科目：物理 Physics (9702)
年份：2011 夏季
试卷：Paper 42
总页数：20
章节：12-13: Circular Motion & Gravitational Fields, 14-16: Temperature, Ideal Gases & Thermodynamics, 17: Oscillations, 18: Electric fields, 19: Capacitance, 20: Magnetic fields, 21: Alternating currents, 22: Quantum physics, 23: Nuclear physics, 24: Medical physics, 25: Astronomy and cosmology
4 Section A Answer all the questions in the spaces provided. For Examiner's Use 1 (a) State what is meant by a field of force. ........................................................................................................................... [1] (b) Gravitational fields and electric fields are two examples of fields of force. State one similarity and one difference between these two fields of force. similarity: ........................................................................................................................... difference: ........................................................................................................................... .........................................................................................................
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2 (a) State what is meant by a *mole*.
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(b) Two containers A and B are joined by a tube of negligible volume, as illustrated in Fig. 2.1.
<div style="text-align: center;">
</div>
Fig. 2.1
The containers are filled with an ideal gas at a pressure of $2.3 \times 10^5 \, \text{Pa}$ .
The gas in container A has volume $3.1 \times 10^3 \, \text{cm}^3$ and is at a temperature of $6 3 A capacitor consists of two metal plates separated by an insulator, as shown in Fig. 3.1. <div style="text-align: center;">  </div> Fig. 3.1 The potential difference between the plates is $V$. The variation with $V$ of the magnitude of the charge $Q$ on one plate is shown in Fig. 3.2. <div style="text-align: center;">  </div> Fig. 3.2 (a) Explain why the capacitor stores energy but not charge. ............................................................................................................................... ............................................................................................................................... .......................................................................................
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(b) Use Fig. 3.2 to determine
(i) the capacitance of the capacitor,
$$
\text{capacitance} = \underline{\hspace{3cm}} \, \mu\text{F} \, [2]
$$
(ii) the loss in energy stored in the capacitor when the potential difference $V$ is reduced from 10.0V to 7.5V.
$$
\text{energy} = \underline{\hspace{3cm}} \, \text{mJ} \, [2]
$$
For Examiner’s Use
© UCLES 2011 9702/42/M/J/11 [Turn over
Note: The blank lines in the equations are represented as underscores to indicate missing or to be filled in by the examiner. The "For Examiner’s Use" label is placed to the right of the equations as in the original image. The footer information is preserved as is.8
(c) Three capacitors X, Y and Z, each of capacitance $10\,\mu\text{F}$ , are connected as shown in Fig. 3.3.
<div style="text-align: center;">
</div>
Fig. 3.3
Initially, the capacitors are uncharged.
A potential difference of 12V is applied between points A and B.
Determine the magnitude of the charge on one plate of capacitor X.
charge = _________________________ $\mu\text{C}$ [3]
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© UCLES 2011 9702/42/M/J/11
*For Examiner’s Use*9 4 (a) The first law of thermodynamics may be expressed in the form $$ \Delta U = q + w. $$ Explain the symbols in this expression. + $\Delta U$ ............................................................................................................... + $q$ ....................................................................................................................... + $w$ ....................................................................................................................... [3] (b) (i) State what is meant by specific latent heat. ............................................................................................................................... ...............................................................................................
10 5 A bar magnet is suspended vertically from the free end of a helical spring, as shown in Fig. 5.1. <div style="text-align: center;">  </div> Fig. 5.1 One pole of the magnet is situated in a coil. The coil is connected in series with a high-resistance voltmeter. The magnet is displaced vertically and then released. The variation with time $t$ of the reading $V$ of the voltmeter is shown in Fig. 5.2. <div style="text-align: center;">  </div> Fig. 5.2 (a) (i) State Faraday’s law of electromagnetic induction. ............................................................................................................................... ..................................................................................................
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(ii) Use Faraday’s law to explain why
1. there is a reading on the voltmeter,
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2. this reading varies in magnitude,
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3. the reading has both positive and negative values.
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(b) Use Fig. 5.2 to determine the frequency $f_0$ of the oscillations of the magnet.
$$
f_0 = \text{........................................ Hz [2]}
$$
(c) The magnet is now brought to rest and the voltmeter is replaced by a variab12 (d) (i) Name the phenomenon illustrated on your completed graph of Fig. 5.3. ................................................................................................................... [1] (ii) State one situation where the phenomenon named in (i) is useful. ................................................................................................................... [1] For Examiner’s Use © UCLES 2011 9702/42/M/J/11
13 BLANK PAGE Please turn over for Question 6. © UCLES 2011 9702/42/M/J/11 [Turn over
14 6 An alternating current supply is connected in series with a resistor R, as shown in Fig. 6.1. <div style="text-align: center;">  </div> Fig. 6.1 The variation with time $t$ (measured in seconds) of the current $I$ (measured in amps) in the resistor is given by the expression $$ I = 9.9 \sin(380t). $$ (a) For the current in the resistor R, determine (i) the frequency, frequency = ……………………………… Hz [2] (ii) the r.m.s. current. r.m.s. current = ……………………………… A [2] © UCLES 2011 9702/42/M/J/11 For Examiner’s Use
15 (b) To prevent over-heating, the mean power dissipated in resistor R must not exceed 400W. Calculate the minimum resistance of R. resistance = ……………………………… Ω [2] For Examiner’s Use © UCLES 2011 9702/42/M/J/11 [Turn over Note: The vertical line on the right side of the page is not included in the Markdown as it is a layout element and not textual content. The instruction to "For Examiner’s Use" is placed as a note on the right side as per the image. The footer information is included at the bottom.
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7 (a) State what is meant by the de Broglie wavelength.
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(b) An electron is accelerated in a vacuum from rest through a potential difference of 850 V.
(i) Show that the final momentum of the electron is $1.6 \times 10^{-23} \, \text{N} \, \text{s}$ .
[2]
(ii) Calculate the de Broglie wavelength of this electron.
wavelength = ........................................ m [2]
For Examiner’s Use
© UCLE17 (c) Describe an experiment to demonstrate the wave nature of electrons. You may draw a diagram if you wish. For Examiner’s Use ............................................................................................................ ............................................................................................................ ............................................................................................................ ............................................................................................................ ............................................................................................................ [5] © UCLES 2011 9702/42/M/J/11 [Turn over
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8 (a) State what is meant by the *binding energy* of a nucleus.
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(b) Show that the energy equivalence of $1.0\,\text{u}$ is $930\,\text{MeV}$ .
[3]
(c) Data for the masses of some particles and nuclei are given in Fig. 8.1.
<table>
<tr>
<th></th>
<th>mass/u</th>
</tr>
<tr>
<td>proton</td>
<td>1.0073</td>
</tr>
<tr>
<td>neutron</td>
<td>1.0087</td>
</tr>
<tr>
19 (ii) the binding energy per nucleon of zirconium. binding energy per nucleon = …………………………… MeV [3] For Examiner’s Use © UCLES 2011 9702/42/M/J/11 [Turn over
20 Section B Answer all the questions in the spaces provided. For Examiner's Use 9 (a) Describe the structure of a metal wire strain gauge. You may draw a diagram if you wish. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (b) A strain gauge S is connected into the circuit of Fig. 9.1.  Fig. 9.1 T
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(ii) The strain gauge S has resistance 125 Ω when not under strain.
Calculate the magnitude of $V_1$ such that, when the strain gauge S is not strained, the output $V_{OUT}$ is zero.
$$
V_1 = \underline{\hspace{5cm}} \text{ V [3]}
$$
(iii) In a particular test, the resistance of S increases to 128 Ω. $V_1$ is unchanged.
The ratio $\frac{R_F}{R}$ is 12.
Calculate the magnitude of $V_{OUT}$ .
$$
V_{OUT} = \underline{\hspace{5cm}} \text{ V [2]}
$$
For Examiner’s Use
© UCLES 2011 9702/42/M/J/11 [Turn over22 10 Explain briefly the main principles of the use of magnetic resonance to obtain diagnostic information about internal body structures. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... .............
23 11 The use of ionospheric reflection of radio waves for long-distance communication has, to a great extent, been replaced by satellite communication. (a) State and explain two reasons why this change has occurred. 1. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... 2. ............................................................................................................................... ..........................................................