 3.55 (mm) allow correct use of value of cross-sectional area of 9.5 to 9.9 (mm ) with no final answer given for mark (c) 8000 = I 300 I = 8000 / 300 = = (60 ) R R = / (Ω) Page

53 allow 3.83(Ω) with no working shown for 5 marks answer may also be correctly calculated using P = IV and V = IR if 30 V is used. [] Page 3

54 M. (a) 35 an answer with more than sig figs that rounds to 35 gains marks allow marks for correct method, ie allow mark for I = 6.5 (A) or R = an answer 8.8 gains marks an answer with more than sig figs that rounds to 8.8 gains mark 3 (b) (maximum) current exceeds maximum safe current for a.5 mm wire accept power exceeds maximum safe power for a.5 mm wire or(maximum) current exceeds 0 (A) (maximum) current = 6 (A) is insufficient a.5 mm wire would overheat / melt accept socket for wire do not accept plug for wire (c) a.c. is constantly changing direction accept a.c. flows in two directions accept a.c. changes direction a.c. travels in different directions is insufficient d.c. flows in one direction only [7] Page 4

55 M3. (a) water heated by radiation (from the Sun) accept IR / energy for radiation water used to heat buildings / provide hot water allow for mark heat from the Sun heats water if no other marks given references to photovoltaic cells / electricity scores 0 marks (b) (minutes) = gains mark calculation of time of 0 (seconds) scores marks 3 (c) (i) 50 (kwh) 60(.00) or 6000 (p) an answer of 6000 gains mark allow mark for (0) allow ecf from (c)(i) (iii) 5 (years) an answer of 6000 / 40 or 6000 / their (c) 4 gains marks an answer of 6000 / 60 or 6000 / their (c) gains mark, ignore any other multiplier of (c) 3 Page 5

56 (iv) any one from: will get 40 per year accept value consistent with calculated value in (c)(iii) amount of light is constant throughout the year price per unit stays the same condition of cells does not deteriorate (d) any one from: angle of tilt of cells cloud cover season / shade by trees amount of dirt [3] Page 6

57 M4. (a) attempt to draw four cells in series correct circuit symbols circuit symbol should show a long line and a short line, correctly joined together example of correct circuit symbol: (b) (i) 6 (V) allow mark for correct substitution, ie V = 3 scores mark provided no subsequent step (V) ecf from part (b)(i) 8 6 or 8 their part (b)(i) scores mark (iii) 9 (Ω) ecf from part (b) correctly calculated 3 + their part (b) / or 8 / scores mark provided no subsequent step (c) (i) need a.c. Page 7

58 battery is d.c. 3 (A) allow mark for correct substitution, ie 8 = I s scores mark [] Page 8

59 M5. (a) (i) generator alternating current (iii) voltmeter / CRO / oscilloscope / cathode ray oscilloscope (b) (i) time peaks and troughs in opposite directions amplitude remains constant dependent on first marking point (c) any two from: increase speed of coil strengthen magnetic field increase area of coil do not accept larger [8] Page 9

60 Energy transfers Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Energy Transfers Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 59 minutes Score: /58 Percentage: /00 Page

61 M. (a) current that is always in the same direction (b) total resistance = 30 (Ω) V = (V) allow (V) with no working shown for 3 marks an answer of 8 (V) or 4 (V) gains marks only (c) P = 0.4 = (W) allow 5 (W) with no working shown for marks allow 4.8 (W) with no working shown for mark [6] Page

62 M. (a) (i) A bar drawn with correct height ignore width of bar (b) (i) E = P t.4 allow mark for correct substitution ie. provided no subsequent step shown 36 or their (b)(i) 5 correctly calculated or their (b)(i) 0.5 correctly calculated with an answer given in allow mark for correct substitution ie.4 5 or their (b)(i) 5 allow mark for correct substitution provided no subsequent step shown an answer 0.36 gains both marks [6] Page 3

63 M3. (a) fan drill washing machine four circled including correct three scores mark five circled scores zero (b) Appliances only transfer part of the energy usefully The energy transferred by appliances makes the surroundings warmer [5] Page 4

64 M4. (a) (i) temperature (increase) and time switched on are directly proportional accept the idea of equal increases in time giving equal increases in temperature answers such as: as time increases, temperature increases positive correlation linear relationship temperature and time are proportional score mark any one from: it refers to the metal block energy transfer (from the block) to the surroundings accept lost for transfer accept air for surroundings (some) energy used to warm the heater / thermometer (itself) accept takes time for heater to warm up (metal) block is not insulated (iii) allow mark for correct substitution, ie provided no subsequent step shown (b) lead reason only scores if lead is chosen needs least energy to raise temperature by C accept needs less energy to heat it (by the same amount) lowest specific heat capacity is insufficient [7] Page 5

65 M5. (a) (i) TV hairdryer and sandwich toaster both required either order but no others (b) (i). allow mark for correct substitution ie provided that no subsequent step is shown 8 accept 0.8 for both marks or their (b)(i) 5 correctly calculated an answer 0.8 scores mark allow mark for correct substitution ie. or their (b)(i) 5 provided that no subsequent step is shown [6] Page 6

66 M6. (a) 6.50 allow mark for correct substitution ie 0 5 an answer of 650 gains both marks an answer of gains both marks allow mark for 9 5 (b) 9 allow mark for correctly using the reading ie accept for both marks [4] Page 7

67 M7. (a) iron hairdryer kettle answers can be in any order (b) (i) Y bar drawn with any height greater than Y ignore width of bar (c) (bigger volume) takes more time (to boil) accept explanation using data from graph (so) more energy transferred do not accept electricity for energy (and) this costs more money ignore reference to cost of water wasting more money because heating more water than needed is insufficient [8] Page 8

68 M8. (a) solid (b) decreased correct order only decreased increased (c) (i) A reason only scores if A chosen uses least / less energy (in year) a comparison is required accept uses least power accept uses least kwh greater the volume the greater the energy it uses (in year) (iii) a very small number sampled accept only tested 3 accept insufficient evidence / data allow not all fridges have the same efficiency or a correct description implying different efficiencies only tested each fridge once is insufficient there are lots of different makes is insufficient [8] Page 9

69 M9. (a) he may receive an electric shock or he may be electrocuted if he touches the live wire (b) = I 30 I = / (60) (A) 46 (c) cost is higher allow 46 (A) with no working shown for 4 marks more energy is used (per second) [8] Page 0

70 Energy transfers Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Energy transfers Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 56 minutes Score: /56 Percentage: /00 Page

71 M. (a) (i) kinetic do not accept movement thermal sound accept heat for thermal do not accept noise for sound both answers required in either order (b) transferred to surroundings / surrounding molecules / atmosphere it escapes is insufficient orbecomes dissipated / spread out accept warms the surroundings accept degraded / diluted accept a correct description for surroundings eg to the washing machine do not accept transformed into heat on its own (c) (i) 3 (.0 p) allow mark for correct substitution of correct values ie 0. x 5 allow mark for calculating cost at 40 C (6.5p) or cost at 30 C (3.5p) any two from: less electricity needed ignore answers in terms of the washing machine releasing less energy an answer in terms of the washing machine releasing CO negates mark do not accept less energy is produced fewer power stations needed Page

72 less fuel is burned accept a correctly named fuel do not accept less fuel is needed [7] Page 3

73 M. (a) (i) food processor hairdryer both required and no other either order TV Table lamp Food processor all required and no other any order (b) any two from: transfers / requires / uses more energy / power accept more electricity used accept higher power more electricity needs to be generated more (fossil) fuels (likely) to be burnt accept a named fossil fuel (c) (i) precise this answer only any three from: can look for trends / patterns help reduce energy use / consumption reduce bills accept save money identify appliances which use a lot of energy replace appliances with more efficient ones see effect of leaving appliances on (standby) Page 4

74 to monitor usage is insufficient answers in terms of environment are insufficient 3 [8] Page 5

75 M3. (a) E = P t 9 (p) an answer 0.9 gains 3 marks an answer 0.9 gains marks allow marks for energy transferred = 8. (kwh) or substitution into equations combined, ie allow mark for correct substitution into E = P t, ie E =.6 7 or allow mark for multiplying and correctly calculating an incorrect energy transfer value by 5 3 (b) answers should be in terms of supply exceeding demand accept there is a surplus / excess of electricity (at night) (c) reduce (rate of) energy transfer (from ceramic bricks) accept heat for energy do not accept no energy / heat escapes do not accept answers in terms of lost / losing heat if this implies heat is wasted energy so keeping the (ceramic) bricks hot for longer accept increase time that energy is transferred to the room accept keep room warm for longer or to stop the casing getting too hot accept so you do not get burnt (on the casing) (d) E = m c θ 0 allow mark for correct substitution ie = m [8] Page 6

76 M4. (a) (i) conduction convection correct order only to keep the ceramic bricks hot for a longer time (b) (i) E = P t 8. allow mark for correct substitution ie.6 7 provided that no subsequent step is shown 9 (p) or their (b)(i) 5 correctly calculated accept 0.9 do not accept 0.9 without sign (c) E = m c θ allow mark for correct substitution ie provided that no subsequent step is shown answers 50 kj or.5 MJ gain both marks [8] Page 7

77 M5. (a) advantage any one from: produce no / little greenhouse gases / carbon dioxide allow produces no / little polluting gases allow doesn t contribute to global warming / climate change allow produce no acid rain / sulphur dioxide reference to atmospheric pollution is insufficient produce no harmful gases is insufficient high(er) energy density in fuel accept one nuclear power station produces as much power as several gas power stations nuclear power stations can supply a lot of or more energy is insufficient long(er) operating life allow saves using reserves of fossil fuels or gas disadvantage any one from: produce (long term) radioactive waste accept waste is toxic accept nuclear for radioactive accidents at nuclear power stations may have far reaching or long term consequences high(er) decommissioning costs accept high(er) building costs long(er) start up time (b) (i) 000 (kwh) allow mark for correct substitution eg or or an answer of scores mark Page 8

78 any idea of unreliability, eg wind is unreliable reference to weather alone is insufficient shut down if wind too strong / weak wind is variable (c) any one from: cannot be seen no hazard to (low flying) aircraft / helicopters unlikely to be or not damaged / affected by (severe) weather unlikely to be damaged is insufficient (normally) no / reduced shock hazard safer is insufficient less maintenance is insufficient installed in urban areas is insufficient [6] Page 9

79 M6. (a) water moves (from a higher level to a lower level) transferring GPE to KE rotating a turbine to turn a generator accept driving or turning or spinning for rotating moving is insufficient transferring KE to electrical energy transferring GPE to electrical energy gains mark of the marks available for energy transfers (b) (TVs in stand-by) use electricity accept power / energy generating electricity (from fossil fuels) produces CO accept greenhouse gas accept sulfur dioxide (CO ) contributes to global warming accept climate change for global warming accept greenhouse effect if CO given accept acid rain if linked to sulfur dioxide (c) a factor other than scientific is given, eg economic, political or legal personal choice is insufficient [8] Page 0

80 M7. (a) (i) to obtain a range of p.d. values accept increase / decrease current / p.d. / voltage / resistance accept to change / control the current / p.d. / voltage / resistance to provide resistance is insufficient a variable resistor is insufficient do not accept electricity for current temperature of the bulb increases accept bulb gets hot(ter) accept answers correctly expressed in terms of collisions between (free) electrons and ions / atoms bulb gets brighter is insufficient (iii) 36 allow mark for correct substitution, ie 3 provided no subsequent step shown watt(s) / W accept joules per second / J/s do not accept w (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a best-fit approach to the marking. 0 marksno relevant content. Level (- marks)there is a basic comparison of either a cost aspect or an energy efficiency aspect. Page

81 Level (3-4 marks)there is a clear comparison of either the cost aspect or energy efficiency aspectora basic comparison of both cost and energy efficiency aspects. Level 3 (5-6 marks)there is a detailed comparison of both the cost aspect and the energy efficiency aspect. For full marks the comparisons made should support a conclusion as to which type of bulb is preferable. Examples of the points made in the response: cost halogen are cheaper to buy simply giving cost figures is insufficient 6 halogen lamps cost the same as one LED LEDs last longer need to buy 8 / more halogen lamps to last the same time as one LED 8 halogens cost 35.0 costs more to run a halogen than LED LED has lower maintenance cost (where many used, eg large departmental store lighting) energy efficiency LED works using a smaller current LED wastes less energy LEDs are more efficient LED is % more energy efficient LED produces less heat LED requires smaller input (power) for same output (power) 6 [] Page

82 Energy transfers Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Energy transfers Difficulty Level Gold Level Booklet Mark Scheme Time Allowed: 58 minutes Score: /57 Percentage: /00 Page

83 M. (a) (because the) potential of the live wire is 30 V (and the) potential of the electrician is 0 V (so there is a) large potential difference between live wire and electrician charge / current passes through his body allow voltage for potential difference (b) diameter between 3.50 and 3.55 (mm) allow correct use of value of cross-sectional area of 9.5 to 9.9 (mm ) with no final answer given for mark (c) 8000 = I 300 I = 8000 / 300 = = (60 ) R R = / (Ω) Page

84 allow 3.83(Ω) with no working shown for 5 marks answer may also be correctly calculated using P = IV and V = IR if 30 V is used. [] Page 3

85 M. (a) electric current (rate of) flow of (electric) charge / electrons accept with Q and t correctly named potential difference work done / energy transferred per coulomb of charge (that passes between two points in a circuit) accept with W and Q correctly named (b) metals contain free electrons (and ions) accept mobile for free as temperature of filament increases ions vibrate faster / with a bigger amplitude accept atoms for ions accept ions/atoms gain energy accept vibrate more for vibrate faster do not accept start to vibrate electrons collide more (frequently) with the ions or (drift) velocity of electrons decreases do not accept start to collide accept increasing the p.d. increases the temperature ( mark) and (and) resistance increases with temperature ( mark) if no other marks scored (c) 7.8 allow mark for obtaining value.3 from graph Page 4

86 or allow mark for a correct calculation using an incorrect current in the range.-.6 inclusive [7] Page 5

87 M3. (a) (i).6 (W) allow mark for correct substitution ie 3 (%) / 0.3 or their (a)(i) 5 correctly calculated ignore any units (b) (i) any two from: comparison over same period of time of relative numbers of bulbs required eg over hours 5 CFL s required to LED accept an LED lasts 5 times longer link number of bulbs to cost eg 5 CFL s cheaper than LED an answer in terms of over a period of hours CFLs cost 5.50 (to buy), LED costs 9.85 (to buy) so CFLs are cheaper scores both marks an answer in terms of the cost per hour (of lifetime) being cheaper for CFL scores mark if then correctly calculated scores both marks over the same period of time LEDs cost less to operate (than CFLs) any one from: price of LED bulbs will drop do not accept they become cheaper less electricity needs to be generated accept we will use less electricity less CO produced Page 6

88 fewer chips needed (for each LED bulb) fewer bulbs required (for same brightness / light) less energy wasted do not accept electricity for energy [6] Page 7

89 M4. (a) water heated by radiation (from the Sun) accept IR / energy for radiation water used to heat buildings / provide hot water allow for mark heat from the Sun heats water if no other marks given references to photovoltaic cells / electricity scores 0 marks (b) (minutes) = gains mark calculation of time of 0 (seconds) scores marks 3 (c) (i) 50 (kwh) 60(.00) or 6000 (p) an answer of 6000 gains mark allow mark for (0) allow ecf from (c)(i) (iii) 5 (years) an answer of 6000 / 40 or 6000 / their (c) 4 gains marks an answer of 6000 / 60 or 6000 / their (c) gains mark, ignore any other multiplier of (c) 3 (iv) any one from: Page 8

90 will get 40 per year accept value consistent with calculated value in (c)(iii) amount of light is constant throughout the year price per unit stays the same condition of cells does not deteriorate (d) any one from: angle of tilt of cells cloud cover season / shade by trees amount of dirt [3] Page 9

91 M5. (a) air near freezer compartment is cooled or loses energy accept air at the top is cold cool air is (more) dense or particles close(r) together (than warmer air) do not allow the particles get smaller / condense so (cooler) air falls air (at bottom) is displaced / moves upwards / rises do not allow heat rises accept warm air (at the bottom) rises (b) if volume is doubled, energy use is not doubled or volume energy not a constant ratio correct reference to data, eg 500 is 50 but 630 not 300 (c) accept suitable examples, eg advantage: reduces emissions into atmosphere lower input power or uses less energy or wastes less energy costs less to run cost of buying or installing new fridge is insufficient ignore reference to size of fridge disadvantage: Page 0

92 land fill energy waste in production cost or difficulty of disposal transport costs [8] M6. (a) (i) 5.88 (watts) an answer of 5.9 scores marks allow mark for correct substitution ie 0.4 = allow mark for an answer of or allow 4 their (a)(i) correctly calculated (b) (i) input power / energy would be (much) less (reducing cost of running) accept the converse electricity is insufficient (also) produce less waste energy / power accept heat for waste energy (as the waste energy / power) increases temperature of the cabinet so cooler on for less time line graph Page

93 need to get both parts correct accept scattergram or scatter graph both variables are continuous allow the data is continuous (c) number of bulbs used-halogen=4 (LED=) total cost of LED = = 97.0 accept a comparison of buying costs of halogen 36 and LED 30 total cost of halogen= 4 x x 6.00 = 40 or buying cost of halogen is 36 and operating cost is 384 accept a comparison of operating costs of halogen 384 and LED 67.0 allow for 3 marks the difference in total cost is 3.80 if the number 4 has not been credited statement based on correct calculations that overall LED is cheaper must be both buying and operating costs an alternative way of answering is in terms of cost per hour: buying cost per hour for LED = 0.065p/ buying cost per hour for halogen = = 0.075p/ a calculation of both buying costs scores mark operating cost per hour for LED = = 0.4p/ operating cost per hour for halogen= = 0.8p/ a calculation of both operating costs scores mark all calculations show a correct unit all units correct scores mark Page

94 statement based on correct calculations of both buying and operating costs, that overall LED is cheaper correct statement scores mark [] Page 3

95 Static electricity Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Static electricity Difficulty Level Bronze Level Booklet Mark scheme Time Allowed: 49 minutes Score: /49 Percentage: /00 Page

96 M. (a) Level (3 4 marks): A detailed and coherent explanation is provided. The student makes logical links between clearly identified, relevant points. Level ( marks): Simple statements are made, but not precisely. The logic is unclear. 0 marks: No relevant content Indicative content friction (between cloth and rod) causes electrons (to) move from the acetate rod or to the cloth (net) charge on cloth is now negative (net) charge on rod is now positive 4 (b) there is a force of attraction between the acetate rod and the cloth (reason) unlike charges attract or negative charges attract positive charges (c) increase (d) (J) Page

97 accept.5 (J) with no working shown for marks [9] Page 3

98 M. (a) (i) (bottom or other ends) move apart or repel accept they move apart have same charge accept both have negative charge (from part (b) do not credit both have positive charge same or like charges repel not just opposite charges attract (b) positive electrons cloth polythene accept strips (c) (i) conductors accept metals insulators accept non-conductors/poor conductors do not credit non-metals [9] Page 4

99 M3. (a) becomes (electrically) charged or description of electron movement for mark (b) comb attracts paper for mark (c) charge/electricity gone to Earth/body for mark each [4] Page 5

100 M4. (a) (i) electrons jumper positive accept protons accept + (iii) positively charged accept any clear way of indicating the answer (b) (i) copper it is an (electrical) conductor only accept if copper is identified do not accept it conducts heat accept it conducts heat and electricity accept copper is the best conductor accept correct description of conduction current [7] Page 6

101 M5. (a) repel opposite attract correct order only (b) refuelling an aircraft reason cannot score if refuelling aircraft is not chosen a spark may cause an explosion / fire / ignite the fuel accept the static for a spark accept named fuel there must be a consequence of having a spark do not accept answers in terms of people getting a shock or electrocuted [5] Page 7

102 M6. (a) (i) electrons a positive (forces are) equal accept (forces are)the same forces are balanced is insufficient (forces act in) opposite directions accept (forces) repel both sides have the same charge is insufficient (b) aluminium [5] Page 8

103 M7. (a) fleece rubs against shirt it refers to the fleece or friction (between fleece and shirt) (causing) electrons to transfer from one to the other accept a specific direction of transfer do not accept charge for electrons positive electrons negates this mark movement of protons negates this mark (b) Electrical charges move easily through metals. An electric current is a flow of electrical charge. (c) (i) copper reason only scores if copper chosen (good electrical) conductor accept it is a metal any mention of heat conduction negates this mark lower than (iii) accept any sensible suggestion,eg: too many variables (to control) lightning strikes / storms are random / unpredictable Page 9

104 do not know which building will be struck do not know when a building will be struck do not know when lightning will happen (very) difficult to create same conditions in a laboratory lightning storms are not the same it is not safe is insufficient do not accept lightning does not strike the same place twice [8] Page 0

105 Static electricity Mark Scheme Level GCSE (9-) Subject Physics Exam Board AQA Topic 4. Electricity Sub-Topic Static electricity Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 45 minutes Score: /45 Percentage: /00 Page

106 M. (a) 450 allow mark for correct substitution, ie provided no subsequent step shown (b) (i) friction between child ( s clothing) and slide accept friction between two insulators accept child rubs against the slide accept when two insulators rub (together) causes electron / charge transfer (between child and slide) accept specific reference, eg electrons move onto / off the child / slide reference to positive electrons / protons / positive charge / atoms transfer negates this mark answers in terms of the slide being initially charged score zero all the charges (on the hair) are the same (polarity) accept (all) the charge/hair is negative / positive accept it is positive/negative charges / hairs are repelling both parts should be marked together (iii) charge would pass through the metal (to earth) accept metal is a conductor accept metal is not an insulator accept there is no charge / electron transfer accept the slide is earthed accept metals contain free electrons [7] Page

107 M. (a) (i) Ends have charge Which is opposite on each rod Attracts (b) (i) Repulsion Ends have same charge (c) Electrons move between cloth and rod Where gather is negative Where move from is positive 3 [8] Page 3

108 M3. (a) clothing and seat rub together accept friction between clothing and seat electrons transfer from seat to driver or electrons transfer from driver to seat accept electrons transfer on its own if first mark scores an answer in terms of rubbing, between clothing and seat and charge transfer without mention of electrons gains mark an answer in terms of friction / rubbing and electron transfer without mention of clothing and seat gains mark (b) (i) how wet the air is affects charge (build up) accept humidity affects charge or damp air is a better conductor or damp air has a lower resistance do not accept fair test or as a control unless explained No it was only the lowest under these conditions accept answer in terms of changing the conditions may change the results or No there are lots of other materials that were not tested or Yes the highest value for cotton is smaller than the lowest value for the other materials do not accept results show that it is always less / smallest [4] Page 4