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Name: _______________________________________________ P1 topic 5 Date: Time: Total marks available: Total marks achieved: ______ Questions Q1. The photograph shows a laptop computer plugged into the 230 V mains. (a) The laptop is left on standby. Its power consumption from the mains is 3.2 W. The cost of 1 kWh of electrical energy is 14 p. Calculate the cost of leaving the laptop on standby for 24 hours. (3) cost = ........................................................... p (b) When the laptop is in normal use, its power consumption from the mains is 97 W. Calculate the current drawn from the mains. (3) current = ........................................................... A (c) The transformer shown in the photograph steps down the mains voltage of 230 V to 9.2 V. The primary coil of the transformer has 4700 turns. (i) Calculate the number of turns on the secondary coil. (3) number of turns = ........................................................... (ii) The laptop is switched on and works normally for 2 minutes. Which graph shows the energy supplied by the mains in this time? Put a cross ( ) in the box next to your answer. (1) (Total for question = 10 marks) Q2. * Some research has been carried out into replacing fluorescent lamp fittings with LED fittings. The data in the table is taken from the report of a trial using LEDs to light stairwells and corridors in a large building. Use the information to discuss the benefits of replacing fluorescent fittings with LED fittings. 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Q3. *Some students found this information about an energy saving lamp and a filament lamp that give out almost the same amount of light. Describe the advantages and disadvantages of each type of lamp. (6) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q4. Distribution of electricity (a) Scientists say that graph 1 shows an alternating current while graph 2 shows a direct current. The two graphs differ in several ways. State the difference between the currents which makes one alternating and the other direct. (1) .............................................................................................................................................. .............................................................................................................................................. (b) A transformer is 100% efficient. It has 200 turns on the primary coil and 3000 turns on the secondary coil. The input voltage is 55 V. (i) Show that the output voltage is about 800 V. (3) (ii) Calculate the current in the secondary coil when the current in the primary coil is 0.50 A. (2) current in secondary coil =............................... A *(c) The diagram shows how electricity produced at a power station is transmitted to distant houses. Transformers R and S are not 100% efficient. By using transformers, energy losses in the transmission lines are reduced. Explain how this reduction is achieved, even though some energy is wasted in the transformers themselves. (6) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q5. The diagram shows a simple generator connected to a lamp. The magnet is made to spin at a steady speed. The ammeter gives a reading of 1.5 A. The voltmeter gives a reading of 6 V. (i) Calculate the output power of the generator. (2) .............................................................................................................................................. (ii) State two changes to the design of the generator that would give a larger output power for the same speed of rotation. (2) .............................................................................................................................................. .............................................................................................................................................. (iii) This generator supplies an alternating current (AC) to the lamp. Other types of generators supply a direct current (DC). Describe the difference between charge movement in a direct current and in an alternating current. (2) .............................................................................................................................................. .............................................................................................................................................. Q6. Electrical power (a) The photograph shows Russell’s wind-up torch. Inside the torch is a small generator. (i) Russell turns the handle and the lamp lights up. How could Russell make the lamp brighter? (1) .............................................................................................................................................. .............................................................................................................................................. (ii) Which of these spins round in the generator? Put a cross ( ) in the box next to your answer. (1) A a lamp B a battery C a transformer D a magnet (iii) Russell turns the handle in the other direction. Explain what happens to the lamp. (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (b) The photograph shows Alan’s bike-powered generator. Alan pedals at a steady speed. (i) The output voltage of the generator is 12.3 V. The output current is 8.00 A. Calculate the output power of the generator. (2) output power = ............................................... W (ii) Alan supplies 15 600 J to the generator in 120 s. Calculate the input power to the generator. (2) input power = .............................................. W (c) Electricity can be generated on a large scale from renewable resources. Describe how electrical energy is obtained from one named renewable resource. (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q7. (a) Eric owns a small farm where chicks are hatched from eggs. He is considering generating his own electricity to heat and light a barn rather than using electricity from the National Grid. This graph shows how the energy output varies with wind speed for two different wind turbines, A and B. The average wind speed at Eric's farm is 13 mph. The total heating and lighting in the barn requires 6000 kW h of electrical energy each year. (i) Use the data in the graph to recommend the best turbine for Eric's barn. (1) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (ii) Eric pays 14p per kW h for electrical energy supplied by the National Grid. Calculate how much he could expect to save each year by using the energy from this wind turbine to heat and light the barn. (2) .............................................................................................................................................. (iii) Eric looks at the cost of installing the turbine. State how he should work out the payback time. (1) .............................................................................................................................................. .............................................................................................................................................. (iv) The chicks need to be kept warm at all times. Eric uses halogen lamps to provide heat and light for most of the day. Eric thinks about changing his halogen lamps for energy saving lamps. Suggest why this might not actually be a benefit. (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. *(b) There are several large-scale energy resources which are suitable alternatives to fossil fuels in some situations. Two of these alternatives are hydro-electric power and solar power. Compare hydro-electric power with solar power as energy resources for the large-scale generation of electricity. 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(Total for Question is 12 marks) Q8. Generating electricity The photographs show two different methods of generating electricity. Photograph A shows a wind-powered generator on the roof of a house. Photograph B shows the inside of an oil-fired power station which is connected to the National Grid. (a) The table shows some information about the wind-powered generator. cost (including installation) £2500 electrical energy produced in one year 900 kWh Electricity from the National Grid costs 15 p per kWh. Calculate the payback time for the wind-powered generator. (3) payback time = .............................................................................. years (b) Transformers are used on a small scale in the home and on a large scale in the National Grid. (i) The transformer for an electric toothbrush charger steps down the mains voltage to 9.0 V. The mains voltage is 230 V. The transformer has 690 turns on its primary coil. Calculate the number of turns on the secondary coil. (3) number of turns = .............................................................................. *(ii) The National Grid transmits electricity around the country. Explain how using transformers makes the transmission of electrical energy more efficient. (6) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q9. (a) The picture shows a wind-powered generator used to produce electricity for a house. (i) The table shows some electrical components. Put ticks in the table next to the two components the generator must contain. (2) (ii) Explain why the voltage produced by this wind-powered generator is not always the same. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (iii) It would cost the homeowner 15 p to buy 1.0 kW h of electrical energy from the National Grid. His generator has a maximum power of 2.0 kW. The generator produces energy at this maximum power for 3 hours. Calculate how much it would cost to buy the same amount of energy from the National Grid. (2) cost = ........................................................... p (b) An electric kettle is plugged into a 230 V mains supply. It has a power of 2.5 kW. Use this equation to calculate the current in the kettle. (3) current = ........................................................... A (c) Suggest why a 2 kW wind-powered generator may not supply all the electrical energy needed in a house. (1) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. Q10. Solar power (a) Complete the sentence by putting a cross ( ) in the box next to your answer. The output power of a solar panel is the rate of transfer of (1) A current B electrons C energy D voltage (b) A solar panel generates direct current. (i) Describe the difference between direct current and alternating current. (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (ii) The output from the solar panel is 60 V. State why a transformer cannot be used to increase this voltage. (1) .............................................................................................................................................. .............................................................................................................................................. (c) Homeowners are being encouraged to fit solar panels to the roofs of their homes. Explain why using solar panels to generate electricity for the National Grid benefits the environment. (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (d) A homeowner fits a solar panel to her roof. The cost of the solar panel is £4800. The solar panel supplies an average of 800 kW h of electrical energy to the National Grid each year. The homeowner is paid 40p for each kW h of energy supplied to the National Grid. Calculate the payback time for the solar panels by selling energy to the National Grid. (3) payback time = ......................................................... years Mark Scheme Q1. Q2. Indicative Content QWC Level 1 * 0 1-2 Mark A discussion including some of the following points improved lighting levels for LEDs energy savings per year for LEDs or calculation of payback time calculation of energy savings over lifetime of LEDs or calculation of monetary savings by using LEDs per year link to savings in fossil fuels for LEDs or link to reduced CO2 produced for LEDs and reduced global warming comparison of lifetimes and (6) maintenance cost No rewardable content a limited discussion of benefits using some pieces of the information provided, e.g. LEDs last 40 000 hours longer and the lighting levels are 200% brighter. the answer communicates ideas using simple language and uses limited scientific terminology spelling, punctuation and grammar are used with limited accuracy 2 3-4 a simple discussion of benefits using some pieces of the information and processing one of them OR 2 processed pieces of information. e.g. LEDs save 3000 kW h of energy each year and are much brighter. The money they save each year compared to fluorescents is £420. OR The payback time for the LEDs is about 5 years and in that time they would have to pay for the fluorescent lights to be replaced 5 times. the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy 3 5-6 a detailed discussion of benefits using processed information covering more than half of the data points in the table e.g. LEDs use less energy each year and this means that fossil fuel reserves are not used up as quickly. The LEDs save £420 each year and have a payback time of about 5 years. the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors Q3. Indicative Content Mark (6) QWC * A discussion including some of the following points Level 1 0 1-2 No rewardable content A limited description of one advantage or one disadvantage e.g. energy saving lamps last a long time/ filament lamps get very hot OR A correct value quoted from information with no comparison. The answer communicates ideas using simple language and uses limited scientific terminology Spelling, punctuation and grammar are used with limited accuracy 2 3-4 A simple description of two different advantages / disadvantages e.g. energy saving lamps cost more but last longer / filament lamps have a short life time and use more power OR Correct values quoted from table and used to provide two comparisons without calculations the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy 3 5-6 A detailed description of two different advantages / disadvantages using a quantitative comparison. e.g. energy saving lamps cost 5 times more but last 10 times longer. / Energy saving lamps produce 4 times as much light energy for every 100J of electrical energy supplied and are much more efficient. / Energy saving lamps last 9,000 hours longer than and they use less power. the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors Q4. Question Number (a) Answer Acceptable answers Mark alternating current can take positive and negative values RA (1) Question Number (b)(i) Answer a.c. above and below zero /the line a.c. goes one way and then the other RA Acceptable answers (1) Mark substitution: (1) Allow substitution and transposition in either order if clear transposition: (1) Question Number (b)(ii) Question Number QWC evaluation / comment: (1) 825(V) / which is about 800 (V) Answer • power input = power output (1) • I = 0.033 (A) (1) *(c) Correct comparison of ratios scores 3 (15 and 14.5, 0.067 and 0.069) Acceptable answers (3) Mark power input = 55 x 0.5 (W) power input = 27.5 (W) I = 0.034 (A) Give full marks for correct answer no working Indicative Content (2) Mark An explanation linking some of the following points Basic ideas• • transmission lines have resistance • the current warms the transmission wires • energy is wasted as heat • transformers change voltage and/or current • R increase the voltage / RA for S • R decrease the current / RA for S Linked ideas• the long transmission lines have high resistance • power depends on both current and voltage • power = current × voltage (P = I × V) • at high voltage, the same (6) power needs less Level 1 0 1-2 2 3-4 3 5-6 current • correct mention of turns ratio related to voltage change • a smaller current in a wire produces less heat • high voltage transmission saves more energy than is lost in the transformers No rewardable material • a limited explanation including some relevant details e.g. R steps up the voltage, S steps it down • the answer communicates ideas using simple language and uses limited scientific terminology • spelling, punctuation and grammar are used with limited accuracy • a simple explanation relating operation of transformers to heat loss in transmission lines and/or transformers e.g. R steps up the voltage so that less heat is lost in transmission lines or high voltage transmission saves more energy than is lost in the transformers • the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately • spelling, punctuation and grammar are used with some accuracy • a detailed explanation relating operation of transformers to current and energy losses in transmission lines and/or transformers e.g. R steps up the voltage so that, for the same power, I is less meaning less heat is lost in transmission lines • the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately • spelling, punctuation and grammar are used with few errors Q5. Answer (i) Substitution (1) 1.5 × 6 Evaluation (1) 9 (W) Ignore any unit given by candidate. (ii) More turns on the coil (1) More powerful/stronger magnet(s) (1) (iii) A description including in one direction only for DC (1) reversing direction for AC (1) Acceptable answers Power of 10 error max 1 mark Give full marks for correct answer with no working shown Wrap coils on iron (core/former)/ more coils/twists/loops. Bigger coil is insufficient. More magnets. Bigger/larger magnet is insufficient. Ignore increase speed of rotation 'DC goes straight' is insufficient AC switches/changes direction OR moves to and fro 'AC goes different ways' is insufficient. Diagram with labelled arrows could get 2 marks. Mark (2) (2) (2) Q6. Question Number (a)(i) Question Number (a)(ii) Question Number (a)(iii) Question Number (b)(i) Question Number (b)(ii) Question Number (c) Answer turn faster Answer D Answer Acceptable answers Mark Acceptable answers (1) Mark Acceptable answers (1) Mark An explanation linking two of the following points the lamp (still) lights (1) still relative movement (between magnet and coil) (1) because current / potential difference (p.d.) still produced (1) Answer generators work in either direction substitution (1) (output power =) 8.00 × 12.3 evaluation (1) 98.4 (W) Answer give full marks for correct answer, no working substitution (1) (input power =) 15600 ÷ 120 evaluation (1) 130 (W) Answer give full marks for correct answer, no working A description including the following points in a logical order name of method (1) e.g. HEP, geothermal, wind appropriate transducer (1) e.g. water turbine, steam turbine, wind turbine correct energy transfer described e.g. wind → electrical dam for water turbine Acceptable answers Acceptable answers Acceptable answers (2) Mark (2) Mark (2) Mark (2) Q7. Answer (ai) (aii) (aiii) (aiv) QWC Model A because Model A (can produce up to )7200kWh per year (at 13mph) / will produce 6000 kWh (with given wind speed). (1) Substitution (1) 0.14 × 6000 Evaluation (1) (£)840 Acceptable answers Model B produces less than 6000kWh per year at 13mph /requires wind speed of more than 13mph to produce 6000kWh Allow incorrect conversion of p to £ such as 0.014 × 6000 for 1 mark only 84 000 p correct answer with no working shown gains both marks Divide the installation £840 for annual cost by the annual saving saving (to find the time in years) (1) A suggestion linking not get hot / (energy saving produce so much lamps) would not heat transfer so much reverse argument thermal energy (1) such as insufficient he may have to use heat for chicks to additional heating / thrive (Ignore lights (which would references to light cost money to run/ output.) purchase) (1) *(b) Mark (1) (2) (1) (2) Indicative Content Mark A discussion including some of the following points Both HEP and Solar power are renewable Both HEP and Solar power would save fossil fuels HEP only possible in some locations HEP requires reservoirs and damming of rivers This can damage environment /takes a lot of land out of use Energy from (6) Level 1 0 1-2 solar power installation is currently much less than energy from fossil fuel powered station Solar power only suitable in certain locations Solar power reliability dependent on constant sunshine Neither of them cause atmospheric pollution No rewardable content a limited description such as at least one relevant detail of each resource eg: Solar power doesn't give off atmospheric pollution. HEP generates more power than solar power. the answer communicates ideas using simple language and uses limited scientific terminology spelling, punctuation and grammar are used with limited accuracy 2 3-4 a simple discussion such as one which gives comparisons between the two or at least an advantage and disadvantage of both. eg: HEP does not use fossil fuels but it can damage the environment where is it located. Solar power will never run out but it requires lots of light/land. the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy 3 5-6 a detailed comparison such as one which relates advantages and disadvantages of both HEP and solar power to a particular situation for possible large scale use e.g.: Solar power uses a renewable energy source but it currently does not produce as much energy as fossil fuel station where there is little sunlight. HEP can produce a lot more energy where there are hills and water but only possible in certain geographical locations. the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors Q8. Question Number (a) Question Number (b)(i) Answer Acceptable answers substitutions (2) (saving per year =) 900 × 0.15 (payback time =) 2500/135 evaluation (1) 18.5 (years) Answer £135 give 3marks for correct answer, no working Acceptable answers (3) Mark Acceptdeither order for transformation / substitution give 2 marks for correct answer, no working evaluation (1) 27 Question Number QWC Mark Indicative content *(b)(ii) (3) Mark Basic ideas• transforme rs change voltage and/or current • transformers use a.c. • the current warms the transmission wires • step-up transformers increase the voltage • step-up transformers decrease the current • energy is wasted Linked• power depends on both current and voltage • power = current × voltage (P = I × V) • at high voltage, the same power needs less current • correct mention of turns ratio related to voltage change • a smaller current in a wire produces less heat Including reasons• when you use a higher (6) Level 1 0 1-2 2 3-4 3 5-6 voltage, the current is lower. With lower current, the amount of heat produced is less. If less heat is lost, the efficiency is greater. • correct use of (P = I × V) to show that current is less in the transmission wires. Less heat is lost because the current is lower. If less heat is lost, the efficiency is greater. • current wastes heat in wires. Using a higher transmision voltage, and therefore a lower current, saves more energy in the transmission wire than is lost in the transformers no rewardable material • basic relevant ideas, not linked and no explanation or reason • e.g. the current warms the transmission wires • the answer communicates ideas using simple language and uses limited scientific terminology • spelling, punctuation and grammar are used with limited accuracy • detailed comments linking ideas • e.g. a smaller current in a wire produces less heat • the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately • spelling, punctuation and grammar are used with some accuracy • full explanation with reasons • e.g. transformers are used to reduce the current so that the heat loss is less and efficiency is more • the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately • spelling, punctuation and grammar are used with few errors Q9. Q10. Question Number (a) Question Number (b)(i) Question Number (b)(ii) Question Number (c) Answer C Answer a description including the following • direct current (the flow of charge) is only in one direction (1) • alternating current (the flow of charge periodically) changes / reverses direction / eq (1) Answer Acceptable answers Acceptable answers d.c stays positive/negative only goes positive and negative Acceptable answers any one of the following • transformers only change alternating voltages / currents • transformers will It is not not work with direct alternating / direct current current Answer Acceptable answers An explanation conserving fossil linking any two of fuel reserves the following reduction of • reduction of correctly named fossil fuels burnt pollutant / (1) • less reliance greenhouse gas on fossil fuels (1) solar energy is • reduction of renewable fossil greenhouse gases fuels are non/ pollution/global renewable warming (1) • increased use of renewable energy source (1) • less use of nonrenewable energy source (1) • reduce need for additional power station building (1) • reduction of negative impact of Mark (1) Mark (2) Mark (1) Mark (2) Question Number (d) specified type of power station (1) Answer substitution (1) 800 × 0.4 / 800 × 40 evaluation of payment (1) (£)320 / 32000 (p) evaluation of payback time (1) 15 (years) Acceptable answers 4800 / 0.4 = 12000 Kwh (to be sold) takes 12000 / 800 years substitution and transposition can be in either order allow power of 10 error in 15 for (2) give full marks for correct answer, no working Mark (3)