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# AQA A LEVEL PHYSICS EXAM PAPER 2 2020

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A-level
PHYSICS
Paper 2

Monday 1 June 2020 Afternoon Time allowed: 2 hours
Materials
For this paper you must have:
• a pencil and a ruler
• a scientific calculator
• a Data and Formulae Booklet.

Instructions
• Use black ink or black ball-point pen.
• You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages.
• If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s).
• Do all rough work in this book. Cross through any work you do not want to be marked.

Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 85.
• You are expected to use a scientific calculator where appropriate.
• A Data and Formulae Booklet is provided as a loose insert.

*JUN20740 201* IB/M/Jun20/E12 7408/2

Section A

Answer all questions in this section.

Do not write outside the box

A perfectly insulated flask contains a sample of metal M at a temperature of –10 °C.

Figure 1 shows how the temperature of the sample changes when energy is transferred to it at a constant rate of 35 W.

Figure 1

. State the melting temperature of M.

[1 mark]

temperature = °C

. Explain how the energy transferred to the sample changes the arrangement of the atoms during the time interval tA to tB.

Do not write
outside the box

[1 mark]

. State what happens to the potential energy of the atoms and to the kinetic energy of the atoms during the time interval tA to tB.
[2 marks]

. Describe how the motion of the atoms changes during the time interval tB to tC.
[1 mark]

Question 1 continues on the next page

Turn over ►

. The sample has a mass of 0.25 kg.

Determine the specific heat capacity of M when in the liquid state. State an appropriate SI unit for your answer.

[3 marks]

Do not write
outside the box

specific heat capacity = unit =

. Table 1 shows the specific latent heats of fusion l for elements that are liquid at similar temperatures to M.

Table 1

Element Caesium Gallium Mercury Rubidium
l / kJ kg−1 16 80 11 26

M is known to be one of the elements in Table 1.

Identify M.

[2 marks]

M =

Turn over for the next question

Do not write
outside the box

Figure 2 shows a moon of mass m in a circular orbit of radius r around a planet of mass M, where m << M.

box

Figure 2

The moon has an orbital period T. T is related to r by

T 2 = kr3

where k is a constant for this planet.
42

. 1

*06*

Show that k =

GM

[3 marks]

Table 2 gives data for two of the moons of the planet Uranus.

Table 2

box

Name T / days r / m
Miranda 1.41 1.29 × 108
Umbriel 4.14 X

. Calculate the orbital radius X of Umbriel.
[2 marks]

. Calculate the mass of Uranus.

[3 marks]

mass = kg

Question 2 continues on the next page

*07*

Turn over

Do not write outside the

Table 3 gives data for three more moons of Uranus.

Table 3

Name Mass / kg Diameter / m
Ariel 1.27 × 1021 1.16 × 106
Oberon 3.03 × 1021 1.52 × 106
Titania 3.49 × 1021 1.58 × 106

. Deduce which moon in Table 3 has the greatest escape velocity for an object on its surface.
Assume the effect of Uranus is negligible.

Do not write
outside the box

[3 marks]

Do not write outside the

. A spring mechanism can project an object vertically to a maximum height of 1.0 m
from the surface of the Earth.

Determine whether the same mechanism could project the same object vertically to a maximum height greater than 100 m when placed on the surface of Ariel.

Do not write
outside the box

[3 marks]

Turn over for the next question

Mass spectrometers are used to measure the masses of ions.

Figure 3 shows one part of a mass spectrometer.

box

Figure 3

A narrow beam consists of positive lithium ions travelling at different speeds. The beam enters a region where there is an electric field and a magnetic field.
The directions of the uniform electric field of strength E and the uniform magnetic field of flux density B are shown on Figure 3.

Most ions are deflected from their original path.
Lithium ions that travel at one particular speed are not deflected, and pass through the small aperture.

. 1 The positive lithium ion A in Figure 3 moves at a speed v.

Draw two labelled arrows on Figure 3 to show the directions of the electric force FE
and the magnetic force FM acting on A.
[1 mark]

. Lithium ions travelling at 1.5 × 105 m s−1 pass through the small aperture.

Calculate E.

B = 0.12 T

[2 marks]

box

E = V m−1

Question 3 continues on the next page

. Ions that pass through the small aperture enter a second uniform magnetic field of flux density B.
Ions of different mass are separated because they follow different paths as shown in Figure 4.

Figure 4

box

Ions of mass m and charge q travelling at speed v follow a circular path in the uniform magnetic field.

box

Show that the radius r of the circular path is given by

r = mv
Bq

[1 mark]

. The ions of different mass are deflected and strike the detector surface at different distances from the small aperture as shown in Figure 4.

A singly-charged lithium ion (6Li+) passes through the small aperture.

Calculate the distance between the small aperture and the point where this ion strikes the detector surface.

v = 1.5 × 105 m s−1
B = 0.12 T
mass of 6Li+ ion = 1.0 × 10−26 kg

[2 marks]

distance = m

Question 3 continues on the next page

Turn over ►

. Figure 5 shows a different type of mass spectrometer working with lithium ions.

Figure 5

A stationary 7Li+ ion in the lithium sample is at the mid-point between the parallel electrodes. The 7Li+ ion accelerates towards aperture P.

box

Determine the speed of the ion when it emerges through aperture P. mass of 7Li+ ion = 1.2 × 10−26 kg

[3 marks]

speed = m s−1

. 6Li+ and 7Li+ ions are produced in the sample simultaneously and travel a distance L
3 3
from aperture P to the detector.
For each type of ion, the time interval between production and detection is measured.

Discuss how the masses of the ions can be deduced from the measurement of these time intervals.

outside the box

[2 marks]

Turn over for the next question

Turn over ►

box

*21*

Figure 6 shows an oscilloscope connected across resistor R which is in series with an ac supply. The supply provides a sinusoidal output of peak voltage 15 V.

Figure 6

box

. Calculate the rms voltage of the supply.
[1 mark]

rms voltage = V

Question 4 continues on the next page

*17*

Turn over

Do not write outside the

Figure 7 shows the trace of the waveform displayed on the oscilloscope.

Figure 7

Do not write
outside the box

. Determine the y-voltage gain of the oscilloscope used for Figure 7.
[1 mark]

y-voltage gain = V div−1

. A dc supply gives the same rate of energy dissipation in R as the ac supply in
Figure 6.

Draw the trace of the output of the dc supply on Figure 7. The oscilloscope settings remain the same.
[1 mark]

Do not write outside the

. The ac supply shown in Figure 6 is replaced with a square-wave generator operating between 0 and +15 V.

Figure 8 shows the trace of the new waveform displayed on the oscilloscope. The time-base is set to 5.0 × 10−4 s div−1.

Figure 8

Do not write
outside the box

Calculate the frequency of the square waves.
[1 mark]

frequency = Hz

Question 4 continues on the next page

0 4 . 5

Figure 9 shows the arrangement with the square-wave generator connected to an
RC circuit.
A capacitor C is placed in series with the resistor R. The oscilloscope is connected across the capacitor C.

Figure 9

The capacitor charges and discharges.

Figure 10 shows the trace of the waveform displayed on the oscilloscope. The settings of the oscilloscope remain the same as in Question 04.4.

box

Figure 10

Deduce the time constant for the RC circuit, explaining each step of your method.
[3 marks]

box

time constant = s

. State and explain a change to one control setting on the oscilloscope that would reduce the uncertainty in the value of the time constant.
[2 marks]

Turn over ►

Figure 11 shows alpha particles all travelling in the same direction at the same speed. The alpha particles are scattered by a gold (197Au) nucleus.

box

The path of alpha particle 1 is shown.

Figure 11

. State the fundamental force involved when alpha particle 1 is scattered by the nucleus in Figure 11.
[1 mark]

. Draw an arrow at position X on Figure 11 to show the direction of the rate of change in momentum of alpha particle 1
[1 mark]

. Suggest one of the alpha particles in Figure 11 which may be deflected downwards with a scattering angle of 90°

box

[2 marks]
alpha particle number =

. Alpha particle 4 comes to rest at a distance of 5.5 × 10−14 m from the centre of the
197Au nucleus.

Calculate the speed of alpha particle 4 when it is at a large distance from the nucleus. Ignore relativistic effects.

mass of alpha particle = 6.8 × 10−27 kg
[3 marks]

speed = m s−1

Question 5 continues on the next page

. The nuclear radius of 197Au is 6.98 × 10−15 m.

Calculate the nuclear radius of 107Ag.

[2 marks]

box

. All nuclei have approximately the same density.
State one conclusion about the nucleons in a nucleus that can be deduced from this fact.
[1 mark]

A thermal nuclear reactor uses enriched uranium as its fuel.
This is fuel in which the ratio of U-235 to U-238 has been artificially increased from that found in naturally-occurring ore.

box

. Describe what happens when neutrons interact with U-235 and U-238 nuclei in a thermal nuclear reactor.
[3 marks]

. The amounts of U-235 and U-238 in the ore decrease due to radioactive decay at different rates.

A sample of uranium ore today contains 993 g of U-238
The mass of U-238 in this sample was greater 2.00 × 109 years ago.

Show that the mass of U-238 in this sample at that time was about 1.4 kg.

decay constant of U-238 = 1.54 × 10−10 year−1
[2 marks]

Question 6 continues on the next page

Turn over ►

. A thermal nuclear reactor requires a minimum of 3.0% of its uranium mass to be
U-235

The ratio of U-235 to U-238 in the ore has changed over time.
2.00 × 109 years ago, the sample in Question 06.2 contained 52 g of U-235

Deduce whether the sample had a high enough U-235 content to be used in a reactor
2.00 × 109 years ago.

box

[1 mark]

END OF SECTION A

Section B

Each of Questions 07 to 31 is followed by four responses, A, B, C and D. For each question select the best response.

box

0 7 When an ideal gas at a temperature of 27 °C is suddenly compressed to one quarter of its volume, the pressure increases by a factor of 7

What is the new temperature of the gas?
[1 mark]

A 15 °C

B 47 °C

C 171 °C

D 252 °C

Turn over for the next question

*27*

Turn over ►

The diagram shows two flasks X and Y connected by a thin tube of negligible volume.

box

The flasks contain an ideal gas.

The volume of X is twice the volume of Y. When X is at a temperature of 100 K and Y is at a temperature of 400 K there is no net transfer of particles between the flasks.

X contains gas of mass m.

What is the mass of gas in Y?
[1 mark]

m
A 8

m
B 2

C 2m

D 8m

0 9 A sample P of an ideal gas contains 1 mol at an absolute temperature T.
A second sample Q of an ideal gas contains 2 mol at an absolute temperature 2T.
3

box

The total molecular kinetic energy of P is E.

What is the total molecular kinetic energy of Q?

A 2 E
3

B 3 E
4

C 4 E
3

D 3 E
2

[1 mark]

1 0 An ideal gas is contained in a cubical box of side length a. The gas has N molecules each of mass m.

What is the pressure exerted by the gas on the walls of the box?

[1 mark]

mNa3
A
2

× crms2

mNa
B
2

mN × c

crms2

2

C 3a2

rms

mN × c 2
D 3a3 rms

Turn over ►

1 1 Which statement is true about an experiment where Brownian motion is demonstrated using smoke particles in air?

box

[1 mark]

A The experiment makes it possible to see the motion of air molecules.

B The motion is caused by the collisions of smoke particles with each other.

C The motion is caused by collisions between air molecules and smoke particles.

D The motion occurs because air is a mixture of gases and the molecules have different masses.

1 2 The graph shows how the gravitational potential V varies with the vertical distance d from the surface of the Earth.

What does the gradient of the graph represent at the surface of the Earth?
[1 mark]

A potential energy

B mass of the Earth

C magnitude of the gravitational constant

D magnitude of the gravitational field strength

What is the angular speed of a satellite in a geostationary orbit around the Earth?

[1 mark]

box

A 1.2 × 10−5 rad s−1

B 7.3 × 10−5 rad s−1

C 4.4 × 10−3 rad s−1

D 2.6 × 10−1 rad s−1

Two fixed charges of magnitude +Q and +3Q repel each other with a force F. An additional charge of −2Q is given to each charge.

What are the magnitude and the direction of the force between the charges?
[1 mark]

Magnitude of force Direction of force

A F

3
repulsive

B
5F
attractive

C
5F
repulsive

D F

3
attractive

Turn over for the next question

At a distance L from a fixed point charge, the electric field strength is E and the electric potential is V.

What are the electric field strength and the electric potential at a distance 3L from the charge?

box

[1 mark]

Electric field strength Electric potential

A E

3 V

9

B E

3 V

3

C E

9 V

3

D E

9 V

9

Which diagram shows lines of equipotential in steps of equal potential difference near an isolated point charge?

box

[1 mark]

A B

C D

A B C D

Turn over ►

7 A positive charge of 2.0 × 10−4 C is placed in an electric field at a point where the potential is +500 V.

box

What is the potential energy of the system?
[1 mark]

A 1.0 × 10−1 J

B 1.0 × 10−1 J C−1

C 4.0 × 10−7 J

D 4.0 × 10−7 J C−1

1 8 Two charges P and Q are 100 mm apart.
X is a point on the line between P and Q where the electric potential is 0 V.

What is the distance from P to X?
[1 mark]

A 33 mm

B 40 mm

C 60 mm

D 67 mm

9 An uncharged capacitor is connected to a power supply which supplies a constant current of 10 μA.

After 100 ms, the potential difference across the capacitor is 5.0 kV.

box

What is the capacitance of the capacitor?
[1 mark]

A 2.0 × 10−10 F

B 4.0 × 10−10 F

C 2.5 × 109 F

D 5.0 × 109 F

2 0 When a parallel-plate capacitor is connected across a battery, the energy stored in the capacitor is W.

The battery remains connected as the distance between the capacitor plates is halved.

What is the energy now stored in the capacitor?
[1 mark]

A 0.5W

B W

C 2W

D 4W

Turn over for the next question

Turn over ►

A parallel-plate capacitor is made using a sheet of dielectric material between, and in contact with, two plates.
The properties of four sheets of dielectric material are shown.

box

Which sheet will produce the maximum capacitance?

Sheet Relative permittivity Thickness / mm
A 2 0.40
B 3 0.90
C 4 1.0
D 6 1.6

A 10 μF capacitor stores 4.5 mJ of energy. It then discharges through a 25 Ω resistor.

What is the maximum current during the discharge of the capacitor?

[1 mark]

[1 mark]

A 1.2 A

B 18 A

C 30 A

D 36 A

2 3 The diagram shows a current I in a vertical square coil. The coil can rotate about an axis OO’.
The plane of the coil is at right angles to a uniform horizontal magnetic field of flux density B.

box

Which statement is correct?
[1 mark]

A The forces on the vertical sides of the coil are equal in magnitude and opposite in direction.

B A non-zero couple acts on the coil.

C No forces act on the horizontal sides of the coil.

D The forces on all sides of the coil act toward the centre of the coil.

Turn over for the next question

Turn over ►

The diagram shows a small rectangular coil falling between two magnetic poles.

box

The coil is shown at four instants as it passes through the magnetic field.

At which instant will the induced emf be a maximum?
[1 mark]

A B

C D

A B C D

2 5 An alternating emf is induced in a coil rotating in a magnetic field.

What is the phase difference between the magnetic flux linkage through the coil and the emf?

box

[1 mark]

A 0

Turn over for the next question

Turn over ►

The diagram shows the variation with time t of the magnetic flux density B of the field linking a coil.

Which graph shows the variation of induced emf ε in the coil during this time interval?
[1 mark]

box

A B

C D

A B C D

7 A coil P is connected to a cell and a switch.

A closed coil Q is parallel to P and is arranged on the same axis.

box

Which describes the force acting on Q after the switch is closed?
[1 mark]

A steady and directed to the left

B steady and directed to the right

C short-lived and directed to the left

D short-lived and directed to the right

2 8 A point source emits gamma radiation. The intensity I of the radiation is measured at different distances d from the source.

Which graph will show a straight line through the origin?
[1 mark]

A I plotted against d B I plotted against d 2 C I plotted against d −1 D I plotted against d−2

Turn over for the next question

Turn over ►

2 9 The number of parent nuclei in a sample of a radioactive element is N at time t. The radioactive element has a half-life t1
2
The rate of decay is proportional to

[1 mark]

box

A N

B t

1
C t

D t1
2

The table shows the masses of three particles.

Particle Mass / u
proton 1.00728
neutron 1.00867
nucleus of lithium 7Li 7.01436

What is the mass difference of a 7Li nucleus?
[1 mark]

A 4.99841 u

B 0.04216 u

C 0.04147 u

D 0.04077 u

3 1 The mass of the fuel in a fission reactor decreases at a rate of 6.0 × 10−6 kg hour−1.

box

What is the maximum possible power output of the reactor?
[1 mark]

A 75 MW

B 150 MW

C 300 MW

D 9000 MW

END OF QUESTIONS

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*47*

IB/M/Jun20/7408/2

outside the box

For confidentiality purposes, all acknowledgements of third-party copyright material are published in a separate booklet. This booklet is published after each live examination series and is available for free download from www.aqa.org.uk.

Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright-holders may have been unsuccessful and AQA will be happy to rectify any omissions of acknowledgements. If you have any queries please contact the Copyright Team.

IB/M/Jun20/7408/2

*206A740 /2*

IB/M/Jun20/7408/2

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