Physics required practical booklet

Transcription

1 Physics required practical booklet Each section contains: From the specification The start of each section contains the main aim of the practical and a diagram taken from AQA. Overview A short summary of what you will do in the practical, what AQA may ask you about this investigation during the examinations. A full description of the method has not been included because you will have written this during your investigation. Exam questions one or more exam questions covering the concepts relating to that required practical. Answers to exam questions. Paper may ask you about practical activities,2,3,4 and 5 Paper 2 may ask about practical activities 6,7,8,9 and 0 Page number Required practical activity Specific heat capacity 9 2 Thermal insulation (Physics only) Resistance 24 4 IV Characteristics Density 3 6 Light (Physics only) 34 7 Force and extension Acceleration Waves 47 0 Radiation and absorption Required practical activity Specific heat capacity (Trilogy and Physics) An investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored. Overview In this practical you will be required to measure the mass of a block (usually kg to make calculations easy) and heat it up. Using the temperature change, energy supplied (by measuring the time and power of the heater) and the mass of the block you can calculate the specific heat capacity of the block. In our case we used Aluminium but you can do this with copper or both. You could be asked why the readings were not exact during the measurements you take (usually the answer to this is that some energy is lost to the surroundings) or as the question below shows, you could be asked about some other persons experiment and provided with results. V 2V A

2 SHC Exam questions with answer SHC Q.A student used the apparatus in Figure to obtain the data needed to calculate the specific heat capacity of copper. Figure The initial temperature of the copper block was measured. The power supply was switched on. The energy transferred by the heater to the block was measured using the Joulemeter. The temperature of the block was recorded every minute. The temperature increase was calculated. Figure 2 shows the student s results. Figure 2 Energy transferred to copper block in joules (a) Energy is transferred through the copper block. What is the name of the process by which the energy is transferred? Tick ( ) one box. Conduction Convection Radiation ()

3 (b) Use Figure 2 to determine how much energy was needed to increase the temperature of the copper block by 35 C.... joules () (c) The copper block has a mass of 2 kg. Use your answer to part (b) to calculate the value given by this experiment for the specific heat capacity of copper. Give the unit. Specific heat capacity =... (3) (d) This experiment does not give the correct value for the specific heat of copper. Suggest one reason why. () (Total 6 marks) SHC Q2.Figure shows a kettle a student used to determine the specific heat capacity of water. Figure vladimirkim3722/istock/thinkstock The student placed different masses of water into the kettle and timed how long it took for the water to reach boiling point. The student carried out the experiment three times.

4 The student s results are shown in the table below. Time for water to boil in seconds Mass of water in kg 2 3 Mean Mass change in temperature in kg C Energy supplied in kj (a) Suggest how the student was able to ensure that the change in temperature was the same for each mass of water. (2) (b) Calculate the uncertainty in the student s measurements of time to boil when the mass of water was.75 kg. Uncertainty =... s (2)

5 (c) The power rating of the kettle is 2.20 kw. Calculate the average electrical energy used by the kettle, in kj, for.75 kg of water to reach boiling point. Average energy =... kj (2) (d) Use information from the table above to calculate the change in temperature of the water during the investigation. Change in temperature =... C (2) (e) The student plotted a graph of energy supplied in kj against mass change in temperature in kg C. Figure 2 shows the graph the student plotted. Figure 2 Use data from the table above to plot the four missing points. Draw a line of best fit on the graph. (3) (f) Use the graph to determine the mean value of the specific heat capacity of water, for the student s investigation. Specific heat capacity of water =... J / kg C (4)

6 (g) The student s value for the specific heat capacity of water was greater than the accepted value. Suggest why. () (h) The kettle used in the experiment had a label stating that the power rating of the kettle was 2.2 kw. The student did not measure the power of the kettle. Suggest why measuring the power of the kettle may improve the student s investigation. () (Total 7 marks) SHC answers (a) conduction (b) (c) 500 their (b) = 2 x c x 35 correctly calculated scores 2 marks allow mark for correct substitution, ie = 2 x c x 35 or their (b) = 2 x c x 35 2 J / kg C (d) energy lost to surroundings or energy needed to warm heater accept there is no insulation (on the copper block) do not accept answers in terms of human error or poor results or defective equipment [6]

7 M9.(a) water boils at the same temperature each time control starting temp by allowing enough time for water and kettle to reach room temperature (b) uncertainty = ( ) / 2 uncertainty = ± 2 (s) ignore missing ± (c) (Energy transferred = Power time) E = E = 660 (kj) (d) allow 660 (kj) without working shown for 2 marks allow answer calculated using incorrect value for t (298 or 302) for mark (mass change in temperature) / mass allow mark for any correct pair of values from the table 80 ( C) eg 20 / 0.25 (e) allow 80 ( C) without working shown for 2 marks four points plotted correctly allow mark for three correctly plotted points 2

8 ecf their 5.3 allow ± mm accurate line drawn line should be straight and drawn with a ruler (f) line must not go through the origin values read correctly from graph correct conversion into J correct use of y / x value in range (g) allow value in range without working shown for 4 marks some of the energy supplied does not raise the temperature of the water some of the energy is wasted is insufficient (h) (the power of the kettle may not be 2.2kW) (by measuring the power) the student can accurately calculate the amount of energy supplied to each mass of water [7]

9 GCSE Physics required practical activity No. 2 Thermal insulation (physics only) Teachers notes Required practical activity Investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material. Overview This investigation is broken down into two main parts. For each part you will be measuring the rate of cooling of water placed in insulated containers. In the first part of the experiment you insulate containers with different materials and see which cools faster. In the second experiment you insulate containers with different thicknesses of the same material and again see which cools faster. For both experiment you will plot a cooling curve and so they may ask you about plotting graphs in the exam. Also you are required to control a lot of the variables in this investigation so they may ask you about accurately measuring volume, length temperature or time. Exam questions Thermal insulation Q. (a) warm. The diagram shows a ski jacket that has been designed to keep a skier The jacket is made from layers of different materials. (i) The inner layer is shiny to reduce heat transfer. (ii) Which process of heat transfer will it reduce?... Why is the layer of fleece good at reducing the transfer of heat from a skier s body? () ()

10 (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 ()

11 (iii) Look at the graph line for fleece K. Estimate what the temperature of the water in the can wrapped in fleece K would be after 40 minutes.... () (iv) Which type of fleece, J, K, L or M, should the student recommend to be used in the ski jacket?... Give a reason for your answer (2) (Total 7 marks)

12 Q2. A student had read about a glacier that had been covered in insulating material. The idea was to slow down the rate at which the glacier melts in the summer. She investigated this idea using the apparatus shown in the diagram. (a) These are the steps taken by the student. Measure 30 cm 3 of cold water into a boiling tube. Place the boiling tube 25 cm from an infra red lamp. Record the temperature of the water. Switch on the infra red lamp. Record the temperature of the water every minute for 5 minutes. Repeat with boiling tubes covered in different insulating materials. (i) Why did she use an infra red lamp?... () (ii) Name one control variable in this investigation.... () (iii) Give one advantage of using a temperature sensor and data logger instead of a glass thermometer to measure temperature ()

13 (b) The results of the investigation are shown in the graph. (i) Why did the student use a boiling tube with no insulation? () (ii) From her results, what should she recommend is used to insulate the glacier?... () (iii) Explain why the insulation recommended by the student will reduce the heat transfer from the Sun to the glacier (2)

14 (c) Explain, in terms of particles, how heat is transferred through the glass wall of a boiling tube. (2) (Total 9 marks) Thermal insulation answers M. (a) (i) radiation (ii) traps (small pockets of) air do not accept it s an insulator do not accept reduces conduction and / or convection do not allow it doesn t allow heat to escape (b) (i) bigger temperature difference (between the water and surroundings)at the start (than at the end) do not accept water is hotter (ii) starting temperature (of the water) accept thickness of fleece do not accept same amount of fleece do not accept thermometer / can do not accept time is the same (iii) 8 ( C) correct answer only (iv) M

15 smallest temperature drop (after 20 mins) cannot score if M is not chosen accept it s the best insulator accept smallest loss in heat accept keeps heat / warmth in for longer [7] M2. (a) (i) as a source of thermal radiation accept heat for thermal radiation accept to act as the Sun do not accept sunlight alone (ii) any one from: volume of water accept amount for volume distance between lamp and boiling tube initial / starting temperature of water same room temperature do not accept time or same insulation material (iii) any one from: greater sensitivity / precision do not accept more reliable (negates mark) could link to a computer for (automatic) data analysis could take more frequent readings reduces instrument reading error accept more accurate do not accept easier to use on its own (b) (i) acts as a control accept to be able to make a comparison accept to see the difference do not accept to make it a fair test OWTTE on its own

16 (ii) (iii) (plastic) foam and aluminium foil (aluminium) foil is a poor absorber of thermal radiation accept heat / infra red for thermal radiation or (aluminium) foil is a (good) reflector of thermal radiation do not accept reflects sunlight on its own (plastic) foam traps air which is a (good) insulator accept (plastic) foam is a poor conductor / (good) insulator do not accept the material is a good insulator / poor conductor (c) particles vibrate with a bigger / stronger amplitude / faster / with more (kinetic) energy accept particles vibrate more do not accept start to vibrate only energy transferred by collisions with other particles do not accept answers in terms of free/mobile electrons [9]

17 GCSE Physics required practical activity 3: Resistance (Trilogy and Physics) Use circuit diagrams to set up an appropriate circuit to investigate a factor/the factors that affect the resistance of an electrical component. This should include: the length of a wire at constant temperature combinations of resistors in series and parallel. Overview Again there are two parts to this investigation. The first requires you to investigate the resistance of different lengths of wire. The second requires you to investigate resistance in both series and parallel circuits. In the first part of the experiment you will produce a graph of resistance against length and this should create a straight line graph through the origin point o.o. AQA have said the following This experiment is a good one to use to discuss zero error as it is hard to attach the crocodile precisely to the zero end of the wire so I would guess that they will ask you about zero error and you should be ready for it. A zero error is when the measuring apparatus does not return to zero when it should. This could be the ammeter in your investigation not returning to zero when the power pack is switched off. If possible the ammeter should be recalibrated to read zero or you should subtract the zero error from all measured readings (so if it reads 2A when it should be 0A you should subtract 2A from all readings). The second part of the experiment may also ask about measuring equipment but it is more likely that they will link this to the rules for the behaviour of current and voltage in series and parallel or ask you to draw series and parallel circuits. Resistance of a wire Exam questions Q. (a) The diagram shows the circuit used to investigate the resistance of a material. The diagram is incomplete; the ammeter and voltmeter are missing.

18 (i) (ii) Draw the symbols for the ammeter and voltmeter on the diagram in the correct places. How can the current through the material be changed? (2) () (b) The material, called conducting putty, is rolled into cylinders of different lengths but with equal thicknesses. Graph shows how the resistance changes with length. Graph (i) Why has the data been shown as a line graph rather than a bar chart? () (ii) The current through a 30 cm length of conducting putty was 0.5 A. Use Graph to find the resistance of a 30 cm length of conducting putty. Resistance =... ohms ()

19 (iii) Use your answer to (b)(ii) to calculate the potential difference across a 30 cm length of conducting putty. Show clearly how you work out your answer Potential difference =... volts (2) (c) A second set of data was obtained using thicker pieces of conducting putty. Both sets of results are shown in Graph 2. Graph 2 (i) What is the relationship between the resistance and the thickness of the conducting putty? () (ii) Name one error that may have reduced the accuracy of the results.... ()

20 (iii) How could the reliability of the data have been improved? () (Total 0 marks) Q2.(a) Electrical circuits often contain resistors. The diagram shows two resistors joined in series. Calculate the total resistance of the two resistors. Total resistance =... Ω () (b) A circuit was set up as shown in the diagram. The three resistors are identical. (i) Calculate the reading on the voltmeter Reading on voltmeter =... V (2)

21 (ii) The same circuit has now been set up with two ammeters. Draw a ring around the correct answer in the box to complete the sentence. smaller than The reading on ammeter A 2 will be equal to the reading on ammeter A. greater than () (Total 4 marks)

22 Practical 3 resistance of a wire Answers M. (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 (ii) adjust / use the variable resistor accept change the resistance or change the number of cells accept battery for cell accept change the p.d / accept change the voltage accept increase / decrease for change (b) (i) data is continuous (variable) (ii) 36 (Ω) correct answer only (iii) 5.4 or their (b)(ii) 0.5 allow mark for correct substitution 2 (c) (i) the thicker the putty the lower the resistance answer must be comparative accept the converse (ii) any one from: measuring length incorrectly accept may be different length measuring current incorrectly do not accept different currents measuring voltage incorrectly

23 do not accept different voltage ammeter / voltmeter incorrectly calibrated thickness of putty not uniform meter has a zero error accept any sensible source of error eg putty at different temperatures do not accept human error without an explanation do not accept pieces of putty not the same unless qualified do not accept amount of putty not same do not accept systematic / random error (iii) repeat readings accept check results again accept do experiment again accept do it again accept compare own results with other groups do not accept take more readings [0] M2.(a) 25(Ω) (b) (i) 2(V) allow mark for showing a correct method, ie 6 / 3 2 (ii) equal to [4]

24 Required practical activity 4 IV Characteristics (Trilogy and Physics) Use circuit diagrams to construct appropriate circuits to investigate the I-V characteristics of a variety of circuit elements including a filament lamp, a diode and a resistor at constant temperature. A A ma V V V Overview In this practical you will set up the circuits above and use the ammeter and voltmeter to calculate resistance for each component. Alternately you may have used a digital multimeter to record resistance in Ohms directly. Whichever method you have used you will be required to draw a current voltage graph for each component which will have a specific shape; this is the characteristic of that component. The shapes of the graphs you should plot are shown in the questions below and so these questions may be linked directly to subject knowledge. If not, they could again ask you about correctly measuring current or voltage. As with all of these practicals they could give you an extended answer question to describe how the apparatus should be set up. IV characteristic exam questions Q.A student wants to investigate how the current through a filament lamp affects its resistance. (a) Use the circuit symbols in the boxes to draw a circuit diagram that she could use. 2 V battery variable resistor filament lamp voltmeter ammeter (2)

25 (b) Describe how the student could use her circuit to investigate how the current through a filament lamp affects its resistance. (4) (c) The student s results are shown in Figure. Figure Describe how the resistance of the filament lamp changes as the current through it increases. ()

26 (d) Use Figure to estimate the resistance of the filament lamp when a current of 0.0 A passes through the lamp. Resistance =... Ω () (e) The current potential difference graphs of three components are shown in Figure 2. Use answers from the box to identify each component. diode filament lamp light dependent resistor resistor at constant temperature thermistor Figure (3) (Total marks)

27 M.(a) battery, lamp and ammeter connected in series with variable resistor voltmeter in parallel with (filament) lamp (b) Level 2 (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 ( 2 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 C: Diode []

28 Required practical activity 5 Density (Trilogy and Physics) Use appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume should be determined from the dimensions of regularly shaped objects and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometre or Vernier callipers Overview This practical is relatively simple compared to some of the others as this only requires you to use a ruler, balance and measuring cylinder. This may mean that the exam will ask you about the accuracy of the measuring equipment to be used or its resolution (the smallest measurement the apparatus can accurately make e.g. mm on a normal 30cm ruler). The first part of the experiment is very similar to the subject knowledge which you have been taught about density and requires you to measure the exact volume and mass of a regular shaped object. The second part involves measuring the volume of an irregular shaped object by displacing a volume of water in a measuring cylinder. This part of the practical lends itself to an extended answer question on how to measure density (as shown in the specimen exam question below). Exam question density Q.A student wants to calculate the density of the two objects shown in the figure below. Whitehoune/iStock/Thinkstock, Marc Dietrich/Hemera/Thinkstock Describe the methods that the student should use to calculate the densities of the two objects (Total 6 marks)

29 Q2.The figure below shows a balloon filled with helium gas. (a) Describe the movement of the particles of helium gas inside the balloon. (2) (b) What name is given to the total kinetic energy and potential energy of all the particles of helium gas in the balloon? Tick one box. External energy Internal energy Movement energy () (c) Write down the equation which links density, mass and volume. ()

30 (d) The helium in the balloon has a mass of kg. The balloon has a volume of 0.04 m 3. Calculate the density of helium. Choose the correct unit from the box. m 3 / kg kg / m 3 kg m 3 Density =... Unit... (3) (Total 7 marks)

31 Required practical activity 6 Light Physics only Investigate the reflection of light by different types of surface and the refraction of light by different substances. ray box lens slit incident ray reflected ray block refracted ray Overview During this experiment you will be asked to shine a ray of light through a transparent block and measure the refracted angle and the angle of reflection at the surface. Since this investigation does not require a large amount of measuring equipment the exam may ask you about possible sources of error or uncertainty in your investigation. As you will remember the light ray spreads out as it leaves the glass block so deciding exactly where the middle of the beam is would be counted as the main source of error in this investigation. In the past this has also been used as an extended answer question so you must be familiar how to set up the apparatus and take the readings Exam questions for Light Q.The data given in the table below was obtained from an investigation into the refraction of light at an air to glass boundary. Angle of incidence Angle of refraction

32 (a) Describe an investigation a student could complete in order to obtain similar data to that given in the table above. Your answer should consider any cause of inaccuracy in the data. A labelled diagram may be drawn as part of your answer. (6) (b) State the reason why light is refracted as it crosses from air into glass. () (Total 7 marks)

33 M.(a) Level 3 (5 6 marks): A detailed and coherent plan covering all the major steps is provided. The steps in the method are logically ordered. The method would lead to the production of valid results. A source of inaccuracy is provided. Level 2 (3 4 marks): The bulk of a method is described with mostly relevant detail. The method may not be in a completely logical sequence and may be missing some detail. Level ( 2 marks): Simple statements are made. The response may lack a logical structure and would not lead to the production of valid results. 0 marks: No relevant content. Indicative content place a glass block on a piece of paper draw around the glass block and then remove from the paper draw a line at 90 to one side of the block (the normal) use a protractor to measure and then draw a line at an angle of 20 to the normal replace the glass block using a ray box and slit point the ray of light down the drawn line mark the ray of light emerging from the block remove the block and draw in the refracted ray measure the angle of refraction with a protractor repeat the procedure for a range of values of the angle of incidence possible source of inaccuracy the width of the light ray which makes it difficult to judge where the centre of the ray is 6 [7] (b) velocity / speed of the light decreases allow velocity / speed of the light changes

34 Required practical activity 7 Force and Extension. (Trilogy and Physics) Investigate the relationship between force and extension for a spring. Overview This is a classic Physics experiment to observe Hooke s law and once more this involves the accurate use of a 30cm ruler (could ask about resolution again). During this investigation you must ensure that you work out the extension which should be used to plot a graph of extension against force. This should be a directly proportional relationship (straight line through the origin) and if the graph starts to curve you know that the object has passed the limit of proportionality (its elastic limit). After this point it will no longer return to its original shape when the forces deforming it are removed. The practical requires you to place an unknown mass on the spring and use the extension along with the curve on your graph to determine the weight of the unknown object. So they may directly ask you to do this on data which is given to you in the exam. Force and Extension exam questions Q.A student suspended a spring from a laboratory stand and then hung a weight from the spring. Figure shows the spring before and after the weight is added. Figure (a) Measure the extension of the spring shown in Figure. Extension =... mm () (b) The student used the spring, a set of weights and a ruler to investigate how the extension of the spring depended on the weight hanging from the spring. Before starting the investigation the student wrote the following prediction: The extension of the spring will be directly proportional to the weight hanging from the spring.

35 Figure 2 shows how the student arranged the apparatus. Figure 2 Before taking any measurements, the student adjusted the ruler to make it vertical. Explain why adjusting the ruler was important. (2) (c) The student measured the extension of the spring using a range of weights. The student s data is shown plotted as a graph in Figure 3. Figure 3 What range of weight did the student use? ()

36 (d) Why does the data plotted in Figure 3 support the student s prediction? () (e) Describe one technique that you could have used to improve the accuracy of the measurements taken by the student. (2) (f) The student continued the investigation by increasing the range of weights added to the spring. All of the data is shown plotted as a graph in Figure 4. Figure 4 At the end of the investigation, all of the weights were removed from the spring. What can you conclude from Figure 4 about the deformation of the spring? Give the reason for your conclusion. (2)

37 Required practical activity 8 Acceleration (Trilogy and Physics) Investigate the effect of varying the force on the acceleration of an object of constant mass and the effect of varying the mass of an object on the acceleration produced by a constant force. Equations which are directly linked to this investigation: F = ma a = (v-u) / t Overview In this investigation you are required accurately measure the interrupted time at both of the light gates to give you a change in velocity which you can use to calculate acceleration of the glider. You will change the mass on the weight stack (shown above) and observe the effect on acceleration. This may mean that the exam will ask you about the advantages of using light gates and data loggers in the investigation as opposed to timing it yourself with a stopwatch. The data logger can have a greater resolution than a stopwatch and is also more accurate as you do not rely on the reaction time of the person with the stopwatch (this introduces possible human error and it would be very difficult to accurtly time both results as they are so close together). Another strong possibility is that they will link this directly to one of the equations above so you should be familiar with these and know that for this experiment the acceleration equation could be written as follows. acceleration 2 Note that your required practical sheet also asks you to take repeat readings and use these to calculate a mean. This will reduce the effect of random errors and help to identify possible anomalous results. If you are asked about this you must ensure that you say take repeat readings and calculate the mean/average. Just saying take repeat readings on its own would not be enough to reduce the effect of random error.

38 Exam questions acceleration Q. (a) A shopping trolley is being pushed at a constant speed. The arrows represent the horizontal forces on the trolley. (i) How big is force P compared to force F?... () (ii) Which one of the distance-time graphs, K, L or M, shows the motion of the trolley? Draw a circle around your answer. () (b) Complete the sentence by crossing out the two words in the box that are wrong. Acceleration is the rate of change of ()

39 (c) Three trolleys, A, B and C, are pushed using the same size force. The force causes each trolley to accelerate. Which trolley will have the smallest acceleration? Give a reason for your answer. (2) (Total 5 marks) Q2. A high-speed train accelerates at a constant rate in a straight line. The velocity of the train increases from 30 m/s to 42 m/s in 60 seconds. (a) (i) Calculate the change in the velocity of the train.... Change in velocity =... m/s () (ii) Use the equation in the box to calculate the acceleration of the train. Show clearly how you work out your answer and give the unit. Choose the unit from the list below. m/s m/s 2 N/kg Nm Acceleration =... (2)

40 (b) Which one of the graphs, A, B or C, shows how the velocity of the train changes as it accelerates? Write your answer, A, B or C, in the box. A B C Graph () (Total 4 marks)

41 M. (a) (i) same size (ii) K (b) velocity (c) C greatest mass or because it s heavier accept biggest load accept heaviest or more weight do not accept fuller do not accept more items do not accept it s loaded do not accept loaded most ignore references to time as neutral [5] M2. (a) (i) 2 (ii) 0.2 allow mark for their (a)(i) 60 and correctly calculated m/s 2 accept correct unit circled in list accept ms 2 do not accept mps 2 (b) B [4]

42 Required practical activity 9 Waves (the ripple tank) (Trilogy and Physics) Make observations to identify the suitability of apparatus to measure the frequency, wavelength and speed of waves in a ripple tank and waves in a solid and take appropriate measurements. Overview This practical will be conducted as a teacher demonstration but you will be asked to help out when it comes to measuring the wavelength and the frequency. The wavelength is measured with a ruler by measuring the number of waves which can be seen on the ruler and dividing this by the total length of the ruler (remember to convert your cm/mm into m before performing any calculations). They may ask you how you could improve the accuracy of this part of the experiment and one possible solution could be to take a slow motion video of the waves with a ruler on the screen or a still image; rather than attempting to measure how many waves are present when they are moving relatively quickly. To measure frequency you must count the number of waves passing a point in a sec time (0 seconds) and divide this by the time to find out how many waves are passing that point each second. This works best if many students count the number of waves and we calculate a mean (see the previous practical for why this is an advantage). The second part of the experiment (shown below) does not require the use of measuring equipment other than a m ruler to measure wavelength which has the same resolution as a 30cm ruler and is only used as it is larger and it would introduce inaccuracy by trying to use many 30cm ruler attacked end to end (it is likely that the rulers would not be exactly straight in that case). The frequency is given from the supply so it is likely that if asking you about this experiment, the question will directly be linked to the wave equation.

43 Waves exam questions Q.A ripple tank is used to investigate the behavior of water waves. A bar moves up and down to make the waves. (a) What is the wavelength of each wave in the diagram? Draw a ring around the correct answer. 2 cm 3 cm 6 cm () (b) The ripple tank produces 0 waves in 2 seconds. What is the frequency of the waves? Frequency =... hertz () (c) The bar is made to move faster. It now produces waves with: a frequency of 20 hertz a wavelength of 0.5 cm. Calculate the speed of the water waves in cm/s. Use the correct equation from the Physics Equations Sheet. Show clearly how you work out your answer. Speed =... cm/s (2)

44 (d) A student uses the ripple tank to investigate the relationship between depth of water and speed of waves. The graph shows the student s results. (i) There is one anomalous result. On the graph, draw a ring around this anomalous result. () (ii) On the graph, draw a line of best fit () (iii) Use your line of best fit to find the speed of the wave at a depth of 20 cm. Wave speed =... cm/s () (Total 7 marks) Q2.Some students did an investigation to study the behaviour of waves. The figure below shows a ripple tank that they used to model the behaviour of waves.

45 (a) Complete the wave fronts on the figure above. Show how the wave is refracted as it passes from the shallow region into the deep region. () (b) Explain what happens to the waves as they pass into the deep region. (2) (c) The waves generated on the surface of the water are transverse waves. Describe the differences between longitudinal waves and transverse waves. You may include labelled diagrams to help your answer. (3) (d) Some students investigate the properties of the waves generated in the figure above. Student A says the waves move water from one end of the tank to the other. Student B says that s wrong. Only the waves move, not the water. Suggest what the students could do to decide which of them is correct. (2)

46 (e) Another student uses a ripple tank where all the water is the same depth. She measures the wavelength of each wave as 0.34 m. The period of each wave is 0.42 s. Calculate the speed of the wave. Use the correct equation from the Physics Equation Sheet. Give the unit. Give your answer to three significant figures. Speed =... Unit =... (5) (Total 3 marks)

47 Required practical activity 0 radiation and absorption (Physics only) Investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface. Overview This is a very simple experiment which will also be done as a demonstration. AQA will most likely take the opportunity to ask you directly about placing the surfaces in order of how well they emit infra-red radiation. However they have also said The detector may be an infrared detector with a suitable meter, an infrared thermometer or a liquid-in-glass thermometer with the bulb painted matt black. The last option is likely to have the least resolution. This implies that they may ask you about resolution again and so you should be aware that the greater the resolution of the apparatus used, the greater the accuracy of the experiment. They may aslso ask you was the resolution suitable and you could reply that it was suitable as the digital thermometer we have used had a resolution of 0. 0 C which is much less than any of the differences in temperature between the surfaces (in short we do not need to be that accurate when taking readings which are different by 5 or more 0 C). remember that resolution is the smallest measurement a piece of apparatus can accurately make. Exam questions radiation and absorption Q. A student investigated the effect of shape and colour on heat transfer. The student used metal containers with the same volume but with different shapes and outside colour. The containers were each filled with water at 00 C. After 20 minutes the temperature of the water inside each container was measured. B A C D

48 The results from the investigation are given in the table. Container Colour Temperature after 20 minutes in C Temperature fall in C A White 86 4 B Black 86 4 C White D Black (i) The student uses the results in the table to see if shape has affected heat transfer. Which containers should the student compare to do this?... Give a reason for your answer () (ii) Explain why the temperature of the water in both containers A and B fell by the same amount (2) (iii) A central heating system has several radiators joined together. The hot water goes from the boiler, through each radiator in turn and then back to the boiler for reheating. Give one reason, other than appearance, why it might not be a good idea to paint radiators black () (Total 4 marks)

49 Q2.All objects emit and absorb infrared radiation. (a) Use the correct answer from the box to complete each sentence. dark matt dark shiny light matt light shiny The best emitters of infrared radiation have... surfaces. The worst emitters of infrared radiation have... surfaces. (2) (b) Diagram shows a sphere which is at a much higher temperature than its surroundings. Diagram Energy is transferred from the sphere to the surroundings. The table shows readings for the sphere in three different conditions, A, B and C. Condition Temperature of sphere in C Temperature of surroundings in C A 70 5 B 80 0 C 90 30

50 In each of the conditions, A, B and C, the sphere transfers energy to the surroundings at a different rate. Put conditions A, B and C in the correct order. Give a reason for your answer... (2) (c) Diagram 2 shows a can containing water. A student investigates how quickly a can of water heats up when it is cooler than room temperature. Diagram 2 The student has four cans, each made of the same material, with the following outer surfaces. dark matt dark shiny light matt light shiny

51 The student times how long it takes the water in each can to reach room temperature. Each can contains the same mass of water at the same starting temperature. (i) Which can of water will reach room temperature the quickest? Give a reason for your answer (2) (ii) Apart from material of the can, mass of water and starting temperature, suggest three control variables for the student s investigation (3) (d) The photographs show two different foxes. Fox A Fox B By Algkalv (Own work) [CC-BY-3.0], via Wikimedia Commons EcoPic/iStock Which fox is better adapted to survive cold conditions? Give reasons for your answer (3) (Total 2 marks)

52 Q3. The diagram shows four identical pieces of aluminium. Each had been painted with a different type of paint. A drop of water was placed on each and they were then heated by a radiant heater held about one metre above them. (i) Suggest in which order the pieces of aluminium would become dry. first last () (ii) Explain why you chose your order. (2) (Total 3 marks)

53 M. (i) this mark only scores if a correct pair is chosen and a correct reason given A and C orb and D both required and none other both required and none other (ii) (iii) only one (independent) variableordifferent shapes but the same colour accept only the shape changes B radiates heat faster converse answer in terms of A gains full marks orb is a better emitter (of heat) but B has a smaller (surface) areaorb has a smaller (surface) area: volume ratio allow 2 marks for both lose the same quantity / amount of heat in the same time or both have same rate of heat loss allow mark for both lose the same quantity / amount of heat any one from: transfer a lot of heat (too rapidly) water temperature drops too rapidly accept (significantly) more heat will be lost from the first radiator water too cold for the next radiator mention of absorption of heat negates mark [4] M2.(a) dark matt light shiny (b) B A C biggest temperature difference (80 C) dependent on first mark (c) (i) (the can that is) dark matt best absorber (of infrared radiation) (ii) any three from:

54 same area / shape of can surrounding temperature is the same for all cans same surface underneath cans same position in the room 3 (d) fox A smaller ears thicker fur these minimise energy transfer dependent on first 2 marks [2] M3. (i) D, C or B, in either order, then A tick or cross on the A (ii) matt absorbs energy (better than shiny) the converse arguments are acceptable black absorbs energy (better than white) [3]