科目：物理 Physics (9702)
年份：2013 夏季
试卷：Paper 43
总页数：20
章节：12-13: Circular Motion & Gravitational Fields, 14-16: Temperature, Ideal Gases & Thermodynamics, 17: Oscillations, 18: Electric fields, 20: Magnetic fields, 21: Alternating currents, 22: Quantum physics, 23: Nuclear physics, 24: Medical physics
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Section A
Answer all the questions in the spaces provided.
For Examiner's Use
1 (a) State what is meant by a gravitational field.
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(b) In the Solar System, the planets may be assumed to be in circular orbits about the Sun. Data for the radii of the orbits of the Earth and Jupiter about the Sun are given in Fig. 1.1.
<table>
<tr>
<th></th>
<th>radius of orbit /km</th>
</tr>
<tr>
<td5
(c) The orbital period of the Earth about the Sun is $T$ .
(i) Use ideas about circular motion to show that the mass $M$ of the Sun is given by
$$
M = \frac{4\pi^2 R^3}{GT^2}
$$
where $R$ is the radius of the Earth’s orbit about the Sun and $G$ is the gravitational constant.
Explain your working.
[3]
(ii) The orbital period $T$ of the Earth about the Sun is $3.16 \times 10^7$ s.
The radius of the Earth’s orbit is given in Fig. 1.1.
Use the expression in (i) to determine the mass of the Sun.
mass = ………………………………………… kg [2]
For Examiner’s Use
© UCLES 2013 9702/43/M/J/13 [Turn over]6 2 (a) State what is meant by an *ideal gas*. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (b) Two cylinders A and B are connected by a tube of negligible volume, as shown in Fig. 2.1. <div style="text-align: center;">  </div> Fig. 2.1 Initially, tap T is closed. The cylinders contain an ideal g
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(ii) Cylinder B has a constant volume of $1.6 \times 10^3 \, \text{cm}^3$ and contains $0.20 \, \text{mol}$ of gas. When tap T is opened, the pressure of the gas in both cylinders is $3.9 \times 10^5 \, \text{Pa}$ . No thermal energy enters or leaves the gas.
Determine the final temperature of the gas.
temperature = ………………………………………… K [2]
(c) By reference to work done and change in internal energy, suggest why the temperature of the gas in cylinder A has changed.
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© UCLES 2013 9702/43/M/J/13 [Turn over
For Examiner’s Use
Note: The vertical text "For Examiner’s Use" is placed on the right margin as per the image. T8 3 A ball is held between two fixed points A and B by means of two stretched springs, as shown in Fig. 3.1. <div style="text-align: center;">  </div> Fig. 3.1 The ball is free to oscillate along the straight line AB. The springs remain stretched and the motion of the ball is simple harmonic. The variation with time $t$ of the displacement $x$ of the ball from its equilibrium position is shown in Fig. 3.2. <div style="text-align: center;">  </div> Fig. 3.2 (a) (i) Use Fig. 3.2 to determine, for the oscillations of the ball, 1. the amplitude, amplitude = ______________________ cm [1] 2. the frequency. frequency = ______________________ Hz [2] © UCLES 2013 9702/43/M/J/13 For Examiner’s Use
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(ii) Show that the maximum acceleration of the ball is $5.2 \, \text{m} \, \text{s}^{-2}$ .
For Examiner's Use
[2]
(b) Use your answers in (a) to plot, on the axes of Fig. 3.3, the variation with displacement $x$ of the acceleration $a$ of the ball.
$\uparrow$
$a / \text{m} \, \text{s}^{-2}$
$\rightarrow$
$x / 10^{-2} \, \text{m}$
Fig. 3.3
[2]
© UCLES 2013
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[Turn over
For Examiner's Use
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© UCLES 2013
9702/43/M/J/13
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© UCLES 2013
9702/43/M/J/13
[Turn over
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© UCLES 2013
9702/43/M/J/13
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© UCLES 2013
9702/43/M/J/13
[Turn over
For Examiner's Use
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© UCLES 2013
9702/43/M/J/13
[Turn over
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© UCLES 2013
9702/43/M/J/13
[Turn ove10 (c) Calculate the displacement of the ball at which its kinetic energy is equal to one half of the maximum kinetic energy. displacement = …………………………… cm [3] For Examiner’s Use © UCLES 2013 9702/43/M/J/13
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4 (a) Define *electric potential* at a point.
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(b) A charged particle is accelerated from rest in a vacuum through a potential difference $V$ . Show that the final speed $v$ of the particle is given by the expression
$$
v = \sqrt{\frac{2Vq}{m}}
$$
where $\frac{q}{m}$ is the ratio of the charge to the mass (the specific charge) of the particle.
[2]
(c) A particle with specific charge $+9.58 \times 112
5 (a) Define the *tesla*.
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(b) A long solenoid has an area of cross-section of $28 \, \text{cm}^2$ , as shown in Fig. 5.1.
Fig. 5.1
A coil C consisting of 160 turns of insulated wire is wound tightly around the centre of the solenoid.
The magnetic flux density $B$ at the centre of the solenoid is given by the expression
$$
B = \mu_0 n I
$$
where $I$ is the current in the sol13 (ii) the flux linkage in the coil C. flux linkage = ……………………………… Wb [2] (c) (i) State Faraday’s law of electromagnetic induction. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………………………………………………………………………………… [2] (ii) The current in the solenoid in (b) is reversed in direction in a time of 0.80 s. Calculate the average e.m.f. induced in coil C. e.m.f. = ……………………………………… V [2] For Examiner’s Use © UCLES 2013 9702/43/M/J/13 [Turn over
14 6 A simple transformer is illustrated in Fig. 6.1. <div style="text-align: center;">  <br/> Fig. 6.1 </div> (a) State (i) why the iron core is laminated, ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) what is meant by an *ideal* transformer. ............................................................................................................................... ............................................
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7 Some data for the work function energy $\phi$ and the threshold frequency $f_0$ of some metal surfaces are given in Fig. 7.1.
<table>
<tr>
<th>metal</th>
<th> $\phi/10^{-19}$ J</th>
<th> $f_0/10^{14}$ Hz</th>
</tr>
<tr>
<td>sodium</td>
<td>3.8</td>
<td>5.8</td>
</tr>
<tr>
<td>zinc</td>
<td>5.8</td>
<td>8.8</td>
</tr>
<tr>
<td>platinum</td>
<td>9.0</td>
<td></td>
</tr>
</table>
Fig. 7.1
(a) (i) State what is meant by the *threshold frequency*.
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8 (a) State what is meant by a nuclear fusion reaction.
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(b) One nuclear reaction that takes place in the core of the Sun is represented by the equation
$$
{}^2_1\text{H} + {}^1_1\text{H} \rightarrow {}^3_2\text{He} + \text{energy}.
$$
Data for the nuclei are given in Fig. 8.1.
<table>
<tr>
<td></td>
<td>mass/u</td>
</tr>
<tr>
<td>proton ${}^1_1\text{H}$ </td>
<td>1.00728</td>
17 Section B Answer all the questions in the spaces provided. For Examiner's Use 9 (a) Suggest electrical sensing devices, one in each case, that may be used to monitor changes in (i) light intensity, ...................................................................................................................[1] (ii) the width of a crack in a welded joint, ...................................................................................................................[1] (iii) the intensity of an ultrasound beam. ...................................................................................................................[1] © UCLES 2013 9702/43/M/J/13 [Turn over
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(b) A student designs the circuit of Fig. 9.1 to detect changes in temperature in the range $0^\circ \text{C}$ to $100^\circ \text{C}$ .
<div style="text-align: center;">
</div>
Fig. 9.1
The resistance of the thermistor is $R_T$ and that of the resistor is $R$ .
The student monitors the potential difference $V_{OUT}$ .
State and explain
(i) whether $V_{OUT}$ increases or decreases as the temperature of the thermistor increases,
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..............................................................................19 10 (a) Distinguish between sharpness and contrast in X-ray imaging. sharpness: ....................................................................................................................... contrast: ....................................................................................................................... ....................................................................................................................... [2] (b) State two causes of loss of sharpness of an X-ray image. 1. ....................................................................................................................... ....................................................................................................................... 2. ............................
20 (ii) Use your answer in (i) to suggest whether an X-ray image of the bone and muscle would show good or poor contrast. ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... [2] For Examiner’s Use © UCLES 2013 9702/43/M/J/13
21 11 A radio station emits an amplitude-modulated wave for the transmission of music. (a) (i) State what is meant by an *amplitude-modulated (AM)* wave. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) Give two reasons why the transmitted wave is modulated, rather than transmitting the information signal directly as a radio wave. 1. .................................................................................................................
22 (b) The variation with frequency $f$ of the amplitude $A$ of the transmitted wave is shown in Fig. 11.1. <div style="text-align: center;">  <br/> Fig. 11.1 </div> For this transmission, determine (i) the wavelength of the carrier wave, wavelength = ……………………………… m [2] (ii) the bandwidth, bandwidth = ……………………………… kHz [1] (iii) the maximum frequency, in Hz, of the transmitted audio signal. frequency = ……………………………… Hz [1] © UCLES 2013 9702/43/M/J/13 For Examiner’s Use Note: The image placeholder (``) is used to represent the figure since actual image extraction is not possible in this context. In a real scenario, you would replace this with the actual image or its description.
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12 An optic fibre is used for the transmission of digital telephone signals. The power input to the optic fibre is 9.8 mW. The effective noise level in the receiver circuit is 0.36 µW, as illustrated in Fig. 12.1.
<div style="text-align: center;">
</div>
Fig. 12.1
The signal-to-noise ratio at the receiver must not fall below 28 dB.
For this transmission without any repeater amplifiers, the maximum length of the optic fibre is 85 km.
(a) Calculate the minimum input signal power to the receiver.
$$
\text{power} = \underline{\hspace{5cm}} \text{ W [2]}
$$
(b) Use your answer in (a) to calculate the attenuation in the fibre.
$$
\text{attenuation} = \underline{\hspace{5cm}} \text{ dB [2]}
$$
(c) Determine the attenuation per unit length of the fibre.
$$
\t