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P510/2
PHYSICS
JULY 2017
2½ h

Uganda Advanced Certificate of Education

PHYSICS MOCK EXAMINATION 2017
Paper 2
2 hours 30 minutes
INSTRUCTIONS 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.
Any additional questions will not be marked.
Non-programmable scientific calculators may be used.
Assume where necessary:
Acceleration due to gravity, g = 9.81m s-2
Speed of light in a vacuum, c = 3.0 × 108 m s-1
Electron charge e = 1.6 × 10-19 C
Permeability of free space,  o = 4.0π×10-7 H m-1
Permittivity of free space,  o = 8.85 ×10-12 F m-1
1
The constant, = 9.0 ×109 F-1 m
4 o
Velocity of sound in air at 0ºC = 330 m s-1

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SECTION A
1.(a) Define refractive index of a material. What is the refractive index of a
material through which light travels at 2 × 108 m s-1? (02 marks)
(b) Show that the refractive index, n, of the material of glass prism is given
by
 A + Dm 
sin  
n =  2  where A is the refractive angle of the prism and
 A
sin  
2
Dm is the angle of minimum deviation for light passing through the
prism.
(03 marks)

(c) Describe an experiment to determine the refractive index of glass using

a triangular prism and optical pin s. (05 marks)
(d) A thin equi-convex lens of glass of refractive index 1.50 whose
surfaces have a radius of curvature 24.0 cm is placed on a horizontal
plane mirror. When the space between the lens and the mirror is filled
with a liquid, a pin held 40.0 cm vertically above the lens is found to
coincide with its own image. Calculate the refractive index of the
liquid. (05 marks)

(f) In an experiment to determine focal length of a lens, after tabulating

results, a student plotted graph of magnification m against image
distance, v.
Explain how the student used the graph to find the focal length of the
lens, without calculating the slope. (03 marks)
(g) Explain the advantage of using prisms instead of plane mirrors in
periscopes. (02 marks)
2.(a) Define the terms
(i) Power of accommodation. (02 marks)
(ii) angular magnification , as applied to optical instruments. (1mark)
(b) Explain one disadvantage a Galilean telescope has over an
astronomical telescope. (02 marks)
(i) Power of accommodation. (01mark)
(c) An astronomical telescope has an objective with a focal length of
100 cm and a diameter of 5 cm. If the eyepiece has a focal length of
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20 cm and the telescope is used in normal adjustment, calculate the

(i) Magnifying power (02 marks)
(ii) Diameter of the eye ring (02 marks)
(iii) Separation of the lenses. (0 marks2)

(d) Give two advantages of a prism binoculars as an optical instrument.

(02 marks)
(e) (i) Define chromatic aberration. (01 mark)
(ii) Give two properties of lenses used to make an achromatic doublet.
(02 marks)
(f) Describe an experiment to determine focal length of a diverging lens
using a concave mirror. (05 marks)

SECTION B
3.(a) State the principle of superposition of waves? (01marks)
(b) Distinguish between Progressive and stationary waves.(03marks)
(c) (i) Describe an experiment to determine the velocity of sound in air by
the dust tube method. (06 marks)
(ii) Explain why changes of pressure have no effect on the velocity of
sound in air at constant temperature. (03 marks)
(d) (i) What is meant by the terms resonance and fundamental frequency?
(02 marks)
(ii) A steel wire of length 40 cm and diameter 0.025 cm vibrates
transversely in unison with a tube, open at both ends and of effective
length 60 cm, when each is sounded in its fundamental mode at 270C.
Find the tension in the wire. (05 marks)
4.(a) Distinguish between interference and diffraction of light. (02 marks)
(b) (i) Explain what is meant by path-difference as applied to interference of
two wave motions. (03 marks)
(ii) In Young’s double slit experiment, the 4 bright fringe is formed
th

3.4 mm away from the centre of the fringe system when the
wavelength of light used is 6.3 ×10-7 m.
Calculate the distance of the screen from the slits if the separation of
the two slits is 0.62 mm (03 marks)
(ii) Explain why light is considered to be a transverse wave, while sound
is not. (02 marks)
(c) Two slits X and Y are separated by a distance a and illuminated
With light of wavelength  . Derive the expression for the separation
between successive fringes on a screen placed a distance D from the

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slit. (05 marks)

(d) Explain with the aid of a diagram, how Newton’s rings are formed.
(05 marks)
SECTION C
5.(a) Define the following:
(i) Magnetic flux (01 mark)
(ii) Magnetic flux density, (01 mark)
(iii) Angle of dip (01 mark)

(b) (i) A conductor of length l moving with a velocity v cuts through flux
at an angle  to a uniform magnetic field.
Derive an expression for the e.m.f induced in it. (04 marks)

(ii) Describe with the aid of a diagram, an absolute method of

Measuring resistance.
(c) (i)

X Y

0.8 m
Figure 1
In Figure 1 above, XY is a straight conductor of length 0.8 m and
Mass 3.0 × 10-2 kg. The conductor is suspended by a pair of threads
in a uniform magnetic field of flux density 4.5 × 10-2 T.
Determine the magnitude and direction of the current required to
remove the tension in the suspension threads. (04 marks)
(ii) Explain why a wire carrying current in a magnetic field, moves.
(03 marks)
6.(a) (i) Define eddy currents. (01 mark)
(ii) Explain how eddy currents are put to good use in a car speedometer.
(03 marks)
(iii) Explain the effect of eddy currents in a dynamo and how this is
overcome. (03 marks)
(b) A copper disc of radius 0.06 m with its plane perpendicular to a
uniform magnetic field spins at 900 revolutions per minute about an
axis through its centre. A potential difference of 4.5 × 10-5 V. Is
shown on a voltmeter connected between the axle and the rim.

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Calculate the flux density of the field. (04 marks)

(c) With the aid of a diagram explain how an a.c generator works.
(05 marks)
(d) (i) What is self-induction? (01 mark)
(ii) Describe an experiment to demonstrate self-induction. (03 marks)

7.(a) (i) Define reactance of a capacitor. (01 mark)

(ii) Draw a sketch graph to show the variation of reactance of a
capacitor with frequency when the capacitance is constant. (01 mark)
(ii) A capacitor of capacitance 2  F has a current of 1 × 10-3 A (r.m.s)
flowing through it. The voltage across the capacitor is 0.156 V.
Calculate the frequency of the source. (04 marks)
(b) Explain how alternating current can be converted into fairly steady
direct current by use of diodes. (04 marks)

(c) The diagram in Figure 2 shows a bulb connected to a battery in

Series with a capacitor.
K

Bulb
Figure 2
State and explain what is observed when
(i) the switch K is closed. (02 marks)
(ii) the battery is replaced with a source of alternating current and the
switch closed. (03 marks)
(d) With the aid of labelled diagram explain how a hot wire instrument
works. (05 marks)
SECTION D
8.(a) (i) Define the ohm and state Ohm’s law. (02 marks)
(ii) Explain why potential difference between terminals of a battery is
not always equal to its e.m.f. (02 marks)
(b) Describe an experiment to determine the resistance of a resistor
using a circuit that includes a rheostat. (05 marks)
(c) In a simple metre bridge the resistors A and B have values 5Ω and 3Ω
respectively. When A is shunted by a length of wire, the balance point
is found to be 0.527 m from A. What is the resistance of the shunt?
(03 marks)
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If the shunt wire is 0.75 m long and 0.25 mm in diameter, what is the
resistivity of the material of the wire? (03 marks)
A B

Figure 3
(d) Explain the effect on resistance of a conductor when its cross
sectional area is increased. (03 marks)
(e) Why is a Wheatstone bridge unsuitable for comparing two resistances
that are very small? (02 marks)

9.(a) (i) Define electric potential (01 mark)

(ii) Derive an expression for the electric potential difference between two
points A and B at distances a and b respectively from a single
point positive charge, Q. (04 marks)
(b) Explain how you can show that the potential on a pear shaped
charged conductor is the same at all points. (03 marks)
(c) Three charges of magnitudes + 2.0 × 10 C, + 3.0 × 10-8 C and
-8

−4.0 × 10−8 C are placed at the vertices A,B and C respectively, of

a triangle as shown in figure 4 below.
A

10 cm
10 cm

B 12 cm C
Figure 4
Find
(i) the force exerted on the charge at B. (04 marks)

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(ii) Electric potential at a point D half way between B and C. (04 marks)
(d) Describe an experiment to show that equal and opposite charges are
produced when a body is electrified by rubbing. (04 marks)

10.(a) (i) Define relative permittivity of a material. (01 mark)

(ii) Describe an experiment to determine relative permittivity of a
dielectric using the vibrating reed switch method. (05 marks)
(b) In a vibrating reed experiment, two parallel plates have an area of
0.12 m2 and are separated by a distance of 2 mm by a dielectric.
A battery of 150 V charges and discharges the capacitor at a
frequency of 50 Hz and a current of 20  A is produced.
(i) Calculate the relative permittivity of the dielectric. (03 marks)
(ii) What is the new capacitance if the dielectric is half withdrawn from
the plates? (02 marks)
(c) Figure 5 below shows a charged capacitor with a dielectric of
thickness t between its plates.

+Q

d t

–Q
Figure 5
 0 r A
Show that the effective capacitance is given by C =
 r (d − t ) + t
where  r is the dielectric constant of the material. (05 marks)

(d) (i) Describe and explain what happens when the terminals of a capacitor
are connected to a battery of e.m.f. V. (03 marks)

(ii) Hence draw a graph to show the variation of p.d with time across the
plates of the capacitor. (01 mark)

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END

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