CANDIDATE NO: _____________________________________________________________________________________
CATHOLIC SCHOOLS ACADEMIC UNION (CASAU) 2020
FORM SIX PRE-NATIONAL EXAMINATION
131/3A
PHYSICS 3A
ACTUAL PRACTICAL 3A
(For School Candidates Only)
Friday, 14th February 2020 a.m.
Time: 3:20 Hours
Instructions
1. This paper consists of three (3) questions.
2. Answer all questions.
3. Question Number 1 carries 20 marks and the other two (2) ,15 marks each.
4. Calculations should be clearly shown.
5. Mathematical tables and non-programmable calculators may be used.
6. Cellular phones are not allowed in the examination room
7. Write your Examination Number on every page of your answer booklet(s)
8. Use the following:
Π =3.14
Page 1 of 4
CASAU F.6 -2020
CANDIDATE NO: _____________________________________________________________________________________
1. In this experiment you are required to determine the density of the glass of which the test tube
is made by using the following method.
First determine the initial cross-sectional area Ai, of the test tube.
Do this as follow.
(a) Clamp the test tube vertically with its base resting on the bench. Fill the measuring cylinder
with water up to 100cm3 mark. Pour about 15ml of water from measuring cylinder into the
test tube and record the volume as V.
Also record height h of water level above the base of test tube. Pour another 15ml of water into
the test tube and record the new volume V and new height h of water in the test tube.
Repeat this process so as to obtain at least six different readings V and h
(b) Plot a graph of V as ordinate and h as abscissa and hence deduce the initial cross – sectional
is, Ai of the test tube.
(c) (i) Now, unclamp the test tube and pour its water back into the measuring cylinder. Wind the
wire provided around the test tube so that the turns of wire are close together. Count and
record the number of turns.
(ii) Un winds the wire and find the average length L of one turn of the wire when the wire
has been wound around the test tube.
(iii) Calculate the circumference C of the test tube at the part around which the wire has been
wound. You are given that C  L -  d , where d is the diameter of the wire.
(iv) Determine C for various parts of the test tube and calculate the average circumference C
of the test tube
2
C
Ae 
(v) Hence calculate the external cross-sectional area Ae, of the test tube, where
4
(d) Next, measure the entire length L of the test tube. Given that the volume of the glass of the
test tube is Vg  LA e - A i  ; Calculate Vg.
(e) (i) Finally, weigh the empty test-tube to obtain its mass M.
(ii) Hence determine the density D of the glass of which the test tube is made.
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CASAU F.6 -2020
CANDIDATE NO: _____________________________________________________________________________________
2. The aim of this experiment is to investigate the relation between the rate of loss of heat from a
calorimeter and the temperature excess over its surroundings under condition of forced convection.
Proceed as follows:
(a) Put some water in the beaker and leave it to heat from the burner till the water boils
(b) While the water is boiling, set up the apparatus as shown in figure .1 below where the
calorimeter is placed on the wooden slab provided. Place the stirrer in the appropriate opening
in the lid and cover the calorimeter. Clamp one of the thermometers to pass through the other
opening in the lid so as to be able to read the temperature of water.
(c) When the water in the beaker has boiled, transfer some of it to the calorimeter till the level of
3
water is about full.
4
(d) Read and record the temperature  o C of water at every two minutes intervals, beginning
when the temperature of the water is about 80oC. As the experiment progress, gently stir the
water and fan the calorimeter with some paper. Take your readings for 20 minutes
(e) Using the other thermometer read and record the room temperature at the beginning and the
end of the experiment. Hence record and average room temperature  R .
(f) (i) Plot a graph of Ln (   R ) against time t
(ii) Theoretically the experiment obeys the relation: Ln (   R )  kt  ( a constant)
Determine the value of k and the constant
(iii) What is the physical meaning of k?
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CASAU F.6 -2020
CANDIDATE NO: _____________________________________________________________________________________
3. The aim of this experiment is to determine the resistance per cm, r and resistivity,  of the wire
W provided.
Proceed as follows:
(a) Connect the dry cell E and switch K to the terminal AB of the resistance wire AB Connect the
standard resistor X and Y and the galvanometer G as shown by figure.2 below.
(b) Measure a length Lw =100cm of the wire W and connect it in parallel with a standard resistor
Y.
(c) Close switch K and obtain a balance point D using jockey J. Record the length AD =L and
open K
(d) Repeat the above procedures with length of wire W equal to Lw =80,60,50,40 and 20cm and
in each case record the corresponding value of L
(e) Remove the wire W and obtain the balance point C as described above. Record the length
AC=Lo
(f) Using your reading determine the distances d given by; d=L-Lo. Tabulate your readings
1
against Lw
d
(ii) Measure the diameter of the wire W and hence determine its cross sectional area.
AB r
Given that the gradient G of the graph is G 
ABYL o  YL o 2
(g) (i)Plot a graph of
(h) Calculate the value of r and hence determine the resistivity  of the wire W. Give that
X=1.0Ω
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CASAU F.6 -2020