PRE-LEAVING CERTIFICATE EXAMINATION, 2011 MARKING SCHEME PHYSICS HIGHER AND ORDINARY LEVEL

Transcription

1 *WMS1* PRE-LEAVING CERTIFICATE EXAMINATION, 011 MARKING SCHEME PHYSICS HIGHER AND ORDINARY LEVEL 5 Finglas Business Park, Tolka Valley Road, Finglas, Dublin 11 T: , F: , E: info@examcraft.ie, W: Page 1 of 9

2 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.. Words, expressions or statements separated by a solidus, /, are alternatives which are equally acceptable.. 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.. 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 of 9

3 HIGHER LEVEL 1. In an experiment to verify the principle of the conservation of momentum a student wrote. I measured the mass m 1 of trolley 1 and the mass m of trolley. I measured the distance s 1 travelled by trolley 1 for 0. seconds before it collided with trolley. The trolleys stuck together as a result of the collision. I then measured the distance s travelled by the combination for 0. seconds immediately after the collision. The student recorded the following data: Attempt m / g m / g s / cm s / cm 1 1 First Second third Draw and label a diagram of the experimental arrangement. () Diagram to include trolleys Method of joining together Method for measuring distance / time ticker tape timer or data logger any two for all How might the student ensure the trolleys join together as a result of the collision. () Magnets / pin and cork / Velcro / any correct idea Using the data above show how the conservation of momentum was verified. (18) First attempt u = = 0.75ms 1 v= = 0.8ms = = 0.19 verified within acceptable experimental limits Second attempt u = = 0.8ms 1 v= = 0.55ms = = verified within acceptable experimental limits Third attempt u = = 0.975ms 1 v= = 0.49 ms = = 0.49 verified within acceptable experimental limits The distances measured correspond to a time interval of 0. seconds. How might this time interval be measured. (7) Reference to time associated with 10 spaces on a strip of ticker tape 7 Any other correct idea Give two precautions that the student might take to improve the accuracy of the experiment. () Polish table/ keep table horizontal/ etc any two for marks each Page of 9

4 . In an experiment to measure the specific heat capacity of a liquid a quantity of the liquid was heated electrically in a copper calorimeter. The energy supplied was measured with a joulemeter. The following measurements were obtained Mass of calorimeter Mass of calorimeter and liquid Initial temperature of liquid and calorimeter Final temperature of liquid and calorimeter Electrical energy supplied 8 g 75.5 g 15 0 C 0 0 C 00 J Using these measurements calculate the specific heat capacity of the liquid given that 1 1 the specific heat capacity of copper is 90 Jkg K (18) energy = mcδ θ + mcδ θ 00 = c = 0.75 c = 0.75 c Jkg K = c answer + units + Draw and label a diagram of the experimental arrangement. (9) Calorimeter Liquid Thermometer Energy supply Lagging etc any three If a joulemeter was not available how would the electrical energy supplied be measured. () Voltmeter and ammeter and timer all three for One missing - Explain why the rise in temperature is the least accurate quantity measured in the experiment and state how the accuracy of this measurement could be improved. (7) Rise in temp only given to one significant figure 4 More sensitive thermometer/ larger rise. Page 4 of 9

5 . In a laboratory experiment to measure the speed of sound in air a student sounded a tuning fork of known frequency above the open end of a hollow glass tube. The tube was submerged in a tall graduated cylinder of water. The tube was adjusted in the water until resonance was found. The length of the tube above the water level was measured and recorded. The procedure was repeated with several tuning forks. The internal diameter of the tube was measured as cm. The following data were obtained. Frequency / Hz Length of tube / cm Draw and label a diagram of the experimental arrangement. () Glass tube Graduated cylinder Tuning fork all three for One missing How did the student detect resonance in this experiment? () Sound was louder How did the student ensure that the resonance detected was the first position of resonance? () start with tube fully immersed and rise slowly By drawing a suitable graph on graph paper show how the relationship between frequency and wavelength could be illustrated What is this relationship? By using the graph calculate a value for the speed of sound in air. (1) frequency L+d / cm λ / m λ 1 m Page 5 of 9

6 points + label axes + good line ++ = 1 The relationship is frequency is inversely proportional to wavelength Speed of sound = slope = y y = = = ms x x The student decided to repeat the experiment with a set of tuning forks of much higher frequencies than those listed in the table above. Explain why this would result in a less accurate value for the speed of sound in air. (7) Higher frequency smaller wavelength smaller lengths measured less accuracy 7 4. Joule s law was verified experimentally by passing an electric current through a heating coil in a plastic calorimeter containing water. The rise in temperature Δ θ was measured for a series of values of the current I. The time for which the current flowed in each case was minutes. The following data was collected: I / A Δθ / C Draw and label a diagram of the experimental arrangement. (9) Plastic calorimeter Heating coil Thermometer Ammeter Energy supply Timer all six for 9 for each missing (no negative mark!!) Use the above data to draw a suitable graph on graph paper and show how this graph verifies Joule s law. (1) I / A Δθ / C Page of 9

7 points + label + good line ++1 = 9 Straight line through the origin verifies that temp rise is proportional to current squared The resistance of the heating coil was 8 Ω. The specific heat capacity of the 1 1 water was 4180 Jkg K. Assuming that all the electrical energy supplied was absorbed by the water use the graph to calculate the mass of water in the calorimeter. (1) Energy supplied = heat gain of water I Rt = mcδ θ I R t Δθ c = m 1 slope = m = m kg = m The largest value for a rise in temperature in the above table is 9. 0 C. What problem would arise with a value of temperature rise greater than this value. (7) Higher temp rises would result in large heat loss to the surrounding air 4 Less accurate result Page 7 of 9

8 5. Answer any eight of the following parts (a), (b), (c) etc. (a) The earth spins about an axis through the geographical poles once every day. Using this information calculate the angular speed of this spin. (7) π π ω = = = T rad s 5 1 (b) State Boyle s law for gases. (7) Correct statement 7 7 (c) State two factors on which the natural frequency of a stretched string depend. (7) Length / tension / mass per unit length any two 4 + (d) Name two uses for a convex mirror (7) Rear mirror in car / security mirror etc. 4 + (e) (f) Michael Faraday once shocked a live audience by standing inside a metal cage which was charged to a very high voltage. He was unharmed. What principle of physics was illustrated by this. (7) No electric field inside a hollow metal charged conductor 7 Calculate the total resistance between points A and B in the circuit illustrated by the diagram below. (7) 10Ω 10Ω A 10Ω 10Ω B Two 10 in parallel give = 10 ohms in total (g) Name two thermometric properties. (7) Length of mercury column / emf thermocouple / resistance etc 4 + (h) (i) (j) 7 1 Calculate the force on an electron travelling at 10 ms in a magnetic field 19 of magnetic flux density 4 T. ( charge on electron = C ) (7) F B qv = = 10 = N 7 Beta particles are more penetrating than alpha particles. Explain in terms of ionisation why this is so. (7) Beta are less ionising 7 Name the Irish scientist who shared the Nobel prize with J. D. Cockcroft in E T S Walton 7 OR Name the irish scientist who invented an induction coilin the 19 th century. (7) N. Callan 7 Page 8 of 9

9 . State Newton s three laws of motion (9) Correct statement + + Explain clearly the difference between weight and mass and calculate the weight of a mass of 50 grams. (9) Weight = pull of earth s gravity Mass = quantity of matter Weight = =.4 N A person of mass 7 kg stands on the floor of an elevator. Calculate the force the floor of the elevator exerts on the person when. (i) the elevator is ascending with a uniform speed F = m g = = 705. N 9 (ii) the elevator is descending with an acceleration of.5ms (18) F mg = ma F = 7.5 F = 885. N 9 If the support cable snaps the elevator would be in free fall. Show mathematically why the person would experience weightlessness. (9) F mg = ma F = F = 0 9 The astronauts on board the International Space station experience weightlessness even though the value of the acceleration due to gravity at that altitude is approximately 8.7 ms. Explain how this is so and comment on how the prolonged experience of weightlessness can cause problems for astronauts. (11) The astronauts and the ISS are in free fall 5 Prolonged weightlessness means muscle not being used means muscle wastage Page 9 of 9

10 7. State the laws of refraction. () Usual statement + Draw a ray diagram to show the formation of a virtual image with a converging lens. (1) Usual diagram label object and image Two rays Correct position of object and image The image formed in a converging lens of focal length 1 cm is twice the size of the object. Calculate the positions of the object for this to happen. (1) v magnification = = v = u u Real image Virtual image = u u = u 1 48 = u 4 cm = u = u u 1 1 = u 8 cm = u Explain why a diverging lens can not be used as a magnifying glass. (5) Image in a diverging lens is always diminished 5 if always missing Draw and label a diagram of the human eye. Name two common defects of the human eye and state clearly the type of lens used to correct each defect. (1) Usual diagram lens, cornea, iris, retina, pupil 9 ( for each missing) No negative mark!! Short sightedness diverging lens + Long sightedness converging lens + Page 10 of 9

11 8. Define capacitance and potential difference. () Usual definition + Name the three factors on which the capacitance of a parallel plate capacitor depends. Common area, permittivity of dielectric, distance between plates ++ Outline a demonstration experiment to verify one of the factors that you named. (14) Diagram of capacitor and multimeter to read capacitance 4 Larger distance smaller capacitance Or Larger permittivity larger capacitance Or Larger area larger capacitance 4 Give two uses of capacitors in electrical circuits. () Tuning a radio, smoothing output from a rectifier + In the circuit diagram below a 5. kω resistor in connected in series with a 0 μ F capacitor, a 1V battery and a switch. After closing the switch the current flowing for an instant was 0.9 ma. When the capacitor was fully charged the current flowing was zero. 1 V 0 μf 5. kω Calculate (i) the potential difference across the resistor for the instant that the current was 0.9 ma V = IR= = 5.04V (ii) (iii) (iv) the potential difference across the capacitor for this same instant V = =.9 V the charge on the capacitor for this same instant 4 Q = C V = = Coulomb the charge on the capacitor when it is fully charged 4 Q = C V = = C (v) the energy stored in the capacitor when it is fully charged. (0) energy = = CV = J Page 11 of 9

12 9. What is the photoelectric effect? () Usual definition Outline a demonstration experiment for the photoelectric effect. (9) Source of light + colour filter + method of detecting loss of electrons ++ Name two uses of the photoelectric effect. () Bar code, furnace control,.. etc + Albert Einstein explained the photoelectric effect in the early part of the 0 th century. Give an outline of this explanation. (9) Incoming photon of suitable frequency All energy of photon absorbed by electron Some energy to overcome the work function Remaining energy as kinetic energy of emitted electron any three =+ It is sometimes stated that the photoelectric effect is the reverse process of making X-rays. Explain why this statement would be made. () Photoelectric effect photon in electron out X ray electron in photon out Ultraviolet light of wavelength 0 nm is incident on a metal of work function 4.eV. Calculate (i) (ii) the threshold frequency of the metal 19 φ threshold frequency = = = Hz 4 h. 10 the maximum kinetic energy of an emitted electron 1 hc mv = φ λ = = J 8 (iii) the maximum speed of an emitted electron. (0) v = v = ms (Planck s constant = 19 1 ev = J ) Js ; speed of light = ms ; Page 1 of 9

13 10. Answer either part (a) or part (b) (a) In nuclear reactions charge, momentum and mass-energy are conserved. Explain clearly the meaning of this statement. (1) Total charge before reaction = total charge after reaction Total momentum before reaction = total momentum after reaction Mass energy before reaction = mass energy after reaction An example of α decay is given by 9 U 90 Th + He + E Calculate (i) the energy released and state the nature of the energy mass before = mass after = = loss in mass = u energy = Δ mc = ( 10 ) = J The nature of the energy is kinetic energy of the two particles (ii) the energy of both particles after the reaction. (4) the energy is divided in the ratio of 4 : 4 4 Th gets 8 of J = J 4 He gets 8 of J =.7 10 J (mass of U = u; mass of Th = u; mass of He = u 1 u = kg ; speed of light = ms ) Name the four fundamental forces of nature and give two properties of each. (1) Gravitational, electromagnetic, strong nuclear, weak nuclear =++ Give the quark composition of the proton and the neutron. (8) Proton u u d 4 Neutron u d d 4 Page 1 of 9

14 (b) Draw and label a simple diagram of the moving coil galvanometer. (1) Magnet Spring Iron cylinder Scale Wire frame pointer any four +++ For the moving coil galvanometer (i) state the principle on which it is based current carrying conductor in a magnetic field experiences a force (ii) how would you show that the scale is linear torque due to current = restoring torque NBIld = kθ I θ (iii) how would you increase the sensitivity (18) larger N, B, l, d smaller k any two + 4 A galvanometer gives a full scale deflection for 5 10 A and has a resistance of 10Ω. (a) Calculate the value of the resistance needed to convert it to a voltmeter reading 5 V full scale V I { Rm Rg } = = 5 10 { 10} + R m = R + 10 m 9990Ω = Rm (b) calculate the value of the resistance needed to convert it to an ammeter reading 5 A full scale. (0) V = I R = = 5 10 V 4 g g g 4 Is It Ig A Vs 5 10 Rs 1 10 Is = = = 4 = = = Ω The scale of the analog ohmmeter decreases as you go from left to right. Explain why this is so. () Larger current. Needle moves to the right.. smaller resistance Page 14 of 9

15 11. (a) Name the three effects of an electric current (7) heating, chemical, magnetic ++ (b) What is the purpose of a fuse in an electrical circuit (7) To limit the size of current to prevent overheating 4+ (c) Why do only some domestic appliances have an earth connection (7) Only for appliances with metal on outer surface 7 (d) What is the colour code for the wires in a three pin plug (7) Live.brown Neutral.blue Earth.green, yellow (stripes) ++ (e) (f) (g) (h) R The voltage in Irish homes has a peak value of 5 V. What is the corresponding value of the root-mean-square voltage. (7) 5 = 0V 7 calculate the resistance of an electrical cable of length km, diameter mm which has a resistivity of Ω m (7) ρ l = = = 158Ω 7 π r π 1 10 ( ) If a 4 W bulb was inserted into a circuit where the voltage was 1 V, which of the following fuses would be most suitable; 1 A, A; 5 A. Explain your choice. (7) P 4 I = = = A normal operating current 4 V 1 Choose a A fuse During the 1970 s consideration was given to building a nuclear power station for generating electricity in Ireland. Give two advantages that nuclear power stations have to offer. (7) Great reduction in green house gas emissions Less dependency on fossil fuels 4+ Page 15 of 9

16 1. Answer any two of the following parts (a), (b), (c), (d) (a) State the two conditions needed for a body to be in equilibrium. () Usual two conditions = The uniform metre stick below has a weight of 7 N. Is it in equilibrium? Prove you answer by using the relevant mathematics. (18) Up force = 1+0= N Down force = = N up = down Take moments about zero on metre stick Clcocwise moments = = 17.4Nm Anticlockwise = = 17.4 Nm What is the purpose of a lever (4) The purpose of a lever is to amplify a force eg lift a large rock 4 (b) Define sound intensity () Usual definition Explain the difference between the threshold of hearing and the range of frequencies audible to the human ear. () Threshold of hearing is lowest sound intensity audible to human ear Range of frequencies are the frequencies humans can hear Sound is emitted equally in all directions from a point source of W. If no sound energy is absorbed or reflected calculate the sound intensity at a distance of.5 m from the source (1) Sound intensity = power = =.8 10 Wm 4πr 4 π.5 1 If the sound intensity is increased by a factor of 4 what is the increase in the sound intensity level. (4) Sound intensity add db Sound intensity 4 add db 4 (c) Name and state the two laws of electromagnetic induction (1) Faraday and Lenz usual statements + A copper pipe 1.5 m long is held vertically. A strong cylindrical shaped magnet is allowed to fall freely down the inside of the pipe. The time for the fall is greater than it would be if the pipe was made of plastic. Explain why this is so. (1) Falling magnet gives changing magnet flux Emf induced in copper ( a conductor) Current flows in copper ( aconductor) Current oposes falling magnet Name an electrical device that is based on the principle of electromagnetic induction (4) dymano, transformer 4 Page 1 of 9

17 (d) What is the meaning of half life for a radioactive substance () Usual definition 4 1 The decal constant for a radioactive substance is s. What percentage of the substance is still radioactive after 4 hours. (1) T ln ln = = = 1 4 λ seconds = 1 hour Start 100% After 1 hour.50% After hour 5% After hour 1.5% After 4 hour.5% Name a device for measuring levels of radioactivity. () Geiger counter Name two sources of background radiation on the earth (7) Radon gas, cosmic radiation, natural deposits of uranium 4+ Page 17 of 9

18 ORDINARY LEVEL SECTION A (10 marks) 1. A student performed an experiment to verify Boyle s law. The student measured and recorded values for the volume of a gas for a range of different values of pressure. The table below shows the data recorded by the student Draw and label a diagram of the apparatus that was used in this experiment. (1) Container of gas Method for measuring pressure Method for measuring volume Method to alter volume or pressure Fill in the bottom row of the above table which will give the values for 1 Volume. (5) Pressure / kpa Volume / cm / cm Volume mark 5 Plot a graph on graph paper with pressure on the y-axis and 1 Volume on the x-axis. (1) P/KPa / cm Volume Correct label on axes, points plotted, good line. + + How does the graph verify Boyle s law. () The graph is a straight line through the origin + Give one precaution that should be taken to improve the accuracy of the experiment. (5) Constant mass / fixed temperature / avoid error of parallax when measuring pressure or volume 5 Page 18 of 9

19 . An experiment was carried out by a student to measure the speed of sound in air. A hollow glass tube was inserted into a large graduated cylinder of water. Different tuning forks were sounded one by one and they were held over the open end of the glass tube. This open end of the tube protruded above the water level. The tube was raised out of the water until resonance was detected. Draw and label a diagram of the experimental arrangement. (1) Graduated cylinder of water Hollow glass tube Tuning fork Tube protruding out of water How did the student detect the resonance. () Sound got louder How did the student measure the wavelength of the sound when resonance occurred. () λ = 4 l+ d { } How did the student find the value of the frequency when resonance occurred. () During resonance frequency of vibrating air = frequency of tuning fork When the frequency value was 5 Hz the student recorded a wavelength value of 1. m. Using this pair of values calculate the value of the speed of sound in air. () c = f λ = 5 1. = 40.48ms 1 Give one precaution that the student might take to improve the accuracy of the experiment. (4) Avoid error of parallax when measuring length with metre stick/ avoid very high frequencies. (c = f λ ) 4 Page 19 of 9

20 . A student performed an experiment with the purpose of verifying Snell s law and at the same time to measure the refractive index of a glass block. The student arranged for a beam of light to fall on and pass through a glass block. The following data was recorded. Draw and label a diagram of the experimental arrangement (1) Glass block Incident ray Refracted ray Anlges I and r labelled Fill in the above table completely and find an average value for the refractive index of the glass. Angle of incidence i Angle of refraction r sin i sin r sin i sin r Average value = Any five 5 Correct method for average (1) Using the above data plot a graph with sin i on the y-axis and with sin r on the x-axis. (1) sin i sin r Labels, points 1, good line Explain how the graph verifies Snell s law. (4) Straight line through origin verifier sin i sin r 4 Page 0 of 9

21 4. An experiment was undertaken by a student to investigate the variation of current with potential difference for a copper sulphate solution. The student used a V battery, an ammeter, a voltmeter, a rheostat (variable resistor), copper electrodes, several connecting wires and a beaker of copper sulphate solution. The value of potential difference (voltage) was measured along with the corresponding value of current. The rheostat was adjusted and the voltage and current were again recorded. The data is shown in the table below. Potential difference / V Current / V Draw and label a diagram of the experimental arrangement. (1) electrodes Power supply Ammeter and voltmeter correctly positioned Method for adjusting current/ voltage Plot a graph with potential difference on the y-axis and current on the x-axis. (1) 5 4 P. D / V I / A.0 Label axes, points, good line What conclusion can you draw from the graph about the relationship between the current and the potential difference for the copper sulphate solution. (4) I V 4 What would you observe in the experiment if the ammeter was placed where the voltmeter should be and the voltmeter was placed where the ammeter should be. () Current would not flow Using just one pair of values from the above table of data calculate a value for the resistance of the copper sulphate solution. () Any calculation V R = = I = Ω Page 1 of 9

22 5. Answer any eight of the following parts (a), (b), (c) etc. (a) Calculate the work done when a force of 5 N moves an object m in the same direction as the force. (7) 10 joule 7 (b) (c) (d) A particle starting from rest is given an acceleration of 5ms for seconds. Calculate the value of the final speed. (7) 1 (v = u + at) v = = 0ms 7 A fish swimming in a tank of water appears nearer to the surface than it really is when viewed from above the water. What is the cause of this? (7) Refraction of light as it passes from water to air 7 Draw a diagram to show what happens to a beam of white light when it is passed through a prism (7) Show light undergoing dispersion, separation of colours 7 (e) What is the purpose of a diode in an electrical circuit? (7) To allow current flow in only one direction. 7 (f) A plastic rod was rubbed with a cloth and the rod gained electrons from the cloth. What type of charge does the rod now have? (7) Negative 7 (g) Name any two of the three methods of heat transfer. (7) Conduction, convection, radiation 4 + (h) A heat pump transfers heat energy from a cold region to a warmer region. Give an example of a heat pump you would find in the kitchen of most homes. (7) Refrigerator 7 (i) Name the scientist who discovered X-rays. (7) W. Rontgen 7 (j) At the moment electricity is generated in nuclear power stations using nuclear fission. Name the radioactive material that is used as a fuel in the nuclear reactor. (7) Uranium 7 Page of 9

23 . Weight is a vector quantity and mass is a scalar quantity. Give one other difference between weight and mass. () Weight in N mass in kg / weight has direction mass no direction State clearly the difference between a vector quantity and a scalar quantity. () Vector has magnitude and direction Scalar has magnitude only State Newton s law of universal gravitation. () F = Gmm 1 d explain notation Calculate the value of the acceleration due to gravity on the surface of the earth given 4 that the radius of the earth is.4 10 m, the mass of the earth is 10 kg and the 11 universal constant is.7 10 Nm kg. (1) 11 4 GM g = = = 9.8ms R (.4 10 ) 1 What happens to the value of the acceleration due to gravity as you move away from the surface of the earth? () Acceleration due to gravity gets smaller as you move away from centre of earth What would you need to do to experience the sensation of zero gravity? (5) Extremely far from any planet / state of free fall 5 A team of scientists were examining the values of the acceleration due to gravity on different planets. The values were compared to the values here on earth. What would be the difference between the acceleration due to gravity (i) if a planet had the same radius as the earth but had twice the mass of the earth. Acceleration would be doubled (ii) if a planet had the same mass as the earth but had twice the radius of the earth (15) Acceleration would be four times smaller 9 GM ( g = ) R Page of 9

24 7. What is the difference between a longitudinal wave and a transverse wave. Give an example of each. (1) For a transverse wave the direction of movement of the energy is perpendicular to the direction of movement of the medium Example light wave etc. For a longitudinal wave..is parallel. Example sound wave Outline a laboratory demonstration experiment to (i) show that sound needs a medium in which to travel usual demo.bell jar, electric bell, vacuum pump hear sound with air in jar no sound audible with vacuum (ii) show that sound is a wave. (18) usual demo.. two speakers constructive and destructive interference hence sound a wave Note ; no need to comment on difficulties of doing this demo indoors!! An ambulance is approaching a person and the siren is emitting a sound of a particular frequency. As the ambulance passes by the person and moves away from the person the sound appears different. (a) What difference in the frequency of the sound will be noticed (7) Frequency lower as siren moves away 7 (b) What would be the difference in the wavelength of the sound (7) Wavelength longer as siren moves away 7 (c) What is the name of this effect () Doppler effect (d) Give one everyday use of this effect. () Measuring speed of a car etc. Page 4 of 9

25 8. (a) State the laws of reflection () Usual statement + Draw a ray diagram the show the formation of an image in a convex mirror (9) Label object and image rays correctly drawn Overall Give one everyday use for a convex mirror. () Rear mirror in car / security mirror An object is placed a distance of 1 cm from a concave mirror of focal length 8 cm. Calculate the position of the image = 1 v = = = v v = 4 cm 7 If the object is cm in size what is the size of the image (10) Magnification = v u 4 = = 1 Image size = = 4 cm (b) Draw a ray diagram to show the formation of an image in a diverging lens. (9) Label object and image rays correctly drawn Overall What is the type of lens found in the human eye? () Converging (convex) The lens is flexible and can have different values of focal length. Why is this? (7) To allow the eye focus light from different distances + 4 What type of lens is used to correct short-sightedness? () Diverging (concave) ( image size v + = magnification = = ) u v f object size u Page 5 of 9

26 9. What is an electric current? () Flow of charge Name the three effects of an electric current and give an everyday example of the use of each of the three effects (18) Heating electric kettle + Magnetic. Electric motor + Chemical electrolysis + The voltage in Irish homes is 0 V. A person buys a microwave oven that is rated 900 Watt. Calculate the current that is normally used by the oven. () P= V I 900 = 0 I I =.91Amp If the plug of the microwave oven had a A fuse what would you notice when the oven is switched on at full power for the first time. Give a reason for your answer(9) The oven would not work The fuse would blow.91 is bigger then Energy is measured in the joule. Power companies tend to use the kilowatt-hour as their unit of energy. Why is this? () The Joule is a very small amount of energy How many joules of energy is there in 1 kilowatt-hour. () = If the cost of 1 kilowatt-hour is 15 cent, calculate the cost of using a 500 W bulb for a full day. (8) Number of units = = 1 4 Cost = 15cent 1 = ( P = V I ) 10. What is the difference between photoelectric emission and thermionic emission? (1) Photoelectric removal of electrons using light Thermionic..removal of electrons using heat Give two properties of electrons () Small mass / negative charge / orbit the nucleus / dual nature / any two + Electrons were originally known as cathode rays. Name the Irish scientist who changed the name to the electron () G J Stoney In the cathode ray tube shown above (i) Why do the electrons travel towards the anodes? () Anodes are positive and high voltage + (ii) Why are the electrons deflected () Due to electric field (iii) How could you deflect the electron beam downwards () Reverse direction of electric field (iv) Why does a spot of light appear on the screen? (7) Electrons cause fluorescence 7 (v) Name two instruments in everyday life that are based on the cathode ray tube (7) Television / oscilloscope / ECG / EEG 4 + Page of 9

27 11. Read the following passage and answer the accompanying questions Electrical transformers are used to transform voltage from one level to another, usually from a higher voltage to a lower voltage. They do this by applying the principle of electromagnetic induction between coils to convert voltage and/or current levels. Electric motors use electrical energy to produce mechanical energy typically through the interaction of magnetic fields and current carrying conductors (a) What is electromagnetic induction? (7) Changing magnetic flux induces an emf 7 (b) What material is the transformer core made of? (7) Iron 7 (c) Transformers work with a.c but not with d.c Explain why this is so. (7) d. c. cannot give a changing magnetic flux 7 (d) Give an example of where you would use a transformer in everyday life. (7) Phone charger / lap top / 7 (e) (f) (g) (h) Explain the difference between a step-up transformer and a step-down transformer (7) Step up..greater secondary voltage 4 Step down smaller secondary voltage The input voltage is 0 V and the primary coil has turns. If the secondary coil has 00 turns calculate the value of the output voltage (7) 0 = 4V 7 5 What happens when a current carrying conductor is placed in a magnetic field? (7) Experiences a force 7 Calculate the force on a conductor of length 50 cm carrying a current of A when placed in a magnetic field of magnetic flux density T (7) F = BIl = 0.5 = N 7 V N i p = V N o s Page 7 of 9

28 1. Answer any two of the following parts (a), (b), (c), (d). (a) Define the moment of a force () Usual definition The uniform metre stick below (centre of gravity at the 50 cm mark) has a weight of 1 N. (i) Calculate the total upward force on the metre stick () 1 N (ii) Calculate the total downward force on the metre stick () 1 N (iii) (iv) Calculate the moment of the upward forces about an axis through the 0 cm mark on the metre stick () =.54Nm Calculate the moment of the downward forces about an axis through the 0 cm mark on the metre stick () =.5 Nm (v) Is the metre stick in equilibrium? (4) Yes within acceptable experimental limits 4 If student says no as.5 us not exactly.54 also award the marks! (b) What is the difference between heat and temperature. () Heat a form of energy and temp a measure of hotness + What are the units used for heat and what are the units used for temperature () Heat joule temp..degree Celsius / Kelvin + A thermometric property is a physical property that changes measurably with temperature. Give two examples of a thermometric property. () Any two + What is the difference between latent heat of fusion and latent heat of vaporisation? () Fusion..melting vaporisation liquid to gas + Humans perspire when their body temperature rises. What is the purpose of this? (4) To lower body temp 4 (c) Define capacitance. () Usual Name two everyday uses of capacitors. () Tuning a radio / smooth output from rectifier + Calculate the capacitance of a parallel plate capacitor if the common area of the plates is 0.1m and the plates are a distance of mm apart Let the permittivity of the medium between the plates be 5 10 Fm. (1) ε A 10 C = = =.5 10 F d 10 Page 8 of 9 1

29 If the voltage across the above capacitor is V calculate the charge stored on the capacitor (4) 10 9 Q CV C ( = = = 4 ε A Q C = C = ) d V (d) Give two properties each for α, β and γ radiation (1) α...positive / poor penetration / good ionising + β..negative / fair penetration / fair ionising + γ.neutral / god penetration / poor ionising + Name an instrument that can be used to measure levels of radioactivity. () Geiger Muller The half-life of a radioactive material is given as 4 hours. What is meant by this? () After 4 hours only half of the sample will be radioactive Give two everyday used for radioactive materials. (7) Smoke detectors / medical / carbon dating. 4 + Page 9 of 9

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