科目：物理 Physics (9702)
年份：2017 冬季
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, 19: Capacitance, 20: Magnetic fields, 21: Alternating currents, 22: Quantum physics, 23: Nuclear physics, 24: Medical physics
4 Answer all the questions in the spaces provided. 1 (a) State (i) what may be deduced from the difference in the temperatures of two objects, ............................................................................................................................... ............................................................................................................................... [1] (ii) the basic principle by which temperature is measured. ............................................................................................................................... ............................................................................................................................... [1] (b) By reference to your answer in (a)(ii), explain why two thermomet
5 (ii) In practice, there are energy losses to the surroundings. The actual variation with time $t$ of the temperature $\theta$ of the block is shown in Fig. 1.1.  Fig. 1.1 1. Use the information in (i) to draw, on Fig. 1.1, a line to represent the temperature of the block, assuming no energy losses to the surroundings. [1] 2. Using Fig. 1.1, calculate the total energy loss to the surroundings during the heating process. energy loss = ................................................... J 2 © UCLES 2017 9702/43/O/N/17 [Turn over
6 2 (a) State, by reference to simple harmonic motion, what is meant by *angular frequency*. ............................................................................................................................ [1] (b) A thin metal strip is clamped at one end so that it is horizontal. A load of mass $M$ is attached to its free end. The load causes a displacement $s$ of the end of the strip, as shown in Fig. 2.1. <!-- Image: clamp, metal strip, load mass M --> Fig. 2.1 The load is displaced vertically and then released. The load oscillates. The variation with the acceleration $a$ of the displacement $s$ of the load is shown in Fig. 2.2. <!-- Image: s/cm vs a/m s⁻² graph --> Fig. 2.2 © UCLES 2017 9702/43/O/N/17
7 (i) Use Fig. 2.2 to determine 1. the displacement of the load before it is made to oscillate, displacement = ……………………………………… cm 2. the amplitude of the oscillations of the load. amplitude = ……………………………………… cm [2] (ii) Show that the load is undergoing simple harmonic motion. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... [3] (iii) Calculate the frequency of oscillation of
8 3 (a) Define gravitational field strength. ............................................................................................................................ [1] (b) Explain why, for changes in vertical position of a point mass near the Earth’s surface, the gravitational field strength may be considered to be constant. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ [2] (c) The orbit of the Earth about the Sun is approximately circular with a radius
9 4 A coaxial cable is frequently used to connect an aerial to a television receiver. Such a cable is illustrated in Fig. 4.1.  Fig. 4.1 (a) Suggest two functions of the copper braid. 1. ............................................................................................................................... 2. ............................................................................................................................... [2] (b) Suggest two reasons why a wire pair is not usually used to connect the aerial to the receiver. 1. ............................................................................................................................... 2. ......................................................................................
10 5 (a) (i) State Coulomb’s law for the force between two point charges. ............................................................................................................................ [1] (ii) Two point charges are situated in a vacuum and separated by a distance $R$. The force between the charges is $F_C$. On Fig. 5.1, sketch a graph to show the variation of the force $F$ between the charges with separation $x$ for values of $x$ from $x = R$ to $x = 4R$.  Fig. 5.1 [3] (b) Two coils C and D are placed close to one another, as shown in Fig. 5.2.  Fig. 5.2 © UCLES 2017 9702/43/O/N/17
11 The variation with time $t$ of the current $I$ in coil C is shown in Fig. 5.3. On Fig. 5.4, show the variation with time $t$ of the e.m.f. $E$ induced in coil D for time $t = 0$ to time $t = t_5$ . Fig. 5.3 Fig. 5.4 4 © UCLES 2017 9702/43/O/N/17 [Turn over
12 6 Two capacitors P and Q, each of capacitance $C$, are connected in series with a battery of e.m.f. 9.0 V, as shown in Fig. 6.1. Fig. 6.1 A switch S is used to connect either a third capacitor T, also of capacitance $C$, or a resistor R, in parallel with capacitor P. (a) Switch S is in position X. Calculate (i) the combined capacitance, in terms of $C$, of the three capacitors, capacitance = ………………………………………… [2] (ii) the potential difference across capacitor Q. Explain your working. potential difference = ………………………………………… V [2] © UCLES 2017 9702/43/O/N/17
13 (b) Switch S is now moved to position Y. State what happens to the potential difference across capacitor P and across capacitor Q. capacitor P: ............................................................................................................ .................................................................................................................... .................................................................................................................... capacitor Q: ............................................................................................................ .................................................................................................................... ..........................................................
14 7 The circuit of an amplifier incorporating an ideal operational amplifier (op-amp) is shown in Fig. 7.1. Fig. 7.1 (a) By reference to the properties of an ideal op-amp, (i) explain why point P is referred to as a *virtual earth*, ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [4] (ii) derive an expression, in terms of th
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(b) In the circuit of Fig. 7.1, the ratio $\frac{R_2}{R_1}$ is 4.5.
The variation with time $t$ of the input potential $V_{IN}$ is shown in Fig. 7.2.
Fig. 7.2
On Fig. 7.2, show the variation with time $t$ of the output potential $V_{OUT}$ . 3
© UCLES 2017 9702/43/O/N/17 [Turn over16
8 A thin slice of conducting material is placed normal to a uniform magnetic field of flux density $B$, as shown in Fig. 8.1.
<div style="text-align: center;">
</div>
Fig. 8.1
The magnetic field is normal to face CDEF and to face PQRS.
A current $I$ passes through the slice and is normal to the faces CDQP and FERS.
A potential difference, the Hall voltage $V_H$, is developed across the slice.
(a) State the faces between which the Hall voltage $V_H$ is developed.
........................................................................................................... and ........................................................................................................... [1]
(b) The current $I$ is produced by charge carriers, each of charge $+q$17
(ii) Use your answer in (b)(i) and an expression for the current $I$ in the slice to derive the expression
$$
V_H = \frac{BI}{ntq}.
$$
Explain your working.
[2]
(c) Suggest why the Hall voltage is difficult to detect in a thin slice of copper.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... 2
© UCLES 2017 9702/43/O/N/17 [Turn over18 9 (a) In computed tomography (CT scanning), it is necessary to take a series of many X-ray images. Outline briefly the principles of CT scanning. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ..
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(b) A student creates a model for CT scanning.
A section is divided into four voxels, with pixel numbers A, B, C and D, as shown in Fig. 9.1.
<table>
<tr>
<td>A</td>
<td>B</td>
</tr>
<tr>
<td>D</td>
<td>C</td>
</tr>
</table>
$\leftarrow V_1$
$\uparrow V_3$
$\leftarrow V_2$
$\nearrow V_4$
Fig. 9.1
The section is viewed from four different directions $V_1$ , $V_2$ , $V_3$ and $V_4$ , as shown in Fig. 9.1.
The detector readings for each direction are noted and then summed. The result is shown in Fig. 9.2.
<table>
<tr>
<td>47</td>
<td>59</td>
</tr>
<tr>
<td>44</td>
<td>32</td>
</tr>
</table>
Fig. 9.2
The background count is 26.
Determine the pixel numbers A, B, C and D as shown in Fig. 9.1.
A ……………………………… B ……………………………
D ……………20 10 (a) The mean value of an alternating current is zero. Explain why heating occurs when there is an alternating current in a resistor. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) Transmission of electrical energy is frequently achieved using alternating high voltages. Suggest why (i) high voltages are used,
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11 (a) State what is meant by a *photon*.
...............................................................................................................................
............................................................................................................................... [1]
(b) Indium-123 ( $^{123}_{49}\text{In}$ ) is radioactive.
A nucleus of indium-123 emits a $\gamma$ -ray photon of energy 1.1 MeV.
Determine, for this $\gamma$ -radiation,
(i) the frequency,
frequency = ................................................ Hz [2]
(ii) the momentum of a photon.
momentum = ................................................ N s [2]
(c) The indium-123 nucleus is stationary before emission of the $\gamma$ -ray photon.
Use your answer in (b)(ii) to estimate22 12 (a) A radiation detector is placed close to a radioactive source. The detector does not surround the source. Radiation is emitted in all directions and, as a result, the activity of the source and the measured count rate are different. Suggest two other reasons why the activity and the measured count rate may be different. 1. ............................................................................................................................... ............................................................................................................................ 2. ............................................................................................................................... ...........................................................................
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(ii) Use Fig. 12.1 to determine the half-life of the radioactive isotope in the source.
half-life = ………………………………………… hours [4]
(c) The readings in (b) were obtained at room temperature.
A second sample of this isotope is heated to a temperature of $500^\circ \text{C}$ .
The initial count rate at time $t = 0$ is the same as that in (b).
The variation with time $t$ of the measured count rate from the heated source is determined.
State, with a reason, the difference, if any, in
1. the half-life,
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
2. the measured count rate for any specific time.
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
……………………………………………………………………