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P510/2 PHYSICS PAPER 2 MOCKS 2013 2 ½ HOURS TURKISH LIGHT ACADEMY UGANDA ADVANCED CERTIFICATE OF EDUCATION PHYSICS PAPER TWO 2hours 30minutes INSTRUCTION TO CANDIDATES Answer any five questions, including at least one from each section, but not more than one from either section A or B. Where necessary assume the following constants: Acceleration due to gravity, g = 9.81ms-2 Speed of light in vacuum, c = 3.0 x 108ms-1 Speed of sound in air, v Electronic charge, e = Electronic mass, me = 9.1x10-31kg Permeability of free space, µ0 = 4.0 π x10-7Hm-1 Permittivity of free space, ε0 = 8.85x10-12Fm-1 The Constant 1⁄4πε0 = 340ms-1 = 1.6 x 10-19C 9.0x109F-1m 1 SECTION A 1(a)(i) State the laws of reflection of light. (2 marks) (ii) Light is reflected successively, once in each of two mirrors inclined at an angle β, to each other. Find the deviation produced by the reflections in terms of β. (3 marks) (b) Describe how a sextant can be used determine the angle of elevation of the sun. (5 marks) (c) Describe an experiment to determine the focal length of a concave mirror using the no-parallax method, including a graphical analysis. (6 marks) (d) A concave mirror forms a real image of magnification 3, of an object placed at point A, in front of it. When the object is moved to point B, a virtual image of same magnification is obtained. Find the distance AB. (4 marks) 2(a) Derive the expression for the focal length f, of a thin diverging lens in terms of the object distance u, and the image distance v. (4 marks) (b)(i) Define lateral magnification and angular magnification produced by a lens system. (2 marks) (ii) An object is placed a distance x cm from a convex lens of focal length f cm Find the lateral magnification of the image in terms of x and f. (3 marks) (c) A concave lens of focal length 30cm is arranged co-axially with a convex lens of focal length 18cm. An object 3cm tall is placed distance 60cm from the concave lens, on the side remote from the convex lens. If the lenses are 10cm apart, (i) find the position of the final image, (5 marks) (ii) find the height of the image produced, (4 marks) (iii) using a point object draw a sketch ray diagram to show the image formation. (2 marks) SECTION B 3 (a) (i) (ii) State the principal of surperposition of waves State Huygen’s construction principal. (1 mark) (2 marks) Use Huygen’s principle to show that for light moving from one sin i1 medium to another, = constant. Where i1 and i2 are angles made by the ray in sin i2 media 1 and 2 respectively, the normal. (5 marks) (iii) (b)(i) What is a diffraction grating? (1 mark) 2 (ii) Sodium light of wave lengths 5.890x10-7m and 5.924x10-7m falls normally on a diffraction grating of 500lines per cm. Find the angular deviation between their second order images. (4 marks) (d)(i) Describe how interference fringes are formed in Young’s double slit experiment. (5 marks) (ii) State the necessary geometrical conditions for formation of measurable fringes. (2 marks) 4. (a)(i) Explain how beats are produced. (3 marks) (ii) An observer moving between two identical stationary sources of sound, along the line joining them, hears beats at the rate of 3.0s-1. At what velocity is the observer moving if the frequencies of the sources are 480Hz and the velocity of sound when the observation was 340ms-1. (5 marks) (b)(i) What is meant by resonance? (1 marks) (ii) With the aid of a diagram, describe an experiment to investigate the variation of frequency of a wave in a stretched string with length of the string. (6 marks) (c)(i) With the aid of a suitable diagram, explain the terms fundamental note and overtone as applied to a vibrating wire fixed at both ends.(3 marks) (ii) Explain the significance of overtone in production of music? (2 marks) SECTION C 5.(a) With the aid of diagram, explain the terms angle of dip and magnetic meridian, as applied to the earth’s magnetic field. (4 marks) (b) Sketch the magnetic field pattern around a vertical straight current as wire in the earth’s magnetic field. (2 marks) (c) Describe, using appropriate circuit diagram, an experiment you would perform to investigate the variation of the magnetic flux density at the centre of a circular coil, with the current through the coil. (6 marks) (d) A circular coil of 50 turns and mean radius 0.50m is arranged so that its plane is perpendicular to the magnetic meridian. The coil is connected to a ballistic galvanometer of sensitivity 5.7x104rad.C-1. The total resistance of the coil and the galvanometer is 100Ω. When the coil is rotated through 1800 about a vertical axis, the ballistic galvanometer deflects through 0.8 radians. (i)Calculate the horizontal component of the earth’s magnetic field intensity. (5 marks) (ii)Find the voltage which when applied across a solenoid of 2500 turns per metre and total resistance 5Ω will produce a magnetic 3 field at its centre of the same intensity as that calculated in d(i) above. 6. (a) State the laws of electromagnetic induction. (3 marks) (2 marks) (b) Each turn of a coil of N turns is threaded by a magnetic flux of Ф webers. The total resistance of the coil is R ohms. Derive the expression for the charge which circulates through the coil when the magnetic flux is reduced to zero. (5 marks) (c) A coil of 500 turns is wound tightly around the middle of an air cored solenoid of 1000 turns per metre and mean diameter of 7.0cm. An alternating current of I = 10Cos20πt amperes is passed through the solenoid. Calculate the amplitude of the voltage which develops across the terminals of the coil. (6 marks) (d) Explain the following observations: (i) When a d.c motor is switched on, the initial current decreases to a steady value when the motor is running at a constant speed. (2 marks) (ii)If the motion of a d.c motor is slowed down, the current rises, and then falls again when it is allowed to run freely again. (2 marks) (e) Discuss the factors that determine the maximum emf generated by a dynamo. (3 marks) 7. (a) Define root mean square (rms) voltage and reactance of a capacitor. (2 marks) (b)(i) On the same axes draw graphs to show the variation of voltage across a capacitor and current in the circuit against time, when a capacitor is connected to an a.c supply source. (1 mark) (ii) Explain why current and voltage in b(i) above are out of phase. (2 marks) (ii)Explain the function of a capacitor in a rectifier circuit. (3 marks) (c) A flat circular coil of 700 turns, each of radius 15cm, is rotated at a frequency of 300 revolutions per minute about its diameter, at right angles to a uniform magnetic field of flux density 0.12T. Calculate the: (i) maximum magnetic flux linking the coil. (2 marks) (ii) emf induced in the coil when the plane of the coil makes angle 300 with the magnetic field. (3 marks) (iii) rms value of the emf induced in the coil. (2 marks) (d) With the aid of a diagram describe how the repulsion type of ammeter works. (5 marks) 4 SECTION D 8(a) State Ohm’s law. (1 mark) (b) Two resistance wires A and B have resistances in the ratio 4:5; diameters in the ratio 3:2; and lengths in the ratio 1:2 respectively. When the wires are connected in series across a voltage source, the current supplied is 0.5A. Find the (i) ratio of resistances of the wires. (3 marks) (ii) Current supplied to the source when the resistors are connected in parallel. (4 marks) (c)(i) Describe how a potentiometer is used to determine the emf of a cell. (4 marks) (ii) In the experiment in c(i) above, why is the resistance of the galvanometer not important? (1 mark) (iii) How would the experiment in c(i) above be modified to measure the internal resistance of a cell. (4 marks) (d) A battery of emf 15V and internal resistance 2Ω is connected across an 8Ω resistor. Calculate the (i) rate at which electrical energy is being generated in the battery. (2 marks) (ii) rate of energy dissipation in the resistor. (1 mark) 9(a)(i) Define electric potential energy of a charge. (1 mark) (ii) Derive an expression for the electric potential energy of two point charges of Q1 and Q2 a distance x apart, in air. (4 marks) (b) Three charges of -5x10-9C, +7x10-9C and +6x10-9C are placed at the vertices A,B and D respectively of a rectangle, in air. The rectangle is of sides 3cmx5cm 5 as in the figure above. Calculate the electric field intensity at C. (7 marks) (c)(i) What is an equi-potetial surface? (1 mark) (ii) Show that the electric field intensity is always perpendicular to the equi-potential surface. (2 marks) (d) Describe an experiment to show that charge resides only on the outside surface of a charged hollow conductor. (5 marks) 10(a)(i) Define the terms: Dielectric constant and dielectric strength. (2 marks) (ii) Explain why capacitance changes when a dielectric is placed in a capacitor. (4 marks) (iii) List two other uses of dielectric in a capacitor. (1 mark) (b) A capacitor with a dielectric of relative permittivity εr, between its plates is charged then isolated. (i) Show that when the dielectric is removed from the capacitor, the fractional change in voltage across its plates is εr -1. (4 marks) (ii) If the relative permittivity of the dielectric is 2.3 and the capacitor was initially charged to 35V find the new voltage across the capacitor. (2 marks) (c) The plates of a capacitor of area 4.0cm2 are 3mm apart in air. Find the (i) charge stored in the capacitor when it is charged to 9000V. (3 marks) (ii) energy stored in the capacitor when the area is reduced to half the above value and the capacitor again charged to the same voltage. (4 marks) END 6