9702_s23_qp_41
A paper of Physics, 9702
Questions:
10
Year:
2023
Paper:
4
Variant:
1
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1
Define gravitational field. Define electric field. State one similarity and one difference between the gravitational potential due to a point mass and the electric potential due to a point charge. similarity: difference: An isolated uniform conducting sphere has mass M and charge Q. The gravitational field strength at the surface of the sphere is g. The electric field strength at the surface of the sphere is E. Show that M Q = α g E where α is a constant. Show that the numerical value of α is 1.35 × 1020 kg2 C–2. Assume that the Earth is a uniform conducting sphere of mass 5.98 × 1024 kg. The surface of the Earth carries a charge of – 4.80 × 105 C that is evenly distributed. Use the information in to determine the electric field strength at the surface of the Earth. Give a unit with your answer. electric field strength = unit State how the direction of the electric field at the surface of the Earth compares with the direction of the gravitational field.
18. Electric fields  →  18.5. Electric potential
13. Gravitational fields  →  13.4. Gravitational potential
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2
A steel sphere of mass 0.29 kg is suspended in equilibrium from a vertical spring. The centre of the sphere is 8.5 cm from the top of the spring, as shown in . 8.5 cm spring steel sphere, mass 0.29 kg The sphere is now set in motion so that it is moving in a horizontal circle at constant speed, as shown in . 10.8 cm path of sphere r 27° The distance from the centre of the sphere to the top of the spring is now 10.8 cm. Explain, with reference to the forces acting on the sphere, why the length of the spring in is greater than in . The angle between the linear axis of the spring and the vertical is 27°. Show that the radius r of the circle is 4.9 cm. Show that the tension in the spring is 3.2 N. The spring obeys Hooke’s law. Calculate the spring constant, in N cm–1, of the spring. spring constant = N cm–1 Use the information in to determine the centripetal acceleration of the sphere. centripetal acceleration = m s–2 Calculate the period of the circular motion of the sphere. period = s
6. Deformation of solids  →  6.1. Stress and strain
13. Gravitational fields  →  13.2. Gravitational force between point masses
12. Motion in a circle  →  12.1. Kinematics of uniform circular motion
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3
State the reason why two objects that are at the same temperature are described as being in thermal equilibrium. shows the variations with temperature of the densities of mercury and of water between 0 °C and 100 °C. density temperature / °C mercury density temperature / °C water Temperature may be measured using the variation with temperature of the density of a liquid. Suggest why, for measuring temperature over this temperature range: mercury is a suitable liquid water is not a suitable liquid. A beaker contains a liquid of mass 120 g. The liquid is supplied with thermal energy at a rate of 810 W. The beaker has a mass of 42 g and a specific heat capacity of 0.84 J g–1 K–1. The beaker and the liquid are in thermal equilibrium with each other at all times and are insulated from the surroundings. shows the variation with time t of the temperature of the liquid. temperature / °C t / s State the boiling temperature, in °C, of the liquid. temperature = °C Determine the specific heat capacity, in J g–1 K–1, of the liquid. specific heat capacity = J g–1 K–1 The experiment in is repeated using water instead of the liquid in . The mass of liquid used, the power supplied, and the initial temperature are all unchanged. The specific heat capacity of water is approximately twice that of the liquid in . The boiling temperature of water is 100 °C. On , sketch the variation with time t of the temperature of the water between t = 0 and t = 60 s. Numerical calculations are not required.
14. Temperature  →  14.2. Temperature scales
14. Temperature  →  14.3. Specific heat capacity and specific latent heat
14. Temperature  →  14.1. Thermal equilibrium
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4
State two of the basic assumptions of the kinetic theory of gases. An ideal gas has amount of substance n. The gas is initially in state X, with pressure 2p and volume V. The gas is cooled at constant volume to state Y, with pressure p. The gas is then heated at constant pressure to state Z, with volume 2V. Finally, the gas returns at constant temperature to state X. Determine an expression for the temperature T of the gas in state X, in terms of n, p and V. Identify any other symbols that you use. On , sketch the variation with volume of pressure for the gas as the gas undergoes the three changes. The state X is labelled. Label states Y and Z. pressure volume V 2V p 2p X During the change of state from Y to Z, the increase in internal energy of the gas is U. During the change of state from Z to X, the work done on the gas is W. Complete Table 4.1 to indicate, for each of the three changes of state, the increase in internal energy of the gas, the thermal energy transferred to the gas and the work done on the gas, in terms of p, V, U and W. Table 4.1 change increase in internal energy of gas thermal energy transferred to gas work done on gas X to Y Y to Z +U Z to X +W
15. Ideal gases  →  15.2. Equation of state
16. Thermodynamics  →  16.2. The first law of thermodynamics
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5
Part of an electric circuit is shown in . VIN VOUT 14 kΩ C missing component The circuit is used to produce half-wave rectification of an alternating voltage of potential difference (p.d.) VIN. The output p.d. across the 14 kΩ resistor is VOUT. A component is missing from the circuit of . Complete the circuit diagram in by adding the circuit symbol for the missing component, correctly connected. A capacitor C is shown in the circuit of . State the effect on VOUT of including the capacitor in the circuit. shows the variation with time t of VIN. VIN / V 0.02 0.04 0.06 0.08 t / s 2.5 –2.5 –5.0 –7.5 5.0 7.5 shows the variation with t of VOUT. VOUT / V 0.02 0.04 0.06 0.08 t / s 2.5 7.5 5.0 Determine the frequency of VIN. frequency = Hz Show that the time constant τ for the discharge of the capacitor through the resistor is 0.038 s. Calculate the capacitance of C. Give a unit with your answer. capacitance = unit The circuit of is modified so that it produces full-wave rectification of an input voltage. Suggest, with a reason, how VOUT now varies with time when VIN is as shown in .
19. Capacitance  →  19.3. Discharging a capacitor
21. Alternating currents  →  21.2. Rectification and smoothing
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6
State what is meant by a magnetic field. A long, straight wire P carries a current into the page, as shown in . wire P current into page On , draw four field lines to represent the magnetic field around wire P due to the current in the wire. A second long, straight wire Q, carrying a current of 5.0 A out of the page, is placed parallel to wire P, as shown in . wire P current into page wire Q current 5.0 A out of page The flux density of the magnetic field at wire Q due to the current in wire P is 2.6 mT. Calculate the magnetic force per unit length exerted on wire Q by wire P. force per unit length = N m–1 State the direction of the force exerted on wire Q by wire P. The flux density of the magnetic field at wire P due to the current in wire Q is 1.5 mT. Determine the magnitude of the current in wire P. Explain your reasoning. current = A
20. Magnetic fields  →  20.2. Force on a current-carrying conductor
20. Magnetic fields  →  20.4. Magnetic fields due to currents
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7
State what is meant by the de Broglie wavelength. shows a glass tube in which electrons are accelerated through a high p.d. to form a beam that is incident on a thin graphite crystal. filament cathode anode vacuum fluorescent screen glass tube high p.d. collimator electron beam graphite crystal – + (not to scale) After passing through the graphite crystal, the electrons reach the fluorescent screen. The screen glows where the electrons strike it. shows the fluorescent screen viewed end-on, from the right-hand side of . State the name of the phenomenon demonstrated by the pattern shown in . Explain what can be concluded from the pattern in about the nature of electrons. The electrons in are now accelerated through a greater potential difference between the cathode and the anode. On , sketch the pattern that is now seen on the fluorescent screen in . Explain, with reference to de Broglie wavelength, the change in the pattern on the fluorescent screen.
22. Quantum physics  →  22.3. Wave-particle duality
24. Medical physics  →  24.2. Production and use of X-rays
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8
Table 8.1 shows some data relating to the properties of air, gel and body tissue. The data are given to three significant figures. Table 8.1 material density / kg m–3 speed of sound / m s–1 specific acoustic impedance / kg m–2 s–1 air gel tissue 1.68 × 106 Show that the specific acoustic impedance of gel is 1.68 × 106 kg m–2 s–1. Complete Table 8.1 by calculating the missing values to three significant figures. Use the space below for any working that you need. Use the information in to calculate the intensity reflection coefficient for: an air–tissue boundary intensity reflection coefficient = a gel–tissue boundary. intensity reflection coefficient = Use your answers in to explain why gel is applied to the skin during ultrasound scanning.
24. Medical physics  →  24.1. Production and use of ultrasound
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9
Carbon-11 is radioactive and decays by β+ emission to form boron-11. Carbon-11 has a half-life of 20 minutes. Boron-11 is stable. Define half-life. A sample contains N0 nuclei of carbon-11 and no other nuclei at time t = 0. On , sketch the variation with t of the number of nuclei of boron-11 in the sample. number of nuclei t / min 1.0 N0 0.5 N0 Explain, with reference to the random nature of radioactive decay, why the activity of the carbon-11 sample in decreases with time. State, with reasons, whether a radiation detector placed near to the sample of carbon-11 indicates a measured count rate from the sample that is less than, the same as or greater than the activity of the sample.
23. Nuclear physics  →  23.2. Radioactive decay
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10
State Hubble’s law. Identify any symbols that you use. A star of luminosity 3.8 × 1031 W is a distance of 1.8 × 1024 m from the Earth. Calculate the radiant flux intensity at the Earth of the radiation emitted by the star. radiant flux intensity = W m–2 The star in is in a distant galaxy. A spectral line in the light from this galaxy is known to have a wavelength of 486 nm. This spectral line in the light from the galaxy observed on the Earth has a wavelength of 492 nm. Explain why the wavelength observed on the Earth is different from the wavelength that the galaxy is known to have emitted. Determine a value for the Hubble constant H0. H0 = s–1
25. Astronomy and cosmology  →  25.3. Hubble’s law and the Big Bang theory
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