Answer three questions from Section A and five questions from Section B.

Transcription

1 L.35 PRE-LEAVING CERTIFICATE EXAMINATION, 2017 PHYSICS ORDINARY LEVEL TIME 3 HOURS Answer three questions from Section A and five questions from Section B. Relevant data are listed in the Formulae and Tables booklet, which is available from the Superintendent L.35 1/12 page 1 of 12

2 Answer three questions from this section. Each question carries 40 marks. SECTION A (120 marks) 1. In an experiment to verify Boyle s law for a fixed mass of gas, the volume of a gas, V, was measured for a number of different pressures, P. The table below shows the data recorded. P (kpa) V (cm 3 ) V (cm 3 ) (i) (ii) Draw a labelled diagram of the arrangement of the apparatus used in this experiment. (12) State one other quantity, other than the fixed mass of gas, that was kept constant in this experiment. (4) (iii) Copy the table above and complete it in your answerbook. (6) (iv) Using the data in the completed table, draw a graph on graph paper of P against 1 V. (12) (v) Explain how your graph verifies Boyle s law. (6) 2. During an experiment to measure the specific heat capacity of a substance (e.g. water or a metal), a student recorded a number of temperature and mass readings. The student used these measurements to calculate the specific heat capacity of the substance. (i) Draw a labelled diagram of the arrangement of the apparatus used in this experiment. (12) (ii) What temperature measurements did the student take during the experiment? (6) (iii) What mass measurements did the student take during the experiment? (6) (iv) Write the formula that would have been used by the student to calculate the specific heat capacity of the substance. (10) (v) Give an assumption that was made by the student when using this formula that could result in an error in the final value recorded. (6) L.35 2/12 page 2 of 12

3 3. An experiment was carried out to investigate the relationship between the fundamental frequency, f, of a stretched string and the length of the string, l. The length of a stretched string was measured when its fundamental frequency of vibration corresponded to the frequency of a vibrating source of sound. This was repeated for a number of different frequencies. (i) Draw a labelled diagram of the arrangement of the apparatus that may have been used to collect this data. (12) (ii) State one quantity that is kept constant during this experiment. (6) (iii) How were the frequencies of the vibrating sources of sound changed during the experiment? How were the corresponding lengths of the stretched strings determined? (9) (iv) What is the relationship between frequency and length that would have been discovered in this experiment? (6) (v) Draw a sketch of the graph that would verify this relationship. (7) 4. A student carried out a laboratory experiment to investigate how the resistance, R, of a thermistor varies with temperature, θ. The table below shows the data collected. θ ( C) R (Ω) (i) Draw a labelled diagram of the arrangement of apparatus used in this experiment. (12) (ii) Name the instruments used to measure the resistance and temperature values. (6) (iii) Plot a graph, on graph paper, of the resistance against temperature, θ, for a thermistor. (12) (iv) Use your graph to determine at what temperature the resistance of the thermistor is 1600 Ω. (6) (v) How does the resistance of the thermistor vary with temperature? (4) L.35 3/12 page 3 of 12

4 Answer five questions from this section. Each question carries 56 marks. SECTION B (280 marks) 5. Answer any eight of the following parts, (a), (b), (c), etc. (a) Give an example of (i) a vector quantity and (ii) a scalar quantity. (b) Why is the acceleration due to gravity on the moon less than the acceleration due to gravity on the Earth? (c) What is the power developed by a person who lifts a weight of 60 N through a height of 5 m in 12 seconds? (d) What is meant by a thermometric property? (e) Why is the decibel adapted, db(a), scale used when constructing sound-level meters? (f) What is the power of a convex lens of focal length 10 cm? (g) State two uses for capacitors. (h) How does a residual current device (RCD) act as a safety device in a circuit? (i) What is a photon? (j) Choose from the list below the scientist who (i) named the electron, and (ii) measured the charge on the electron. Bohr Stoney Millikan Chadwick (8 7) L.35 4/12 page 4 of 12

5 6. Define momentum. (6) State the principle of conservation of momentum. (9) Explain how the principle of conservation of momentum applies in launching a rocket ship. (8) A white snooker ball of mass 0.18 kg travelling at 0.5 m s 1 strikes a stationary black snooker ball of mass 0.2 kg. After the collision the white snooker ball travels at 0.1 m s 1 in the same direction. The black ball travels in the same direction as the white ball after the collision. Calculate (i) (ii) the momentum of the white ball before the collision the loss of momentum of the white ball during the collision (iii) the speed of the black ball after the collision. (21) After the collision the white ball travels a distance of 2 m before it stops, without striking any cushion. Calculate (iv) the deceleration of the white ball after the collision (v) the time after the collision it takes the white ball to stop. (12) L.35 5/12 page 5 of 12

6 7. In a periscope light is deflected twice through 90. Light can be deflected by reflection using mirrors or by total internal reflection using prisms. Mirror (i) Explain the underlined terms. (12) (ii) State the laws of reflection of light. (9) Light ray (iii) What is the angle of incidence in the periscope shown for both mirrors? (4) (iv) Give two properties of the image produced 45 angle upon reflection from a plane mirror. (6) Mirror Eye Periscope (v) Give an application for (a) a concave mirror and (b) a convex mirror. (6) (vi) Draw a ray diagram showing a periscope using two prisms instead of two mirrors. (12) (vii) If the critical angle for the glass in the prism is 41, calculate the refractive index of the glass. (7) 8. Light waves are electromagnetic waves and sound waves are mechanical waves. Distinguish between electromagnetic waves and mechanical waves. (6) State two other differences between light waves and sound waves. (9) Draw a waveform of a musical note and mark in the (i) wavelength and (ii) amplitude of the wave. (9) If the (i) pitch and (ii) loudness of the musical note increase, how does the shape of the waveform change? (8) A note of frequency 480 Hz is produced by a man playing a flute on the side of a street. What is the wavelength of the note? (9) A woman travelling in a car hears the flute while passing the man playing the flute. What difference does the woman observe between when (i) she is travelling towards the man and (ii) she is travelling away from him? What name is given to this change? (10) Give an example of where this effect is observed with light waves. (5) (speed of sound in air = 340 m s 1 ) L.35 6/12 page 6 of 12

7 9. Coulomb s law of force between electric charges is an example of an inverse square law. State Coulomb s law of force between electric charges and give an example of another inverse square law. (12) Draw a labelled diagram of a gold leaf electroscope and explain how a positive charge could be placed on the electroscope by induction. (18) What would be observed if a negatively-charged object was brought near the electroscope? Explain this observation. (9) What is meant by point discharge? Copy the diagram below into your answer book and show how a negative charge is distributed on the metal conductor. (12) Explain how this conductor could be used as a lightning conductor to protect a building. (5) 10. What is radioactivity? (6) Name the scientist who discovered radioactivity and after whom the unit of radioactive decay is named. (3) (i) (ii) What is the nature of the three forms of radiation: alpha (α)-particles, beta (β)-particles and gamma (γ)-rays? (10) Describe an experiment that compares the penetrating power of α-, β- and γ-radiation. (12) Carbon-14 ( 14 6C ) is a radioactive isotope of carbon with a half-life of 5730 years. It decays by emitting a β-particle. (iii) How many protons and neutrons does a Carbon-14 atom contain? (6) (iv) How long does it take for a sample with 800 billion Carbon-14 nuclei to decay until 100 billion Carbon-14 nuclei remain? (6) (v) Using page 79 of the Formulae and Tables booklet, determine what element is formed after a β-particle is emitted from Carbon-14 ( 14 6C ). (6) (vi) Give two uses for radioactive substances. (7) L.35 7/12 page 7 of 12

8 11. Read this passage and answer the questions below. The transistor was invented at Bell Labs in New Jersey in 1947 by John Bardeen, Walter Brattain and William Shockley. The transistor is at the heart of almost all electronics and so it is one of the most important inventions of the 20 th century. Shockley opened the Shockley Semiconductor Laboratory of Beckman Instruments in Palo Alto, California. He searched universities for the brightest young graduates to build the new company. This was truly the genesis of Silicon Valley and some of its culture that still exists today. Shockley is credited with bringing the silicon to Silicon Valley. Shockley s management style was abrasive and eight people, known as the traitorous eight, resigned and with seed money from Fairchild Camera and Instrument, they created Fairchild Semiconductor Company. Almost all semiconductor companies, especially Intel, AMD and National Semiconductor (now part of Texas Instruments), have their roots in Fairchild in one way or another. It was where silicon-based integrated circuits began, which as it turns out, is the prevailing technology still in use today. The second big step, the invention of the integrated circuit, took place simultaneously at Fairchild and Texas Instruments from 1957 to Jean Hoerni at Fairchild developed the planar transistor; then Jack Kilby at Texas Instruments and Robert Noyce at Fairchild developed the integrated circuit. This turned out to be the big breakthrough. Until that point transistors were built one at a time and wired together manually. By 1962 Fairchild was producing integrated circuits with about a dozen transistors. Much has changed in the intervening years but this same basic principle is how we build today s chips with billions of transistors. So those two inventions, the transistor and the integrated circuit, really are the key to electronics today and the ways in which semiconductors affect our lives. (Adapted from (a) (b) (c) (d) (e) (f) (g) (h) What are integrated circuits? Why was the invention of the integrated circuit important in the development of electronics? A transistor consists of different types of semiconductor material. What is a semiconductor? Within a transistor are layers of p-type and n-type semiconductors. Give one difference between p-type and n-type semiconductors. Explain how p-type and n-type semiconductors are used in a semiconductor diode. Draw a circuit diagram showing a semiconductor diode in forward bias. A semiconductor diode is used in rectification of a.c. electricity. What is rectification? Name a material, other than silicon, used in the manufacture of semiconductors. (8 7) L.35 8/12 page 8 of 12

9 12. Answer any two of the following parts, (a), (b), (c), (d). (a) State one of the conditions that is necessary for a body to be in equilibrium. (6) A uniform plank, of length 2 m and mass 5 kg, is placed on two supports as shown in the diagram. The plank is in equilibrium. F 20 cm 50 cm (i) Calculate the weight of the plank. (6) (ii) Find the clockwise moment of the weight about the 20 cm mark on the plank. (8) (iii) The clockwise moment of the weight about the 20 cm mark equals the anti-clockwise moment of the force F about the 20 cm mark. Calculate the value of the force F. (8) (acceleration due to gravity = 9.8 m s 2 ) (b) Dispersion of light can be observed in a rainbow. What is meant by dispersion of light? (6) Explain, using a diagram, how you would demonstrate the dispersion of light using a prism. In your diagram, indicate which ray is the red light and which is the violet light. (10) Name a piece of laboratory equipment that can disperse light by a method other than refraction. Which colour is dispersed the most using this piece of laboratory equipment? (6) Name the type of electromagnetic radiation that has a wavelength (i) just below visible light and (ii) just above visible light in the electromagnetic spectrum. (6) L.35 9/12 page 9 of 12

10 (c) Explain the term electromagnetic induction. (6) A transformer is based on electromagnetic induction. P R I M A R Y Input Coil Output Coil S E C O N D A R Y What is the difference between a step-up transformer and a step-down transformer? (8) There are 200 turns in the primary coil of a transformer and 45 turns in the secondary coil. Calculate the output voltage when 230 V a.c. is connected across the primary coil. (8) If all the energy is transferred in the transformer, and there is a resistance of 10 Ω in the secondary coil, what is the current flowing in the secondary coil? (6) (d) What is nuclear fission? (6) How is energy produced in a nuclear fission reaction? (9) Give one example of an element that could be used as fuel in a nuclear fission reactor. (6) What is the function of (i) control rods and (ii) the moderator in a nuclear fission reactor? (7) L.35 10/12 page 10 of 12

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