P510/2

Physics

Paper 2

2 ½ hours

July/August 2019 KAYUNGA SECONDARY SCHOOLS EXAMINATIONS COMMITTEE (KASSEC)

JOINT MOCK 2019

PHYSICS

PAPER TWO

2 HOURS 30 MINUTES

INSTRUCTION TO CANDIDATES

• Answer five questions, taking at least one from each of the sections, A , B , C and D but not more than one question should be chosen from either A or B.
• Non-programmable scientific calculators may be used.

Assume where necessary;

• Acceleration due to gravity, g,    =    9.81ms–2
• Speed of light in a vacuum, C    =    3.0×108ms–1
• Electron charge, e            =    1.6×10–19 C
• Electron mass            =    9.11x 10–31 kg
• Plank’s constant, h            =    6.6×10–34 Js
• Permeability of free space µ0    =    4.0px10-7 Hm–1
• Permittivity of free space e0    =    8.85×10–12 Fm – 1
• The constant             =    9.0×10–19F – 1m
• One electron volt (eV)        =    1.6×10–19 J
• A vogadro’s number NA        =    6.02 x 1023mol-1
• Resistivity of Nichrome wire at 250C =    1.2×10– 6Ωm
• Specific heat capacity of water    =    4.2x 103Jkg–1 K-1

SECTION A

1.(a)    (i)    Define a real image.                                (01 mark)

(ii)    With the aid of a diagram show how an image is formed by a plane mirror                                                        (02 marks)

(b)    Explain with the aid of a labelled diagram how a thick plane mirror forms multiple     images.                                        (04 marks)

(c)    Describe how the focal length of a converging lens can be determined using a plane mirror and the non parallax method.                            (04 marks)

(d)    An object is placed 60cm from a convex lens of focal length 15cm and the image is formed on the screen. If a diverging lens is placed half way between the converging lens and the screen, the screen has to be moved 5cm further to obtain a clear image. Calculate the focal length of the diverging lens.                 (05 marks)

(e)    With the aid of diagrams explain the terms critical angle and total internal reflection.                                                (04 marks)

2.(a)    (i)    Define refractive index of a material.                    (01 mark)

(ii)    Describe the adjustments that have to be made before the spectrometer can be used.                                        (04 marks)

(b)    (i)    Describe with the aid of a labelled diagram, the structure and operation of a simple     projection lantern.                                (04 marks)

(ii)    A projection lantern is used to project an image of dimensions 80cm x 98cm onto a screen placed 10.0cm from the projection lens. The dimensions of the slide are 2.0cm x dcm. If the distance of the slide from the projection lens is 26.0cm, find the value of d.                                (03 marks)

(c)    (i)    What is meant by magnifying power of an optical instrument?    (01 mark)

(ii)    Derive an expression for the magnifying power of an astronomical     telescope in normal adjustment.                                    (04 marks)

(d)    Find the separation of the eye piece and objective of an astronomical telescope of magnifying power 20 and in normal adjustment, if its eye piece has a focal length of 5cm.                                            (03 marks)

SECTION B

3.(a)    Define the following terms as applied to sound.

(i)    a harmonic                                    (01 mark)

(ii)    an overtone                                    (01 mark)

(b)    (i)    Describe the motion of air in a tube closed at one end and vibrating in its         fundamental mode.                                    (03 marks)

(ii)    A cylindrical pipe of length 30cm is closed at one end. The air in the pipe         resonates with a tuning fork of frequency 825Hz sounded near the open end of the pipe. Determine the mode of vibration of air in the pipe.                (03 marks)

(Take the speed of sound in air as 330ms – 1)

(c)    (i)    What is meant by the term beats?                    (01 mark)

(ii)    An observer moving between two identical stationary sources of sound along a straight line hears beats at a rate of 5.0s-1. If the frequencies of the sources are 600Hz and the velocity of sound in air is 330ms – 1, Calculate the velocity at which the observer is moving.                            (04 marks)

(d)    (i)    State the principle of super position of waves.                (01 mark)

(ii)    Explain using the principle of superposition of waves the formation of     stationary waves.                                (03 marks)

(e)    State three differences between sound and light waves.            (03 marks)

4.(a)    Explain the formation of fringes by transmission gratings.            (05 marks)

(b)    Given the diffraction grating and a spectrometer, describe how you would use them to measure the wave length of light from a given source.                (07 marks)

(c)    A diffraction grating of 500 lines per mm is illuminated normally with light of wave length 5.26 x 10– 7m. Find the total number of images seen.                (04 marks)

(d)    (i)    State the principle of super position of waves.                (01 mark)

(ii)    Explain how an interference pattern is formed.                (03 marks)

SECTION C

5.(a)    State the laws of electromagnetic induction.                    (02 marks)

(b)    Describe a method of measuring the magnetic flux density in a region between the poles of a magnet.                                        (06 marks)

(c)    A coil of 500 turns and mean area 4.0 x 10 – 2 m2 is rotated at a uniform rate of 600 revolutions per minute about an axis perpendicular to a uniform magnetic field of flux density 0.2T. Calculate the maximum value of the e.m.f induced in the coil.                                                    (04 marks)

(d)    (i)    With the aid of a diagram, describe how a simple d.c motor works.    (06marks)

(ii)    Explain the significance of back e.m.f in the operation of a d.c motor.                                                    (02 marks)

6.(a)    Define the following

(i)    magnetic meridian,                                (01 mark)

(ii)    angle of dip                                    (01 mark)

(b)    An air craft is flying horizontally at 1000kmh – 1 at a point where the earth’s magnetic flux density is 2.4 x 10 – 5 T and the angle of dip is 800. If the distance between the wing tips is 60m, calculate the potential difference induced between the wing tips.                                                        (04 marks)

(c)    Describe with the aid of a diagram an absolute method of determining resistance.                                                (05 marks)

(d)    (i)    What is meant by the terms self induction and mutual induction?    (2marks)

(ii)    Explain the main precautions taken in the construction of an a.c transformer.                                                (03 marks)

(e)    A small rectangular coil of 12 turns and dimensions 5cm by 3cm is suspended inside a long solenoid of 1200 turns per metre so that its plane lies along the axis of the solenoid. The coil is connected in series with the solenoid. The coil deflects through 400 when a current of 3.0A is passed through the solenoid. Find the tortion constant of the suspension.                                         (04 marks)

7.(a)    (i)    Determine the terms peak value and root mean square value of an     alternating     voltage.                                    (02 marks)

(b)     (ii)    An electric kettle draws 3000W from a 240V supply. Find the peak value of     the current drawn by the kettle if the voltage is sinusoidal.        (03 marks)     Bulbs A and B have the same rating. A is connected in series with a capacitor across an a.c source while B is connected in series with an identical capacitor across a d.c source of e.m.f equal to the root mean square voltage of the a.c as shown in the figure above.

Explain why bulb A lights continuously while bulb B does not.            (05 marks)

(c)    (i)    What is meant by the term reactance?                    (01 marks)

(ii)    Derive an expression for the reactance of an inductor of inductance, L when a     sinusoidally varying a.c of frequency, f passes through it.        (4marks)

(iii)    Explain why on average the power delivered to an inductor in one cycle is     zero.                                                (03 marks)

(d)    Explain why a moving coil ammeter is un suitable for measuring alternating current.                                                (02 marks)

SECTION D

8.(a)    (i)    Define capacitance and dielectric constant.                (02 marks)

(ii)    A parallel plate capacitor is connected across a battery and charged fully.         When a dielectric material is now inserted between its plates, the amount    of charge stored in the capacitor changes. Explain the change.        (4 marks)

(b)    A capacitor filled with a dielectric is charged and then discharged through a galvanometer which gives a deflection, q1. The dielectric is then withdrawn half way and the capacitor charged to the same voltage and discharged through the galvanometer again. The galvanometer deflection noted is q2. Show that the dielectric constant
er of the dielectric is given by;

er =                                     (6 marks)

(c)    Explain briefly how a charged capacitor can be fully discharged.        (02 marks)

(d) 3µF

12V

1µF 5µF

A battery of e.m.f 12V is connected across a system of capacitors as shown in the figure above.

Find the,

1. Charge stored on the 3µF capacitor,                         (03 marks)
2. Energy stored in the 5µF capacitor                        (03 marks)

9.(a)    (i)    Define electric field intensity and electric potential.            (02 marks)

(ii)    Derive an expression for the electric potential at a point a distance, r from         a fixed charge.                                    (04 marks)

(b)    (i)    Explain with the aid of a diagram how an insulated metal sphere can be             charged by induction using a negatively charged rod.                (03 marks)

(ii)    Describe how a gold leaf electroscope can be used to detect the presence             of charge on a body.                                (02 marks)

(c)    With the aid of a diagram describe an experiment to show that excess charge resides only on the outside surface of a hollow conductor.                    (05 marks)

(d)    Two metal plates 20cm apart are connected to a 4KV d.c supply. When a small         charged sphere of mass 8.0 x 10 – 3kg is placed between the plates, it remains stationary. Indicate the forces acting on the sphere and determine the     magnitude of the charge on the sphere.                                        (04 marks)

10.(a)    What is meant by the terms e.m.f and internal resistance of a cell?        (02 marks)

(b)    Describe using a diagram, how you would standardize a potentiometer.     (3marks)

(c)    A d.c source of e.m.f 20V and negligible internal resistance is connected in series with two resistors of 500Ω and R ohms. When a voltmeter is connected across the 500Ω resistor it reads 5.0V while it reads 6.0V when connected across a resistor of R ohms. Find the;

(i)    resistance of the voltmeter                            (06 marks)

(ii)    value of R                                    (01 marks)

(d)    (i)    Define temperature coefficient of resistance of a conductor        (01 marks)

(ii)    A coil of wire has resistance of 30Ω at 200C and 34.5Ω at 600C.                     Calculate its temperature coefficient of resistance.            (04 marks)

(e)    Explain why semi – conductors have negative temperature coefficient of     resistance.                                                    (03 marks)

END