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PHYSICS – ORDINARY LEVEL

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TIME: 3 HOURS_______________

Answer three questions from Section A and fi ve questions from Section B.

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N.B. Relevant data are listed in the Formulae and Tables booklet, which is available from the Superintendent.

*B16*

Pre-Leaving Certifi cate Examination, 2015Triailscrúdú na hArdteistiméireachta, 2015

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SECTION A (120 marks)

Answer three questions from this section.Each question carries 40 marks.

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1. You carried out an experiment to investigate the relationship between the acceleration of a body and the force applied to it. You did this by applying a force to a body and measuring the resulting acceleration. The table shows the data recorded during the experiment.

Force (N) 0.1 0.2 0.25 0.3 0.35 0.4 0.5 0.6

Acceleration (m s–2) 0.2 0.4 0.5 0.6 0.7 0.8 1.0 1.2

(i) Draw a labelled diagram of the apparatus you used. (9)

(ii) How did you measure the applied force? (6)

(iii) How did you minimise the effect of friction during the experiment? (6)

(iv) Plot a graph on graph paper of the body’s acceleration (X-axis) against the force (Y-axis) applied to it. (6)

(v) Using the graph, determine the mass of the body used in this experiment. (6)

(vi) What does your graph tell you about the relationship between the acceleration of the body and the force applied to it? (7)

2. You carried out an experiment to measure the wavelength of a monochromatic light source using a diffraction grating. The diffraction grating had 400 lines per mm.

(i) Draw a labelled diagram of the apparatus you used. (12)

(ii) Name a source of monochromatic light. (4)

(iii) State what measurements you took during the experiment. (6)

(iv) What is the distance between each line on the diffraction grating? (6)

(v) How did you determine the wavelength of the light? (6)

(vi) Give one precaution that you took to get an accurate result. (6)

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3. 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)

(ii) Describe how you found the position of the image formed by the lens. (6)

(iii) What measurements did you take? (9)

The table shows the measurements recorded by you during the experiment.

U (cm) 20 30 40 50 60

V (cm) 64 43 41 35 20

(iv) Using the formula VUf111

or otherwise and the above data, fi nd an average value

for the focal length f of the lens. (13)

4. In an experiment to verify Joule’s law, a heating coil was placed in a fi xed mass of water. A current I was allowed to fl ow through the coil for a fi xed length of time and the rise in temperature Δθ was recorded. This was repeated for different values of I.

The table shows the data recorded.

(i) Draw a labelled diagram of the apparatus used. (12)

(ii) How was the current changed during the experiment? (4)

(iii) Copy the table and complete it in your answer book. (6)

I (A) 1.0 1.5 2.0 2.5 3.0 3.5 4.0

I2 (A2) 9

Δθ (°C) 2.3 5.0 8.5 13.5 21.0 26.0 35.2

(iv) Using the data in the completed table, draw a graph on graph paper of Δθ against I 2. Put I 2 on the X-axis. (12)

(v) Explain how your graph verifi es Joule’s law (Δθ α I 2). (6)

James Joule

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SECTION B (280 marks)

Answer fi ve questions from this section.Each question carries 56 marks.

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5. Answer any eight of the following parts (a), (b), (c), etc.

(a) A horse gallops at a constant speed of 10 m s–1. Calculate the distance travelled by the horse in 2 minutes.

(b) State Newton’s second law of motion.

(c) State Boyle’s law.

(d) What is the purpose of a fuse in this plug?

(e) Name one device that uses a transformer.

(f) Name the electrical component represented in the diagram.

(g) What is meant by the half-life of a radioactive substance?

(h) The half-life of a radioactive element is 3 days. What fraction of a sample of the radioactive element will remain after 9 days?

(i) Name the type of nuclear reaction that occurs in the Sun.

(j) In semiconductors, what is meant by doping?

(8 × 7)

Live wire

Fuse

Cable grip

Outer insulation

Neutral wire

Earth wire

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6. Defi ne (i) velocity, (ii) acceleration. (12)

Describe an experiment to measure the acceleration due to gravity, g. (18)

A stone is thrown straight up from the ground with an initial speed of 25 m s–1. Calculate the height reached after 2 s. Use the equation (s = ut + ½ a t2). (5)

Describe how the speed of the stone changes as it rises to its highest point. (6)

Calculate the time it takes the stone to reach its highest point. Use the equation (v = u + at). (9)

How long will it take the stone to return to the ground? (3)

At what height will the stone’s kinetic energy be equal to its potential energy? (3) (acceleration due to gravity, g = 9.8 m s–2)

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7. “When a wave meets an object, diffraction occurs. A wave with the correct frequency can also cause resonance in an object.”

Explain the underlined terms. (18)

How would you demonstrate diffraction in the laboratory? (8)

The pitch of a note emitted by a siren of a fast moving police car appears to change as it passes a stationary observer.

(i) Name this phenomenon. (6)

(ii) Explain how this phenomenon occurs. (6)

(iii) Give an application of this phenomenon. (6)

If you are standing a few hundred metres from a fi reworks display, you will often see the fl ash of light from an exploding fi rework before you hear the sound of the explosion.

What does this tell you about the speed of sound in air? (6)

Name a medium in which sound travels faster than it does in air. (6)

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8. (i) What is heat? (6)

(ii) Explain how heat is transferred in a solid. (9)

(iii) Describe an experiment to compare the rates of heat transfer through different solids. (12) (iv) Explain the term U-value. (6)

The temperature of an object is measured by using a thermometer, which is based on the variation of its thermometric property.

(v) Give an example of a thermometric property. (6)

An electric kettle contains 1.5 kg of water. The specifi c heat capacity of water is 4180 J kg–1 K–1.

(vi) Calculate the amount of energy required to raise the temperature of the water from 15ºC to 100ºC. (9)

(vii) The kettle takes 4 minutes to heat the water from 15ºC to 100ºC. Calculate the power of the kettle. (Assume all the energy supplied is used to heat the water.) (8)

(Q = mc∆θ; P = W/t)

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9. “The capacitance of a parallel plate capacitor depends on the distance between the plates”

(i) What is a capacitor? (6)

(ii) Describe an experiment to investigate the above statement. (18)

(iii) Name another factor that affects the capacitance of a parallel plate capacitor. (6)

(iv) Mention two common uses of capacitors. (8)

A voltage supply of 20 V is connected across the capacitor in the fi gure above.

(v) What is the charge on the plates of the capacitor? Use the formula (Q = CV). (9)

(vi) What is the energy stored in the capacitor? Use the formula (E = ½ CV2). (9)

10. Alpha, beta and gamma (α, β, γ) are three types of radiation.

(i) Which type is short-wavelength electromagnetic radiation? (3)

(ii) Which type is a particle consisting of two protons and two neutrons? (3)

(iii) Which type is a fast moving electron? (3)

(iv) How would you detect radiation? (6) Nuclear fi ssion occurs in a nuclear reactor.

(v) What is nuclear fi ssion? (6)

(vi) What is the role of neutrons in nuclear fi ssion? (6)

(vii) Name a fuel used in a nuclear reactor. (6)

(viii) In a nuclear reactor, how can the fi ssion be controlled or stopped? (6)

(ix) How is the energy produced in a nuclear reactor used to generate electricity? (9)

(x) Give one advantage and one disadvantage of a nuclear reactor as a source of energy. (8)

DANGER

RADIOACTIVEMATERIAL

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11. Read this passage and answer the questions below.

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. Google took a step in that direction recently with the acquisition of Titan Aerospace, a maker of solar-powered drones that can help boost Internet access to remote areas. Titan’s drones are able to run for fi ve years at an altitude of 20,000 meters. They can perform similar functions to geostationary satellites, but are less costly.Google has already begun work on Project Loon, which uses large balloons for transmitting Internet signals to regions that are not now connected. Tests were carried out last year in New Zealand, and one balloon circumnavigated the world in 25 days. Google’s plan is to keep the balloons aloft in the stratosphere for 100 days. In remote areas, Internet speeds are approximately 3 Mbps whereas in Ireland speeds up to 150 Mbps are possible.www.phys.org

(a) The solar-powered drones absorb solar energy and turn it into electricity. The solar energy available at 20,000 m is 4 times more than that available on the earth’s surface. What causes this difference?

(b) What is a geostationary satellite?

(c) Give an application of a geostationary satellite.

(d) The letter K represents a factor of one thousand, eg 1 Km = 1000m. What does the letter M represent?

(e) What is Mbps short for?

(f) If the average Internet speed in Ireland is 50 Mbps, how long will it take to download a 4Mb picture?

(g) If a balloon is at an altitude of 20,000 m and travels around the world in 25 days, how fast is it travelling?

(h) If the balloon stayed aloft for 100 days, how many times would it travel around the world?

(radius of earth = 6,371 km)(8 × 7)

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12. Answer any two of the following parts (a), (b), (c), (d).

(a) The diagram shows a U-shaped magnet. Copy the diagram and show on it, the magnetic fi eld lines due to the magnet. (6)

Describe an experiment to demonstrate that a current-carrying conductor in a magnetic fi eld experiences a force. (12)

List two factors that affect the size of the force on the conductor. (6)

Name one device that is based on the principle that a current-carrying conductor in a magnetic fi eld experiences a force. (4)

(b) State the laws of refl ection of light. (12)

When you look at a plane mirror you see a virtual image. Explain the underlined terms. (6)

Give one other property of the image in a plane mirror. (4)

The diagram shows stage lighting similar to that found in most theatres. Only red, green and blue lights are needed to create most lighting effects. Explain why. (6)

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(c) Describe, with the aid of a diagram, an experiment to show that a force exists between electric charges. (12)

What is meant by point discharge? (6)

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)

(d) A p-n junction (diode) is formed by doping adjacent layers of a semiconductor. A depletion layer is formed at their junction.

(i) Explain the underlined terms. (9)

(ii) How is a depletion layer formed? (6) The diagram shows two diodes connected to two bulbs A and B, a 6 V supply and a switch.

(iii) What is observed when the switch is closed? (6)

(iv) Explain why this happens. (7)

A

B

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