PRE LEAVING CERTIFICATE EXAMINATION, 2014 MARKING SCHEME

Transcription

1 *WMS13* PRE LEAVING CERTIFICATE EXAMINATION, 2014 MARKING SCHEME PHYSICS HIGHER AND ORDINARY LEVEL Page 1 of 33

2 GENERAL GUIDELINES In considering this marking scheme the following points should be noted: 1. In many instances only key words are given, words that must appear in the correct context in the candidate s answer in order to merit the assigned marks. 2. Words, expressions or statements separated by a solidus, /, are alternatives which are equally acceptable. 3. Answers that are separated by a double solidus, //, are answers which are mutually exclusive. A partial answer from one side of the // may not be taken in conjunction with a partial answer from the other side. 4. The descriptions, methods and definitions in the scheme are not exhaustive and alternative valid answers are acceptable. 5. The detail required in any answer is determined by the context and manner in which the question is asked and by the number of marks assigned to the answer in the examination paper. Therefore, in any instance, it may vary from year to year. 6. For lack of units, or incorrect units, one mark is deducted, as indicated. 7. Each time an arithmetical slip occurs in a calculation one mark is deducted. Page 2 of 33

3 HIGHER LEVEL Question 1. SECTION A (120 marks) Each question carries 40 mark In establishing the calibration curve for a thermocouple, the following results were obtained, showing the variation of e.m.f. (V), with temperature, (θ). Draw a graph to show the variation of e.m.f. against temperature. (18) Label axes correctly 6 Plot nine points correctly ( 1 for each incorrectly plotted point) 6 Good distribution 6 ( 1 for inappropriate scale) Draw a labelled diagram of the apparatus that could be used in this experiment. (9) Thermocouple in ice 3 Thermocouple in water bath/oil with temperature sensor 3 Thermocouple connected to labelled current or voltage sensor/(digital) multimeter 3 Explain how each quantity was measured. (6) Use a mercury thermometer/temperature sensor in the hot water bath, along with the hot junction. 3 Note the current/voltage value using a sensor/ (digital) multimeter every 10 0 C as the water is heated up. 3 From the graph, find the rate of change of e.m.f. per degree rise in temperature. (7) e.m.f = per o C using slope method. Acceptable range Page 3 of 33

4 Question 2. In an experiment to measure the specific heat capacity of a liquid, a quantity of liquid was heated in a copper calorimeter. The following measurements were obtained: Mass of calorimeter = 53.0 g Mass of calorimeter + liquid = g Initial temperature of calorimeter + liquid = 16 C Final temperature of calorimeter + liquid = 21 C Energy supplied = 1168 J Using these measurements, calculate the value for the specific heat capacity of the liquid given that the specific heat capacity of copper is 390 J kg 1 K 1. (15) Energy lost by heater = energy gained by liquid + calorimeter 3 Energy gained by liquid = m w C l Δθ = C l 5 = 0.448C l J 3 Energy gained by calorimeter = m c C c Δθ = = J J = 0.448C l J J 3 C l = ( )/0.448 = 2376 J Kg 1 K 1 3 ( 1 for incorrect or omission of units) Draw a diagram of the apparatus used in this experiment. (9) red blue Heat source/immersion heater 3 Calorimeter 3 Thermometer 3 Give two ways in which the heat loss from the calorimeter might have been reduced in this experiment.(7) Insulate calorimeter /use lid / use cold water (below room temperature) / polish calorimeter / low heat capacity thermometer, etc. any two Explain why using a larger mass of the liquid while supplying the same amount of energy might have produced a less accurate result. (9) Larger mass of liquid results in smaller temperature rise for a given energy 6 hence greater percentage error 3 Page 4 of 33

5 Question 3. In an experiment to verify Snell s law, a block of glass was placed on a sheet of paper. The angles of incidence, i and refraction, r for a ray of light entering the block were measured and the following results were obtained: Draw a suitable graph and explain how this verifies Snell s law. (18) Correct sin i and sin r values for eight points ( 1 per each incorrect/omitted point) 4 Label axes correctly on graph paper 3 Plot eight points correctly ( 1 per each incorrect/omitted point) 4 Straight line showing good distribution 3 Correct statement / correct equation / sin i sin r 4 From the graph, determine the refractive index of glass. (9) Correct slope method 3 n = 1.55 [range: ] 6 Using a diagram, describe how the position of the refracted ray would be determined. (7) Pins / ray box (to obtain incident and refracted rays) 3 Diagram to show: outline of block, incident and refracted ray, normal 2 Measure angle between refracted ray and normal (using a protractor / trig.) 2 Explain why placing the block on its narrowest edge would give a less accurate result. (6) Greater percentage error (in these readings) 6 Page 5 of 33

6 Question 4. The relationship between the natural frequency of a stretched string and its tension was investigated by applying force to the end of a wire of length, l. The force was varied and the resulting values of the natural frequency, f and the tension, T were determined. The following results were obtained: State the relationship between the natural frequency of the wire and its tension. (6) 1 T f T / f = 6 2l μ Using the results obtained above, draw a graph to illustrate this relationship. (6) Correct calculation of T 2 Label axes correctly 2 Plot eight points correctly 2 ( 1 for incorrectly plotted points) ( 1 for inappropriate scale) Explain how your graph verifies this relationship (6) Straight line 3 through origin 3 Given the length l was 64 cm, use the graph to calculate a value for the mass per unit length of the wire. Assume the wire was vibrating at the natural frequency. (12) 1 T f = 2l μ 3 f = T = 2l μ 3 mass per unit length (μ) = kg m 1 3 Explain how the natural frequency of the wire might have been determined. (10) Arrangement showing string, means of changing l, pulley and pan / newton balance / fixed at both ends 3 Vibrating fork placed on bridge ( 1 per item omitted) 3 Adjust length until standing wave formed / resonance occurs /rider falls off 3 Repeat with forks of different frequencies 1 Page 6 of 33

7 SECTION B (280 marks) Answer five questions from this section. Each question carries 56 marks. Question 5. Answer any eight of the following parts (a), (b), (c), etc. (a) What is the doppler effect? (7) (relative) motion 4 between source (of waves) and observer 3 (b) What is meant by the threshold of hearing? (7) It is the quietest sound an ear can detect 4 at 1,000 Hz 3 (c) Describe two methods by which white light may be dispersed. (7) Prism/Diffraction grating/raindrops. any two (d) (e) (f) When a current of 3 A is flowing in a wire, calculate the charge which passes a particular point in 5 minutes. (7) Q = It 3 Q = 3(5 60) = 900 C 4 ( 1 for omission of or incorrect units) The critical angle for light going from a certain glass to air was 45. Calculate the refractive index of this glass. (7) 1 n = 3 sin i c n = 1/0.707 = A particle is projected vertically upwards. What must the initial velocity of the particle be, if it is to rise to a height of 19.6 m? (7) 2 2 v = u + 2as 3 u = v 2 2as u = 0 2 ( 9.81)( 19.6) u = 6.2 ms 1 4 ( 1 for omission of or incorrect units) (g) What is the difference between transverse and longitudinal waves? (7) In a longitudinal wave, the motion of the medium is parallel to the direction of the wave. 4 A transverse wave is a wave in which the motion of the medium is at right angles to the direction of the wave. 3 (h) Give an example of the conversion of electrical energy to (i) kinetic energy and (ii) chemical energy. (7) (i) Electrical to kinetic eg, washing machine/ any electrical powered/battery operated device with moving parts (ii) Electrical to chemical = recharging a battery/ electrolytic cell 7 One correct (4) Page 7 of 33

8 (i) What happens when high speed electrons collide with a metal target? (7) x rays are produced 7 (j) Name the sub atomic particles that are affected by the strong force. (7) protons & neutrons (One correct, 4 marks) 7 or An OR gate has two inputs, A and B. In what circumstances will the output of the gate be high? (7) The output will be high when either A or B, or both are high 7 (One correct, 4 marks) Question 6. Define (i) displacement and (ii) acceleration. (6) (i) Displacement is the shortest distance from the initial to the final position of a point, units of m 3 (ii) Acceleration is the rate at which the velocity of a body changes with time units of ms 2 3 ( 1 for omission of or incorrect units) A body is travelling with a velocity u in a certain direction. It then accelerates uniformly in the same direction for a time t. Show that: s = ut + ½ at 2, where s is the displacement of the body and a is the acceleration. (9) Let v = velocity after acceleration u + v V average = But v = u + at V average = 2 u + u + at 2 3 V average = displacement( s) time( t) s = V average (t) s = u + u + at 2 (t) 3 s = ut + ½ at 2 3 Or it can be shown graphically using a speed time graph: 3 On a speed vs. time graph, the gradient of the line is equal to acceleration and the area under the line is equal to displacement. u multiplied by t gives the bottom rectangle of the area and v u divided by 2, gives us the top triangle. This gives us: s = ut + (v u) t/2. 3 Since v = u + at, we can rearrange to give v u = at and then substitute into the equation for displacement. This gives: s = ut + ½ at 2. 3 Page 8 of 33

9 A car accelerates uniformly from rest to a speed of 15 ms 1 in a time of 4 s. It then moves at a constant speed for the next 6 s. (i) Draw a graph showing the variation of velocity with time over the 10 seconds of motion. (6) Label axes correctly 2 Graph plotted correctly ( 1 for each incorrectly plotted point) 2 Good distribution 2 ( 1 for inappropriate scale) (ii) Calculate the total distance travelled by the car. (6) Distance = area under graph During acceleration, area of triangle = ½ base height = = 30 m 2 During constant speed, area of rectangle = L B = 6 15 = 90 m 2 Total = 120 m 2 ( 1 for omission of or incorrect units) (iii) Calculate the average speed of the car over the whole journey. (6) Total average speed = Total distance/total time m / 10 s = 12 ms 1 3 ( 1 for omission of or incorrect units) State Newton s universal law of gravitation. (6) Newton's law of gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses 3 and inversely proportional to the square of the distance between them. 3 or m1m2 F = G 2 r 6 Page 9 of 33

10 A satellite is in a circular orbit of a given radius around a planet. Show that the speed of the satellite is proportional to the square root of the mass of the planet and independent of the mass of the satellite. (8) The satellite has mass m sat orbiting the planet with mass of m p. If the satellite moves in circular motion, then the net centripetal force acting upon this orbiting satellite is given by: F net = (m sat v 2 ) / r 2 This net centripetal force is the result of the gravitational force that attracts the satellite towards the planet and can be represented as: F g = (G m sat m p ) / r 2 2 Since F g = F net, the above expressions for centripetal force and gravitational force can be set equal to each other. Thus, (m sat v 2 ) / r = (G m sat m p ) / r 2 2 v 2 = (G m p ) / r ( ) v= G m r 2 p / One of the moons of Saturn is in an orbit which has the same radius as that of the Earth s moon. Given that the speed of Saturn s moon is 10 times the speed of the Earth s moon, calculate a value for the mass of Saturn. (9) ( ) v= G mp / r v Sat moon = 10 v Earths moon 3 ( G ms) / r = 10 ( G me) / r 3 Gm s / r = 100 Gm e / r m s = 100 m e m s = kg = kg 3 ( 1 for omission of or incorrect units) Page 10 of 33

11 Question 7. Constructive interference and destructive interference take place when waves from two coherent sources meet. Explain what is meant by: constructive interference and coherent sources. (12) Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. 3 Constructive interference occurs when the phase difference between the waves is a multiple of 2π 3 Sources are said to be coherent if the waves emitted from them have the same frequency 3 and are 'phase linked'; that is, they have the same phase difference. 3 What is the condition necessary for destructive interference to take place when waves from two coherent sources meet? (6) Destructive interference occurs when the waves meet and their phase difference is an odd multiple of π 6 Describe an experiment that demonstrates the wave nature of light. (12) Diffraction grating / Young s slits // 2 polaroids 3 Spectrometer and light source / laser // light source 3 Shine light through grating or slits // shine light, rotate one 3 interference pattern // change in intensity 3 Radio waves of frequency 30 khz are received at a location 1500 km from a transmitter. The reception temporarily fades due to destructive interference between the waves travelling parallel to the ground and the waves reflected from the Earth s atmosphere as shown: (i) Calculate the wavelength of the radio waves. (6) v = fλ m / 10 km 3 (ii) (iii) What is the minimum distance the reflected wave should travel for destructive interference to occur? (9) half wavelength / 5 km km + 5 km km 3 The layer at which the waves are reflected is at a height, h above the ground. Calculate the minimum height of this layer for destructive interference to occur at the receiver. (11) Pythagoras theorem (any implication) 3 Substitution 3 61 km // m 5 ( 1 for omission of or incorrect units) Page 11 of 33

12 Question 8. Define simple harmonic motion. (6) Simple harmonic motion is a type of periodic motion 3 where the restoring force is directly proportional to the displacement 3 State Hooke's Law. (6) The force F needed to extend or compress a spring by some distance x 3 is proportional to that distance 3 // F = kx A spiral spring has a length of 1 m. A mass of 0.5 kg is attached to the end of the spring and is allowed to hang freely. The length of the spring becomes 1.2 m. Find the constant for the spring. (6) F = kx 2 F = mg = = 4.9 N 2 4.9/0.2 = 24.5 Nm 1 2 ( 1 for omission of or incorrect units) The mass is then pulled down a further distance x and then released. What is the resultant force, in terms of x, acting on it? (6) The resultant force is a restoring force of: F = kx = 24.5x 6 Show that the mass executes simple harmonic motion. (6) F = ma ma = kx 2 a = (k/m) x 2 a s 2 acceleration proportional to displacement / ( ) Calculate the period of the motion. (6) 2π T = ω 2 ω = k m 2 2 π T = = 0.89 s 7 2 State the principle of conservation of energy. (6) The law of conservation of energy states that the total energy of a system cannot change it is said to be constant over time. Energy can be neither created nor destroyed, but can change from one form to another 6 A simple pendulum has a length of 85 cm. The maximum angular displacement of the pendulum is 35. Use the principle of conservation of energy to calculate the maximum speed of the pendulum bob. (9) PE = KE 3 PE (due to displacement of height 0.15 m) = mgh = m b = 1.47m b 3 PE = ½ m b v 2 = 1.47m b v = 1.72 ms 1 3 ( 1 for omission of or incorrect units) Explain why the motion of the pendulum should not be considered to be simple harmonic. (5) The motion of the pendulum is simple harmonic only when θ is small (< 5 o ), ie sin θ θ 5 Page 12 of 33

13 Question 9. Define specific latent heat. (6) The specific latent heat of a substance is the amount of heat required to convert one unit mass/1 kg of a substance, from one state to another 3 without a change in temperature 3 Describe an experiment to measure the specific latent heat of fusion of ice. (15) Correct apparatus e.g. Ice, water, calorimeter, lagging, beakers, kitchen paper, digital thermometer and electronic balance. 5 Correct procedure 5 Correct calculation Conduction, convection and radiation are three methods of heat transfer. Give an explanation of each. (9) Conduction is the transfer of heat energy by diffusion and collisions of particles within a body due to a temperature gradient 3 Convection, is the transfer of heat from one place to another by the movement of fluids 3 Radiation is the transfer of heat by electromagnetic waves. No particles are involved 3 Explain the principles involved in each of the following: (i) The u valve of a structure is reduced by adding insulation to it. (6) U value measures heat / energy loss. 3 Heat loss is reduced 3 (ii) On a hot day, the sea is usually colder than the land. (6) Specific heat capacity is greater 3 for water than for land 3 (iii) The human body is cooled by perspiring. (7) Evaporation 4 removes heat 3 5 (iv) On a hot day, the water on the surface of a still lake or pond is usually warmer than the water some distance below the surface. (7) Conduction is poor / convection currents go up not down / warm water is less dense and does not sink 7 Page 13 of 33

14 Question 10. Answer either part (a) or part (b). (a) In 1932 the English physicist, John Cockroft and the Irish physicist, Ernest Walton, bombarded lithium with protons. 7 1 Complete the equation: Li+... (6) 3 1H Li + 1He 2He+ 2He + Energy 2 marks each Describe, with the aid of a diagram how this experiment was carried out. (12) Proton source 3 Accelerator 3 Lithium target 3 Zinc sulphide screens & microscope 3 What is the historical significance of this experiment? (6) This was the first artificial splitting of a nucleus 3 This reaction was the first experimental proof of Einstein's E = mc 2 3 If the mass of the lithium nucleus is kg, the mass of the proton is kg and the mass of an alpha particle is kg, find the energy produced. (12) (Speed of light, c = m s 1 ) Mass difference = ( ) = Kg E = mc 2 E = ( ) 2 = J Give the number of quarks and type of quarks in the composition of: (i) baryons (3) Three uds (ii) mesons (3) Two udsc In terms of u (up) and d (down) quarks and u and d anti quarks, give the composition of any named baryon and meson. (14) Baryon = Proton; uud or neutron; ddu any correct baryon 4; composition 3 Meson = Pion; u d any correct meson 4; composition 3 Page 14 of 33

15 (b) OR Describe an experiment to show that a current carrying conductor in a magnetic field experiences a force. (8) A strip of aluminium foil is placed at right angles to a U shaped magnet. The foil is connected in series with a battery and a switch. 4 When the switch is closed the aluminium foil experiences an upward force. 4 Draw a labelled diagram of a simple D.C. motor and explain how it works. (21) Diagram 9 The conductor in the shape of a coil is connected to a split ring commutator. 4 The conductor is then manually rotated in the magnetic field generating an emf in accordance with Faraday's Law of electromagnetic induction. 4 The split ring commutator accommodates the change in direction of the current in the loop, thus creating direct current (DC) current going through the brushes and out to the circuit. 4 Page 15 of 33

16 Explain how such a motor could be converted to an A.C. generator. (9) In an AC generator the two ends of the coil are each attached to a slip ring that makes contact with brushes as the coil turns. 6 The two slip rings of the AC generator allow the coil to turn without breaking the connections to the load circuit. 3 Sketch a graph to show how the E.M.F. generated would vary with time and give the relationship between the peak value and the R.M.S. value. (9) 3 rms = a, a = amplitude/peak value 2 6 In a car an A.C. generator is used to recharge the battery. The figure shown is a simple circuit which could be used for this purpose. Name the component which could be connected between A and B in the diagram. (6) Diode 6 Draw the correct symbol for this component. (3) 3 Page 16 of 33

17 Question 11. Read the following extract and answer the questions below. The explanation of the photoelectric effect was the major work cited in the award to Albert Einstein of the Nobel Prize in Physics in Einstein s theory, proposed in 1905, played a major role in the development of atomic physics. Not only were most of the experimental details still unknown in 1905, but the key point of Einstein s explanation was contrary to classical ideas of the time. (The project Physics Course, Halt, Rinechant and Wilson, New York) (a) What is the photoelectric effect? (7) The photoelectric effect is the emission of electrons from a material 4 upon the absorption of electromagnetic radiation of suitable wavelength 3 (b) Give an expression for Einstein s photoelectric law. (7) E max = hf ϕ Partly correct 4, fully correct 7 (c) Draw a labelled diagram of a photocell. (7) Diagram 4, correct labelling 3 (d) How could the light intensity falling on the cell be varied? (7) Set us as shown in diagram, bring the light source closer to the photocell, 4 light intensity increases 3 (e) What is the relationship between the intensity of the light and the photocurrent? (7) Current is directly proportional to 4 Intensity 3 (f) Mention two practical applications of a photoelectric cell. (7) Controlling the flame in central heating boilers / automatic doors / fire alarms / photocopiers / light meters, etc. Any two 7 When radiation of wavelength m falls on a metal surface, the maximum kinetic energy of the emitted electrons is found to be 4.2 ev. What is the value of: (g) the work function of the metal in joules? (7) hf = φ + ½mv 2 hf ½mv 2 = φ ( ) J 1 ( 1 for omission of or incorrect units) (h) the threshold frequency for the metal? (7) hf 0 = φ 3 f 0 = φ /h = J/ Js Hz 1 ( 1 for omission of or incorrect units) Page 17 of 33

18 Question 12. Answer any two of the following parts (a), (b), (c), (d). (a) Define capacitance. (6) The ability of a system to store 3 an electric charge/ energy 3 Mention two common uses of capacitors. (6) Traditional radio receivers/motor starters/noise filter/storing energy etc. Any two 6 A parallel plate capacitor has two square plates of side 12 cm, which are 3 mm apart. Calculate the capacitance of the capacitor and calculate the energy stored in the capacitor when the potential difference between the plates is 180 V. (16) C = ε 0 A/d (0.0144/0.003) F 2 E = ½ CV 2 3 ½ J / 696 nj 2 ( 1 for omission of or incorrect units) (b) Distinguish between nuclear fission and nuclear fusion. (9) Fission is a radioactive decay process in which the nucleus of a particle splits into smaller parts (lighter nuclei) and releases a very large amount of energy. Fusion is a nuclear reaction in which two or more atomic nuclei collide and join to form a new type of atomic nucleus with the release of large amounts of energy. (One correct 6, both correct 9) 9 Complete the following nuclear reaction by replacing X with the appropriate symbol. (9) X 1 ( n) 0 U N = Cs + Rb + X Energy = 2 9 Given that the masses of the uranium, caesium and rubidium nuclei are u, u and u, respectively and the mass of the neutron is u, calculate in joules, the energy given off on the right hand side of the equation. (10) Mass of LHS = Mass of RHS = (one neutron cancel from both sides) 2 ΔM = u = kg 2 Binding energy = mc 2 = kg ( m s 1 ) 2 2 E = J 2 ( 1 for omission of or incorrect units) Page 18 of 33

19 (c) Describe an experiment to show the wave nature of sound. (9) Walking slowly from X to Y, you will notice the loudness of the sound increasing and decreasing at regular intervals. 3 This is because sound waves from the two speakers will interfere both constructively and destructively, along the path XY. 3 Explain the terms stationary (standing) wave and harmonics. (6) A standing wave is a wave that remains in a constant position 3 A harmonic of a wave is a wave with a frequency that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, etc. 3 A stationary wave is set up between a loudspeaker which is emitting a note of 1500 Hz, and a wall. If the distance between the first and eleventh node is 112 cm, calculate the velocity of the sound. (13) The distance between the first and eleventh node is equal to 5 wavelengths 3 5λ = 1.12 m 3 λ = m 3 f = v/ λ 3 v = f λ = ms 1 1 ( 1 for omission of or incorrect units) (d) State Coulomb s law of forces between electric charges. (6) Coulomb's law states that the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects 3 and inversely proportional to the square of the separation distance between the two objects. 3 Q1Q 2 F = k 2 r Define electric field strength and state the unit in which it is measured. (6) The strength or intensity of an electric field at any point 3 Newton/Coulomb / N/C 3 Use Coulomb s law to derive an expression for the electric field strength at a distance r from a point charge Q. (9) Q1Q 2 F = k 2 r Electric field strength = Force / Charge = F/Q 3 Electric field strength = F/Q = kqq / Q r 2 3 = kq/r 2 Electric field strength = kq 2 r 3 3 Page 19 of 33

20 Calculate the magnitude of the electric field strength at a point which is 5 cm from a positive charge of 2 μc. (7) k = Nm 2 /C 3 r = 0.05 m q = 2 μc electric field strength = μc / (0.05) NC 1 1 ( 1 for omission of or incorrect units) Page 20 of 33

21 ORDINARY LEVEL Section A (120 marks) Three questions to be answered from this section. Question 1 40 marks The momentum of a body is given by the formula ρ = mv. (i) What does the symbol v stand for? (3) Velocity/speed 3 (ii) Draw a labelled diagram showing how you would verify the principle of conservation of momentum. (12) Correctly labelled 6 Constant velocity; hence incline 6 (iii) What measurements do you record during this experiment? (9) Weight of each trolley using an electronic balance / weighing scales. 3 Measure distance, time 3 Momentum = mass velocity 3 (iv) How do you get a value for v from the measurements you took? (9) Ticker tape timer method: Time between dots = 0.02 secs 3 We measured the distance for a particular number of intervals 3 Velocity = distance time 3 Using a data logger: Select an appropriate set of points on a distance vs. time graph Use the slope tool to give the velocity (v) How would you know that the principle of conservation of momentum was verified? (7) Upon repeating the experiment a number of times, 4 the value for momentum before and after was always the same (within the limits of the experimental error) 3 Page 21 of 33

22 Question 2 40 marks The diagram shows a circuit used by a student to investigate the variation of current with potential difference for a metallic conductor. (i) Name the parts of the apparatus labelled A, X and Y. (9) X = voltmeter 3 A = ammeter 3 Y = Rheostat / (variable) resistor / potential divider / potentiometer 3 (ii) What does X measure? (3) X measures volts 3 (iii) Describe how the part labelled Y was used in the experiment. (6) Y changes the resistance / voltage / current The following table shows the values recorded for the current I and the potential difference V during the experiment. (iv) Using the data, draw a graph on graph paper of I against V. (12) Label axes correctly 4 Plot nine points correctly ( 1 for incorrectly plotted points) 4 Good distribution 4 (iv) From your graph, calculate the resistance of the conductor. (Hint: V = IR) (10) Straight line drawn through origin 4 Correct slope calculation Ω // value consistent with the graph 2 (partial answer e.g. evidence of using the graph, (5)) Page 22 of 33

23 Question 3 40 marks In an experiment to measure the speed of sound in air, a student found the frequency and the wavelength of a sound wave. (i) Draw a labelled diagram of the apparatus used in the experiment. (12) Labelled diagram to show: air column / resonance tube // CRO 3 frequency source e.g. tuning fork / signal generator 3 metre stick stated or implied // microphone 3 method of varying (the air column) length / frequency // reflecting surface 3 ( 1 for no labels) (ii) Describe how the student found the wavelength of the sound wave. (9) Over the resonance tube, hold the vibrating tuning fork / speaker 3 Adjust the length of the air column until resonance occurs 3 λ = 4 length of air column 3 (If the student measures the length of the air column but makes no reference to its relationship with λ give (2) marks only) Accept valid alternatives A labelled diagram may merit marks (iii) How did the student find the frequency of the sound wave? (6) (read it) from the tuning fork / signal generator / used tuning forks of known frequency 6 (iv) State one difference between light waves and sound waves. (6) Sound waves are longitudinal waves 3 while light waves are transverse waves 3 (v) What is an ultrasonic wave? (3) An ultrasonic wave is a wave with a frequency greater than the upper limit of the human hearing range 3 (vi) Give one precaution that the student took to get an accurate result. (4) Repeated using different frequencies (and took an average), end correction, (took measurements from the) sharpest resonance etc. any one 4 (Partial answer e.g. repeat / average, (2)) Page 23 of 33

24 Question 4 40 marks You carried out an experiment to measure the focal length of a converging lens. (i) Draw a labelled diagram of the apparatus that you used in the experiment. (12) converging lens 6 object e.g. pin, raybox, crosswires, slit, bulb (filament) screen // pin for no parallax metre stick Any two lines 6 ( 2 for no labels) (ii) Describe how you found the position of the image formed by the lens. (6) moved the screen/object /lens 3 until there was a clear image // no parallax 3 (partial answer e.g. reference to movement, (3)) (iii) What measurements did you take? (9) Distance from object to the lens // u Distance from the screen/ image to the lens // v two correct (any one (6)) The table shows the measurements recorded by you: Using the formula or otherwise and the above data, find an average value for the focal length f of the lens. (13) = + f u v 1/20 + 1/64 = 1/f f = 15.2 cm 4 1/30 + 1/43 = 1/f f = cm 2 1/40 + 1/41 = 1/f f = cm 2 1/50 + 1/35 = 1/f f = cm 2 Average = cm 3 Page 24 of 33

25 SECTION B (280 Marks) Five questions to be answered in this section. Question 5 any eight parts Take the best 8 from 10 parts 56 marks (a) A person whose weight is 700 N enters a lift at the ground floor. The lift rises 10 m to the third floor. Calculate the work done on the person. (W = Fs) (7) F = 700 N, s = 10m W = Nm 3 (b) Why is frost unlikely on a cloudy winter s night? (7) Frosts usually occur during winter nights when energy from the sun is not available to heat the surface. 3 On cloudy nights, cloud can act as a 'blanket'/insulator and trap warm air near the surface meaning frost formation is unlikely. 4 (c) Convert 27 C to Kelvin. (7) K 7 (d) What physical quantity is measured in decibels? (7) Sound pressure level / loudness 7 (e) What is the colour of the live wire in an electric cable? (7) Brown 7 (f) Give one use for a semiconductor diode. (7) Allow current flow 4 in one direction 3 (g) Which atomic particle was named by the Irish scientist G. J. Stoney? (7) Electron 7 (h) State two properties of x rays. (7) Electromagnetic waves/ travel in straight lines/ They cannot be reflected, refracted or deflected by magnetic or electric fields/ interact with materials they penetrate and cause ionization etc (i) Name a radioactive isotope used in finding the age of an object. (7) Carbon 14 / any other valid isotope eg. uranium (j) Give an example of the doppler effect. (7) When a car, train or bus passes you and the sound is loud, this is when the waves are compressed meaning the object is moving towards you, 4 whilst when it moves away the sound dies down and the wavelength length increases meaning the object is moving away 3 Page 25 of 33

26 Question 6 56 marks (a) (b) Copy this statement of Newton s final law of motion into your answer book and complete it: An object remains at rest or moves with constant speed in a straight line unless... (9) A resultant external force 6 acts upon it 3 A car of mass 1200 kg was travelling at a constant speed along a level road. Draw a diagram showing two of the forces acting on the car. (8) Weight / resultant / frictional force. Any two The car hit a wall at a speed of 20 m s 1 and was stopped in 0.2 s. Calculate: (i) The acceleration of the car during the collision. (9) v = u + at 3 a = v u/t = 20/0.2 3 = 100 ms 1 3 ( 1 for no sign or incorrect units) (ii) The resultant force acting on the car during the collision. (6) F = ma x N 3 ( 1 for no sign or incorrect units) (iii) The energy of the car just before it hits the wall. (6) E = 1/2mv 2 3 = J 3 (c) The driver was not wearing a seat belt and hit the steering wheel when the car was suddenly stopped in the collision. Explain why the driver hit the steering wheel during the collision. Refer to Newton s first law of motion in your answer. (9) Moving objects have momentum. 6 Newton's First Law of Motion says that unless an outside force acts on the driver, the driver will continue to move at its present speed and direction and hit the steering wheel. 3 (d) How could wearing a seat belt have prevented the driver hitting the steering wheel? (6) If the passenger is restrained by a seat belt, their momentum is reduced 3 more gradually by the constant and smaller force of the belt acting over a longer period of time. 3 (e) Name one other safety feature in cars. (3) Airbags / antilock brakes 3 Page 26 of 33

27 Question 7 56 marks (i) What is meant by temperature? (6) The degree of hotness or coldness of a body 6 (ii) Heat can be transferred by conduction. Name two other ways of transferring heat. (6) Convection 3 Radiation 3 (iii) Describe an experiment to show how different solids conduct heat at different rates. (15) Apparatus: a number of different metal rods, 3 Heat source 4 Procedure: heat all the ends of the rods at the same time, rods same length and same thickness, other valid detail 4 Observation/conclusion: e.g. wax melts on (different) rods at different times, (different) rods conduct heat at different rates 4 Accept valid alternatives A labelled diagram may merit marks (iv) The spongy material in a wet suit contains trapped air that keeps the layer of water near a swimmer s skin from moving. Explain how the trapped air can keep a swimmer warm. (6) Air is a poor conductor/good insulator 3 Reduces heat loss from divers body 3 (v) Explain how the layer of water can keep a swimmer warm. (6) Swimmer rapidly heats up the thin layer of water trapped against their body to nearly body temp. 3 The warm layer of body temperature water conducts less heat away from the diver than the cooler surrounding water 3 (vi) A vacuum flask (thermos flask) is designed to keep a liquid at constant temperature by preventing energy entering or leaving the flask. With reference to the diagram, explain how the flask prevents energy entering or leaving the flask. (17) The vacuum prevents conduction 5 The tight stopper prevents air from entering or leaving the flask, so convection isn't possible. 6 When infrared radiation tries to leave the hot liquid, the reflective lining of the inner chamber reflects it straight back in again 6 Page 27 of 33

28 Question 8 56 marks (i) Describe an experiment to show the heating effect of an electric current. (12) Apparatus: source e.g. power supply 3 conductor e.g. bulb, wire 3 Procedure: set up the circuit / allow current to flow 3 Observation/conclusion: wire gets hot 3 Accept valid alternatives A labelled diagram may merit marks The diagram shows part of a lighting circuit: (ii) A is a 75 W lamp. Calculate the current flowing through lamp A when the switch is closed. (12) P = IV 6 I = P/V = 75/230 = 0.33 A 6 (iii) At the same time, the current flowing through the fuse is 0.76 A. What is the current flowing through lamp B? (6) I = I A + I B = I B = 0.43 A 3 (iv) Calculate the power generated in lamp B. (9) P = IV 3 P = = 99 W 6 (v) Explain how a fuse acts as a safety device in an electrical circuit. (6) Fuse consists of thin piece of wire 2 If current is too high 2 Wire melts and circuit is broken 2 (vi) An electric kettle is rated 3 kw. The kettle is switched on for 30 minutes each day. How many units of electricity does the kettle use each day? (6) Number of kilowatt hours = Number of kilowatts Number of Hours 2 Number of kilowatt hours = 3 kw 0.5h = 1.5 kwh kwh = 1.5 Units 2 (vii) How much does it cost to use the kettle each day when one unit of electricity costs 15 cent? (5) cent = 22.5 cents 5 Page 28 of 33

29 Question 9 56 marks (i) What is the difference between a permanent magnet and an electromagnet? (6) In an electromagnet the magnetic field is created through electric current in a wire wound coil and strengthened by a soft iron core. As soon as you turn off the power, the soft iron core loses its magnetisation. 3 A permanent magnet is made of ferromagnetic material 3 (ii) (iii) (iv) Magnets have many uses in the home. Give one use in the home of (i) a permanent magnet (ii) an electromagnet. (6) A permanent magnet = fridge magnet / fridge doors/ speakers 3 An electromagnet = all motors eg. vacuum cleaner etc. 3 The needle of a magnetic compass is a permanent magnet. Explain why a nearby electric current causes a compass needle to move. (9) The flow of current produces a magnetic field around it 6 This magnetic field interferes with the magnetic field of the compass moving the needle 3 A solenoid (long coil of wire) is connected to a cell as shown. Copy this diagram into your answer book and draw the magnetic field around the solenoid. (9) Uniform field in the centre 3 Weak field outside 3 Correct direction of N/S pole 3 (v) Explain the term electromagnetic induction. (9) Electromagnetic induction is the production of a potential difference (voltage) 3 across a conductor when it is exposed to a varying 3 magnetic field 3 (vi) A magnet and a coil of wire can be used to produce electricity. Describe with the aid of a diagram how to show this. (17) Galvanometer 3 Magnet 3 Long coil of wire 3 Correctly labelled diagram 2 Move magnet in and out of coil 3 Observe flow of current using galvanometer 3 Page 29 of 33

30 Question marks Alpha, beta and gamma (α, β, γ) are three types of radiation. Match each of the following descriptions with the correct type of radiation: (9) (i) Short wavelength electromagnetic radiation. γ 3 (ii) A particle consisting of two protons and two neutrons. α 3 (iii) A fast moving electron. β 3 Radon 222 is a radioactive gas that can seep into buildings from underground rocks. It undergoes the following nuclear reaction: (iv) What type of radiation is emitted by radon 222? (6) 4 Alpha / He 2 6 (v) What is a possible effect on your health caused by high levels of radon gas? (5) Lung cancer 5 (vi) Explain what is meant by the half life of a radioactive material. (6) A half life is the time it takes for half the original quantity 3 of a given radioisotope to decay 3 (vii) The half life of radon 222 is 4 days. The activity of a sample of radon 222 is measured as 520 Bq. Estimate the activity of the sample after 8 days. (9) Day 0 = 520 Bq Day 4 = 520/2 = 260 Bq 6 Day 8 = 260 / 2 = 130 Bq 3 (viii) What is the principle on which a detector of ionising radiation works? (9) As radiation passes through air or a specific gas, ionization of the molecules occur. 6 When a voltage is placed between two areas of the gas filled space, a current will flow and be detected 3 (ix) Which has the most penetrating power, α, β or γ? (6) Gamma 6 (x) How would you compare the penetrating powers of the three types of radiation? (6) Gamma radiation can travel many feet in air and many inches in human tissue. They are the most penetrating radiation. 2 Beta radiation may travel several feet in air and is moderately penetrating. 2 Alpha radiation is not able to penetrate human skin; it is the least penetrating 2 Page 30 of 33

31 Question 11 Read the following passage and answer the accompanying questions. 56 marks Forty of every hundred workers who have worked all their lives at high noise levels (90 db) will, at the age of 65 years, find it difficult to hear other people talking. Some of these workers will even be deaf. If you are exposed to continuous loud noise at work there are rules your employer must follow to protect you from noise exposure. They must assess, measure and control noise and supply hearing protection as appropriate. The level of noise to note is 85 db. If it is necessary to communicate by shouting at a distance of 2 m, the noise level may be greater than 85 db. (a) What is noise? (7) Noise is unwanted / irregular sound 7 (b) What must employers do if their workers are exposed to high noise levels? (7) They must assess, measure and control noise and supply hearing protection 7 (c) How might a person s hearing be affected by exposure to high noise levels? (7) Difficult to hear 4 May become deaf 3 (d) Name a job where a worker might experience a high noise level. (7) Rock musicians /airport ground staff / industrial manufacturing factory etc. 7 (e) What unit is used to measure noise levels? (7) Decibels 7 (f) How can an employee know if there is a problem with noise levels? (7) If it is necessary to communicate by shouting at a distance of 2 m 7 (g) Name an instrument to measure noise levels. (7) Sound level meter 7 (h) Where else, other than at work, might you be exposed to high noise levels? (7) Concerts / beside airport runways etc. 7 Page 31 of 33

32 Question marks Answer any two of the following (a), (b), (c) and (d). (a) (i) State Boyle s law. (9) The absolute pressure exerted by a given mass of an ideal gas 3 is inversely proportional to the volume it occupies 3 if the temperature and amount of gas remain unchanged within a closed system 3 P 1 V (ii) Describe an experiment to show that pressure in a liquid increases with depth. (12) Get a large plastic bottle with a series of holes in the side one above the other. 4 Cover the holes with sticky tape and then fill the container with water. 4 Now remove the tape. The water comes out faster from the holes nearer the bottom where the water is deeper and so the pressure of the water is greater. 4 (iii) An air bubble rises from the bottom of a river. The volume of the air bubble is 20 mm 3 at the bottom of the river, where the pressure is 300 kpa. What is the volume of the air bubble near the surface of the water where the pressure is 100 kpa? (7) PV = constant P 1 V 1 = P 2 V = 100 V 2 V = / V = 60 mm 3 1 (b) (i) White light is made up of light of different colours. How would you show this? (9) White light source 3 Prism / grating 3 Screen / telescope 3 (ii) Sunlight contains radiations that the human eye cannot see. Name two of these radiations. (6) Any two; radio, x ray, microwave, IR, UV (iii) Describe how to detect one of these radiations. (9) IR detected as heat / UV detected by sun burn / X ray detected by photography and the GM tube etc. 9 (iv) Give one use of this radiation. (4) Any valid use 4 Page 32 of 33

33 (c) (i) Describe, with the aid of a diagram, an experiment to show that a force exists between electric charges. (12) A balloon is charged by rubbing it with hair. It is then brought near some bits of paper. The charged balloon attracts the paper bits, lifting them up off the table. This demonstrates the attraction between charged objects and neutral objects. Any correct diagram 6 Correct explanation 6 (ii) What is meant by point discharge? (6) The electric field strength is greater around a pointed object. 3 The intense electric fields surrounding a pointed object serve to ionize the surrounding air, thus enhancing its conductive ability. 3 (iii) A lightning conductor is made from a thick copper strip. One end is pointed and the other end is put into the ground. Explain how a lightning conductor protects a building from being damaged by lightning. (10) During electrical storms, huge amounts of electric charge are separated in clouds. Charges near the bottom of clouds induce equally large charges in the earth beneath, on trees and on buildings. 5 When the accumulated voltage is high enough, a discharge occurs, either within the cloud or between the cloud and the earth. A lightning conductor is usually made of thick copper and is buried deeply in the earth as this provides a low resistance path for any flow of electric charge between the earth and the atmosphere. 5 (d) (i) What are x rays? (6) an electromagnetic wave of 3 high energy and very short wavelength 3 (ii) The diagram shows an x ray tube. Name the parts labelled A, B and C. (9) B = Anode 3 A = cathode 3 C = window 3 (iii) Explain what happens at A. (6) A is a filament which is heated. 3 It emits electrons due to thermionic emission 3 (iv) Give two uses of x rays. (7) Photographs (radiographs) of the body for medical diagnosis In industry, it is used for non destructive testing of products for defects Any two valid uses Page 33 of 33

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