9702_s11_qp_42
A paper of Physics, 9702
Questions:
12
Year:
2011
Paper:
4
Variant:
2
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1
State what is meant by a field of force. 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: Two protons are isolated in space. Their centres are separated by a distance R. Each proton may be considered to be a point mass with point charge. Determine the magnitude of the ratio force between protons due to electric field force between protons due to gravitational field . ratio =
18. Electric fields  →  18.1. Electric fields and field lines
13. Gravitational fields  →  13.1. Gravitational field
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2
For Examiner’s Use State what is meant by a mole. Two containers A and B are joined by a tube of negligible volume, as illustrated in . container A 3.1 × 103 cm3 17 °C container B 4.6 × 103 cm3 30 °C The containers are filled with an ideal gas at a pressure of 2.3 × 105 Pa. The gas in container A has volume 3.1 × 103 cm3 and is at a temperature of 17 °C. The gas in container B has volume 4.6 × 103 cm3 and is at a temperature of 30 °C. Calculate the total amount of gas, in mol, in the containers. amount = mol
15. Ideal gases  →  15.1. The mole
15. Ideal gases  →  15.2. Equation of state
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3
For Examiner’s Use A capacitor consists of two metal plates separated by an insulator, as shown in . metal plate insulator metal plate 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 . V / V Q / mC Explain why the capacitor stores energy but not charge. For Examiner’s Use Use to determine the capacitance of the capacitor, capacitance = μF the loss in energy stored in the capacitor when the potential difference V is reduced from 10.0 V to 7.5 V. energy = mJ For Examiner’s Use Three capacitors X, Y and Z, each of capacitance 10 μF, are connected as shown in . A B Z Y X Initially, the capacitors are uncharged. A potential difference of 12 V is applied between points A and B. Determine the magnitude of the charge on one plate of capacitor X. charge = μC
19. Capacitance  →  19.2. Energy stored in a capacitor
19. Capacitance  →  19.1. Capacitors and capacitance
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For Examiner’s Use The first law of thermodynamics may be expressed in the form ΔU = q + w. Explain the symbols in this expression. + ΔU + q + w State what is meant by specific latent heat. Use the first law of thermodynamics to explain why the specific latent heat of vaporisation is greater than the specific latent heat of fusion for a particular substance.
14. Temperature  →  14.3. Specific heat capacity and specific latent heat
16. Thermodynamics  →  16.2. The first law of thermodynamics
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5
For Examiner’s Use A bar magnet is suspended vertically from the free end of a helical spring, as shown in . V helical spring magnet coil 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 . 0.5 1.0 1.5 2.0 2.5 t / s V State Faraday’s law of electromagnetic induction. For Examiner’s Use Use Faraday’s law to explain why 1. there is a reading on the voltmeter, 2. this reading varies in magnitude, 3. the reading has both positive and negative values. Use to determine the frequency f0 of the oscillations of the magnet. f0 = Hz The magnet is now brought to rest and the voltmeter is replaced by a variable frequency alternating current supply that produces a constant r.m.s. current in the coil. The frequency of the supply is gradually increased from 0.7 f0 to 1.3 f0, where f0 is the frequency calculated in . On the axes of , sketch a graph to show the variation with frequency f of the amplitude A of the new oscillations of the bar magnet. 0.7 f0 A f0 1.3 f0 f For Examiner’s Use Name the phenomenon illustrated on your completed graph of . State one situation where the phenomenon named in is useful.
20. Magnetic fields  →  20.5. Electromagnetic induction
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For Examiner’s Use An alternating current supply is connected in series with a resistor R, as shown in . R 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). For the current in the resistor R, determine the frequency, frequency = Hz the r.m.s. current. r.m.s. current = A For Examiner’s Use To prevent over-heating, the mean power dissipated in resistor R must not exceed 400 W. Calculate the minimum resistance of R. resistance = Ω
21. Alternating currents  →  21.1. Characteristics of alternating currents
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7
For Examiner’s Use State what is meant by the de Broglie wavelength. An electron is accelerated in a vacuum from rest through a potential difference of 850 V. Show that the final momentum of the electron is 1.6 × 10–23 N s. Calculate the de Broglie wavelength of this electron. wavelength = m For Examiner’s Use Describe an experiment to demonstrate the wave nature of electrons. You may draw a diagram if you wish.
22. Quantum physics  →  22.3. Wave-particle duality
24. Medical physics  →  24.2. Production and use of X-rays
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8
For Examiner’s Use State what is meant by the binding energy of a nucleus. Show that the energy equivalence of 1.0 u is 930 MeV. Data for the masses of some particles and nuclei are given in . mass / u proton neutron deuterium (2 1H) zirconium (97 40Zr) 1.0073 1.0087 2.0141 97.0980 Use data from and information from to determine, in MeV, the binding energy of deuterium, binding energy = MeV For Examiner’s Use the binding energy per nucleon of zirconium. binding energy per nucleon = MeV
23. Nuclear physics  →  23.1. Mass defect and nuclear binding energy
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9
Describe the structure of a metal wire strain gauge. You may draw a diagram if you wish. A strain gauge S is connected into the circuit of . – + R R RF RF +9 V +4.5 V –9 V V2 VOUT strain gauge S 1.0 kΩ V1 The operational amplifier (op-amp) is ideal. The output potential VOUT of the circuit is given by the expression VOUT = RF R × (V2 – V1). State the name given to the ratio RF R . For Examiner’s Use The strain gauge S has resistance 125 Ω when not under strain. Calculate the magnitude of V1 such that, when the strain gauge S is not strained, the output VOUT is zero. V1 = V In a particular test, the resistance of S increases to 128 Ω. V1 is unchanged. The ratio RF R is 12. Calculate the magnitude of VOUT . VOUT = V
6. Deformation of solids  →  6.1. Stress and strain
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11
For Examiner’s Use 11 The use of ionospheric reflection of radio waves for long-distance communication has, to a great extent, been replaced by satellite communication. State and explain two reasons why this change has occurred. 1. 2. The radio link between a geostationary satellite and Earth may be attenuated by as much as 190 dB. Suggest why, as a result of this attenuation, the uplink and downlink frequencies must be different.
8. Superposition  →  8.1. Stationary waves
8. Superposition  →  8.3. Interference
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12
For Examiner’s Use 12 The signal-to-noise ratio in an optic fibre must not fall below 24 dB. The average noise power in the fibre is 5.6 × 10–19 W. Calculate the minimum effective signal power in the optic fibre. power = W The fibre has an attenuation per unit length of 1.9 dB km–1. Calculate the maximum uninterrupted length of fibre for an input signal of power 3.5 mW. length = km Suggest why infra-red radiation, rather than ultraviolet radiation, is used for long-distance communication using optic fibres.
24. Medical physics  →  24.2. Production and use of X-rays
24. Medical physics  →  24.1. Production and use of ultrasound
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