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Instructions :
❖ This paper consists of 12 pages and 50 questions.
❖ Answer all the questions.
❖ Write your index number in the space provided to you
❖ In each of the questions 1 to 50, pick one of the alternatives from (1),(2), (3), (3), (5) which is correct or most
appropriate and mark your response on the answer sheet with a (X) in accordance with the instructions
01. The variation of rate of decay (A) of a radio active element with time (t) is given by A=A 0 e−
. The dimensions
of A0 would be
(1) T (2)T1−
(3)MT (4)M1−
T (5) DImensionless
02. When the temperature of a metal block is increased by 200C, its volume was increased by 0.12%. The linear
expansivity of the metal would be
(1) 2x 10-5K-1 (2) 4x 10-5K-1 (3) 6 x10-5K-1 (4) 8x 10-5K-1 (5) 1x10-4K-1
03. The graph shows the position of a particle moving
along the x-axis with time. According to the given
graph how many times is the particle momentarily at
rest?
(1) 3 (2) 4 (3) 5
(4) 6 (5) 7
04. During one oscillation of a particle under simple harmonic motion, the particle at two different points will have
(A) The same velocity
(B) The same speed
(C) The same acceleration
(1) (A) only (2) (B) only (3) (C) only
(4) (A) and (B) only (5) (B) and (C) only
05. A charge is uniformly distributed with a surface density of σ, along the surface of an isolated conducting sphere of
radius a. The electric field intensity on the surface of the sphere would be
Calculator is not allowed
(g = 10 N kg-1)
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06. Generally the velocity of sound is higher in solids when compared with the velocity in air, for this solids have high
(1) pressure
(2) temperature
(3) density
(4) elasticity
(5) relative molecular mass
07. A yellow light undergoes minimum deviation when it goes through a prism of prism angle A. At this stage the
incident angle is I, the refraction angle is r and the deviation angle is D. Consider the following statements
regarding this.
(A) A > 2r
(B) 2(I-r) =D
(C) A=2I
(1) Only (A) is true (2) Only (B) is true
(3) Only (C) is true (4) Only (A) and (B) is true
(5) Only (A) and (C) only true
08.
In the above experiment masses m1 and m2 are joined together by a light string and the string goes over a
frictionless light pulley as shown in the figure. The mass m1 is slipping on a frictionless horizontal surface. The
magnitudes of the two masses m1, m2 , the in-between distance d, the speed of the mass m1 when it passes x1 and x2
are measured. For which of the following can this experimental set-up be used?
(A) To explain the conservation of momentum
(B) To explain the conservation of energy
(C) To measure the acceleration due to gravity.
(1) (A) only (2) (B) only (3) (C) only
(4) only (A) and (B) only (5) only (B) and (C)
09. A circular disc with a moment of inertia kgm2 and a radius of 0.1m is placed on top of an inclined plane and
allowed to roll. It rolls without slipping. The angular velocity of the disc after it had completed 5 full rotations was
2rads-1. What is the frictional force given by the plane to the disc?
(1) 2N (2) 4N (3) 5.5N (4) 6.3N (5) 7N
10. If the resistance of a metal rod at 1000C is 40% higher than the resistance of the metal rod at 200C then the
temperature co-efficient of resistance of the rod is given by
200
1)1(
180
1)2(
100
1)3( 60
1)4(
50
1)5(
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11. Two solid spheres of radius a,2a made of the same material are allowed to move freely through a fluid. The terminal
velocity of the small sphere is V0 then the terminal velocity of the large sphere would be
(1) V0 (2) 2V0 (3) 3V0 (4) 4V0 (5) 8V0
12. The maximum and minimum acceleration that a car can have is 5ms-2 and -5ms-2 respectively. The car starts
moving from rest from a point and comes back to rest at a point that is 20m away. The minimum possible time
taken for this would be
(1) 2s (2) 3s (3) 4s (4) 5s (5) 6s
13.
Water is in a thick glass container. Which of the above graphs show the possible path(s) of a monochromatic light
ray incident on the surface of the water?
(1) (X) only (2) (X) and (Y) only (3) (Y) and (Z) only
(4) (X) and (Z) only (5) all (X), (Y)and (Z)
14. Which of the followings is not true about electric and magnetic fields?
(1) Electric force affects a stationary charge in an electric field. But magnetic force doesn’t affect a stationary
charge in the magnetic field.
(2) If a charge is moving in a field where there is electric field and magnetic field, its velocity may remain
unchanged.
(3) If a charge is moving in a field where there is only magnetic field, its velocity may remain unchanged.
(4) A charge that is travelling in a uniform magnetic field, in adirection perpendicular to that of the magnetic field,
will have a constant acceleration.
(5) In a place where there is a uniform electric fied, whatever the direction of the charge may be,its acceleration
will remain unchanged.
15. A block of mass 39kg is placed on a horizontal surface and it is
pulled by using a force F as shown in the figure. The the
coefficient of kinetic friction between the block and the surface is
0.4. if the block is moving with a constant velocity along the
surface, what is the magnitude of the force F?
(1)100N (2)150N (3)200N (4)290N (5)400N
16. A sound source that is at rest emits waves with a wavelength of 34cm. The velocity of sound in air is 340ms-1. If the
sound source starts moving with a constant speed of 20ms-1, what would the wavelength of the wave travelling
forward along the path be?
(1) 68cm (2) 36cm (3) 35cm (4) 34cm (5) 32cm
F
(3/5)F
(4/5)F
(X)
(Y)
(Z)
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17. Parallel plate capacitor filled with air, has been charged to a voltage difference of V and has been isolated. Then the
space between the parallel plates is filled with a substance that has an electric permittivity constant of 4, this
voltage difference will change to
(1) V/4 (2) V/ 2√2; (3) V
(4) 2√2V (5) 4V
18. The maximum power that can be dissipated by an electric wire without it melting is 0.5W and the maximum
current is 2A. If it is cut into two equal pieces, what is the maximum power and current that can be dissipated by
one piece of the electric wire without it melting? ;
(1) 0.5W, 2A (2) 0.25W, 2A (3) 0.25W, 1A (4) 0.5W, 1A (5) 1W, 2A
19. Three identical, uniform metal rods AB, CD and EF are joined together as
shown in the figure (such that the centre of the rods AB and CD are
connected to the rod EF). The end C is kept at a constant temperature of
00C. The ends A, B and D were kept at a constant temperature of 1000C. If
the heat loss to the environment is neglected then at which part of the rod is
the temperature gradient the highest?
(1) AE (2) BE (3) EF
(4) FC (5) FD
20. The change in volume ΔV and the increase in internal energy ΔU that takes place when a specific amount of gas is
supplied with a heat Q at constant pressure is given in the following table.
Q ΔV ΔU
500J 0.001m3(decrease ) 700J
-500J 0.002m3(increase) X
By using the data given in the table, which of the following gives the value of X?
(1) -900J (2) +900J (3) +300J (4) -300J (5) Zero
21. A galvanometer of internal resistance 10Ω is connected to another resistance of 10/19Ω and made into an ammeter
so that it shows full scale deflection for a specific current. Compare to the sensitivity of the galvanometer the
sensitivity of the ammeter will
(1) increase by a factor of 20 (2) increase by a factor of 19
(3) decrease by a factor of 1/20 (4) decrease by a factor of 1/19
(5) remain unchanged
22. A point charge q is moving in a constant external electric field of electric field
intensity E. What is the change in the kinetic energy of the charge q when it
moves from A to B?
(1) Ed (2) 2Ed (3) Eqd
(4) 2Eqd (5) Not enough data
23. Concrete bricks have been piled on a highway so close together that there is no space between them. Due to this
they cannot expand. During a cold season when the temperature is 80C, these bricks were piled in the above
mentioned way for the construction of the highway. What is the stress on the bricks on a hot day, when the
temperature is around 380C? The young’s modulus for the compression of the brick is Y=20x109Nm-2, linear
expansivity is 12x10-5K-1
1000C 1000C
00C 1000C
C
A B
D
F
E
A B
E
d
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(1) 1.2x106 Nm-2 (2) 2.4 x106 Nm-2 (3) 7 x106 Nm-2 (4) 7.2 x106 Nm-2 (5) 7.2 x107 Nm-2
24. A horizontal sonometer wire has been stretched by using a weight that has a mass 100 times the mass of the wire.
At this stage, it takes 0.01s for a transverse impulse to travel from one end of the wire to the other end. If this wire
is vibrating at its first overtone, what is the frequency of this vibration?
(1) 100Hz (2) 200Hz (3) 300Hz (4) 400Hz (5) 500Hz
25.
The figure shows two masses joined together using a light string connected over two pulleys on a wedge that is on a
horizontal plane. All the parts are frictionless. The string is kept taut and the masses are released from rest. The
wedge will
(1) Accelerate towards the left if m1 < m2
(2) Accelerate towards right if m1 < m2
(3) Accelerate towards the left, does not depend on the magnitude of the mass
(4) Accelerate towards the right, does not depend on the magnitude of the mass
(5) Will remain at rest.
26. Two parallel wires P, Q carrying a current IP and IQ respectively is placed in a
surrounding where there is no other field as shown in the figure. The distance between
the wire id d. The magnetic force acting on a unit length of the qire Q is
(1) Towards P
(2) d
II QP
2
0 away from P
(3) Towards P
(4) away from P
(5) Zero
27. A one end closed resonance tube and a both end opened resonance tube Resonate with a tuning fork separately at
their fundamental resonance state. Consider the following statements regarding this.
(A) The length of both of the tubes is equal.
(B) The maximum pressure in air is at the closed end of the one end closed resonance tube
(C) The minimum pressure in air is at the middle of the both end opened resonance tube
Which of the above statements is/are true?
(1) (A) only (2) (B) only (3) (C) only
(4) (A) and (B) only (5) (B) and (C) only
IP IQ
P
P Q
d
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28. A satellite is found on a circular orbit around the earth. After a long period of time, due to air resistance the total
mechanical energy of the satellite decreases by 1J. The kinetic energy of the satellite
(1) Increases by 1J
(2) Remain unchanged
(3) Decreases 0.5 J
(4) Decreases 1 J
(5) Decreases2 J
29.
The particles X, Y and Z are thrown from a point on the ground with the given horizontal vertical velocities. (P), (Q)
and (R) are the possible paths of the particles between the period just before and after the particle reaches the
maximum point. If the path of X between the period just before and after the particle reaches the maximum point is
(P) then what is the path of the particle Y and Z?
(1) (P), (P)
(2) (R), (P)
(3) (R), (Q)
(4) (Q), (Q)
(5) (P), (Q)
30. Which of the following statements is false regarding the fundamental particles? The magnitude of electron charge
is e
(1) up quark (u) , down Quark (d) will have the charges +(2/3)e, -(1/3)e respectively
(2) anti quarks have the magnitude of the charge of the u,d quarks with opposite signs.
(3) Proton has three Quarks uud, and neutron has three Quarks udd.
(4) Baryons are neutrons, protons which have 3 Quarks or antiproton with three anti quarks. Similarly Meson
contains a Quark and an antiquark
(5) Gluon are used to keep quarks together in neutrons and protons and they are charged
31. A soap layer is applied on an end of a capillary tube and the other end of the tube is immersed in water such that
the tube is vertical. As it is immerced in this way, soap bubble is formed at the top end. On which of the following
does the radius of the soap bubble not depend on?
(1) Surface tension of the water
(2) Surface tension of the soap layer
(3) The length of the tube and the depth to which the tube is immersed
(4) Density of the water
(5) Atmospheric pressure
U
V
X
2U
V
Y
U
2V
Z
(P)
(Q)
(R)
u ,
d
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32. The following figures show a rod placed along the principle axis of lenses. In which of the following instances
could the length of the image of the rod be equal to the lengthof the actual rod?
33. A person going on a long journey in a vehicle with closed windows notices water condensing on the inner part of
the glass when he enters a certain region. The suitable reason for this observation would be
(1) The temperature outside the vehicle is higher than the temperature inside the vehicle
(2) The temperature inside the vehicle is higher than the temperature outside the vehicle
(3) The dew point outside the vehicle is higher than the dew point inside the vehicle
(4) The dew point outside the vehicle is higher than the temperature inside the vehicle
(5) The dew point inside the vehicle is higher than the temperature outside the vehicle
34. The breakdown voltage (VZ) of the zener diode in the given
circuit is 4V. if the ideal ammeter shows the reading 3mA,
what is the magnitude of the resistance R?
(1) 1k (2) 2k (3) 3k
(4) 4k (5) 5k
35. A neutron is absorbed by a U235
92 atom and undergoes the following fission process.
nKrBaUn A 1036
13956
23592
10 3++→+
The value of A in the aboe process would be
(1) 90 (2) 91 (3) 92 (4) 94 (5) 95
36. Consider the following statements regarding a compound microscope.
(A) The objective forms an enlarged real image
(B) The eye piece creates an enlarged virtual image
(C) For the normal adjustments of the microscopes made using the same eye piece and obectives with different
focal lengths, in order to obtain the same angular magnification the positions of the objects will be different.
(1)
F
F
2F
2F
(3)
F
F
2F
2F
(5)
F
F
2F
2F
(2)
F
F
2F
2F
(4)
F
F
2F
2F
6V
r=0
A
2k
R
2k
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Which of the above is/are true?
(1) Only (A) (2) Only (A) and (B) (3) Only (A) and (C)
(4) Only (B) and (C) (5) All (A),(B),and (C)
37. I the given electric circuit the internal resistance of the cell can be
neglected. For a specific value of the variable resistance R, the ammeter and
voltmeter reading is 2mA and 5V respectively. When the magnitude of the
variable resistance is decreased, the new reading of the voltmeter and
ammeter
reading of the ammeter 1.5mA 2.5mA 3mA ;2.5mA 1mA
reading of the voltmeter 6V 6V 7.5V 4V 3V
(1) (2) (3) (4) (5)
38. A circular disc of radius r rolls around without slipping in a fixed circular ring of
radius R at a constant angular velocity. The time taken for the disc to go aroung
the ring was T. What is the momentary speed of the point directly opposite to the
point that is in contact with the ring, on the circumference of the disc?
( ) TrR /2)1( +
( ) TrR /22)2( +
( ) TrR /24)3( −
( ) TrR /4)4( −
( ) TrR /4)5( +
39. In the given circuit V is a variable voltage supplied by a
battery. Which of the following graphs correctly shows the
variation of the voltage VX at X relative to the earth with V.
(The internal resistance of both the cells can be neglected.)
40. A light with a wavelength 0
5000 A is incident on a metal surface. The macimum kinetc energy of the emitted
photoelectron is 0.48eV. The work function of the metal would be (hc = 12.4 x103eV0
A )
(1) 1.03eV (2) 1.20eV (3)1.60eV (4) 1.75eV (5) 2.0 eV
41. The H2 gas in a container is separated into two by a metal wall. The gas at the left and the right side are Hot and
cold respectively. Which of the following correctly shows the line vector of the momentum of the H2 molecules
before and after colliding with the wall at steady state?
R
r
V
VX
(1)
V
VX
(2)
VX
(3)
V
VX
(4)
V
VX
(5)
V
r = 0
12V
R0
A
V
R
6V
r = 0
A
R
R
R
V
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42. It is necessary to find the the latent heat of fusion of ice using the method of mixture in an environment where the
room temperature is 300C and the dew point is 260C. In order to correct the heat displacement to the surrounding,
different students use the same experimental equipments plan the experiment such that the temperature fall ()
takes different values. Which of the following correctly shows the variation of the mass of the ice cube with the
planned by the students?
(The mass of the ice cube used can be neglected when compared to the mass of the water)
43.
The breakdown voltage of the zener diode in the above circuit is 5V. AB is a variable resistor of resistance 2 k.
The resistance between A and S has a linear change when the point S is moved from A to B. Which of the following
shows the variation of the voltage at C, VC when S is moved from A to B with respect to the earth?
m
/0C
(1)
2 4 6 8 10 /0C
m
(2)
2 4 6 8 10 /0C
m
(3)
2 4 6 8 10 /0C
m
(4)
2 4 6 8 10 /0C
m
(5)
2 4 6 8 10
A
B
1k
12V
2k
r
S
VZ =5V
C
Hot air
Cool air
(1)
Hot air
Cool air
(2)
Hot air
Cool air
(3)
Hot air
Cool air
(5)
Hot air
Cool air
(4)
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44.
In the above tube system, the position X is always maintained at a constant pressure 2P0. An incompressible non-
viscous fluid is found inside the tube. The points A,B are on the tube have valves such that the air in the
surrounding can enter the tube and that the fluid in the tube cannot exit from it.The lids T1 and T2 are closed in the
instant given in the figure.Take the atmospheric pressure as P0 and the density of the fluid as . Consider the
following statements
(A) When the lid T1 is opened the fluid exits with a speed of
(B) The speed at which the fluid exits when the lid T2 is opened is greater than the speed at which the fluid exits
when the lid T1 is opened
(C) When the lid T2 is opened, Air travels through the valves A, B and through the tubes.
(1) Only (A) is true (2) Only (B) is true
(3) Only (A) and (B) are true (4) Only (A) and (C) are true
(5) all (A), (B) and (C)
45.
A rectangular wave shaped voltage of range 5V is supplied to the input VA of an amplifier with silicon transistor as
shown in the figure. Which of the following graphs show the output voltage VO for this?
VA/V
+5
-5
t
RC = 5k
6V
RB=4k
VA
C
V0
A
VC /V
(3)
B
5
A
VC /V
(5)
B
5
A
VC /V
(4)
B
5
A
VC /V
(2)
B
5
A
VC /V
(1)
B
5
X
A B
T1
T2
fpilf;Fohafs;;
Vertical tubes
Horizontal tube
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46. Consider the following statements regarding the shape of the parts (or the nature) of a mercury in glass
thermometer, the reason for it and its advantage
The shape of the parts
(or the nature ) Reason Advantage
(A) The mercury bulb not being a
spherical shape.
In order to obtain a higher surface
area for a specific volume.
Accuracy increses
(B) The thickness of the bulb being
small
To make the heat flow across the
wall of the bulb easily
Sensitivity increases
(C)
The cross section of the stem
not being a circular shape with
the hole at the centre
In order for the light ray coming
from the mercury column to refract
at the surface of the glass
The mercury column can
be observed clearly
Which of the above is/are correct?
(1) (A) only (2) (B) only (3) (A) and (B) only
(4) (B)and (C) only (5) all (A), (B) and (C)
47. The figure (I) shows a both end closed tube with uniform
hole at room temperature 300C. Two equal parts of dry air is
trapped by a mercury column of height H. This tube is then
held vertically as shown in the figure (II). The temperature
() of the air column at the botton is changed so that the
centre of the tube coincides with the centre of the mercury
column. Which of the following graphs correctly shows the
variation of of the temperature () with the height H of the
mercury column?
/0C
H
30
(1)
/0C
H
30
(2)
/0C
H
30
(3)
/0C
H
30
(4) (5)
/0C
H
30
VO
T
(1)
t
t
VO
(2)
T
VO
(3)
t
VO
(4)
t
t
Vo
(5)
Figure (I)
H
Figure (II)
H
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48. Resistors are connected together using a rigid
conductors and the circuit that is shown is
constructed. Variying magnetic field is found in
a circular region of radius r and 2r perpendicular
to the plane of the paper.in the given directions.
If the magnetic flux density increases increases
at the rate K, the correct relationship between the
currents in the circuits i and I would be
(1) I + i = 0 (2) I - i = 0 (3) 7I + 5i = 0 (4) 7 I - 5i = 0 (5) 5I - 3 i = 0
49.
The figure shows a uniform magnetic field directed outwards to the paper on one side of XY. Identical conducting
rods of length 12l is used to make the stiff frames P, Q and R. Each of them move with a constant velocity V. the
charges that flow through a cross-section of each frame is Qp, Qq and Qr, the correct relationship between these are
(1) Qp = Qq = Qr (2) Qp < Qq < Qr (3) Qp > Qq > Qr (4) Qp = Qr > Qq (5) Qp = Qr < Qq
50. Sand is continuously flowing out of a helicopter with a streamline flow. The helicopter is initially moving to the
right with a constant speed V. It then suddenly turns and starts moving to the left wth a constant speed V. The air
resistance on te san can be neglected. Which of the following shos the shape of the streamline flow of the sand
viewed from the ground? (the black dot denotes the helicopter)
Has a radius r, magnetic flux
densityincreasing at a rate of K,
field directed outwards to the
paper
Has a radius 2r, magnetic flux
densityincreasing at a rate of K,
field directed inards to the paper
;Gyk;
R
R
R
i
I
(1) (2) (3)
(4)
(5)
(P)
(Q)
(R)
X
Y
2l
4l
3l
3l
2l
4l
V
V
V
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[KOg;gjpg;GupikAilaJ/ All Rights Reserved]
AL/2019/01/E-II(A)
For examiner’s use only
Part Question No. Marks
A
1
2
3
4
B
5
6
7
8
9(A)
9(B)
10(A)
10(B)
Total
Percentage
Final marks;
In numbers
In words
Code numbers
Examiner 1
Examiner 2
Checked by
Supervised by
Index No. : …..………………………... This question paper consists of 22 pages.
This paper comprises of two parts A and B. The time allotted for the two parts is three hours only.
Use of calculators is not allowed.
Part A – Structured Essay ( Pages 2 - 9 )
Answer all the questions on the question paper itself.
Write your answers in the space provided for each question.
Please note that the space provided is sufficient for the answer and that extensive answers are not
expected.
Part B – Essay ( Pages 11 - 22 )
This part consists of six questions. Answer four questions only. Use the papers supplied for this
purpose.
At the end of the time allotted for this paper, tie the two papers together so that Part A is on top and
hand them over to the Supervisor.
You are permitted to remove only Part B of the question paper from the Examination Hall.
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AL/2019/01/E-II(A)
Part A- Structured essay Answer all of the questions on this paper itself
(Acceleration due to gravity 𝑔 = 10𝑁𝑘𝑔−1)
01.
(a) The stress vs strain graph of most material will have the following shape. Identify the point A, B in this graph
(b)
(i) When a mass m is hung freely on a string of length l and cross-sectional area A, the extension that took
place was e. Give an equation for the Young’s modulus of the material of the rod in terms of the quantities
given.
…………………………………………………………………………………………………………..……
…………………………………………………………………………………………………………..……
…………………………………………………………………………………………………
(ii) Give the condition range in which the equation that you wrote in (b) (i) is valid ?
…………………………………………………………………………………………………………..
(c) The experimental set-up that is normally used in an experiment to find the Young’s modulus of a cylindrical
wire is given below.
Additional weights (N) are added to the experimental wire and their corresponding additional extension (e) is
measured and a graph is drawn from it.
A : ……………………………………….
B : ……………………………………….
Stress
Strain
A
B
C
Reference wire
Main scale
Stationary load
Vernier scale
Experimental wire
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AL/2019/01/E-II(A)
(i) Find the gradient of the graph
……………………………………………………………………………………………………….…..……
………………………………………………………………………………………………….........………
(ii) What is the measurement that you need to take in order to obtain the cross-sectional area of the
experimental wire? What is the measuring instrument that you can use for this?
…………………………………………………………………………………………..………………..……
…………………………………………………………………………………….......……………..………
(iii) The cross-sectional area of the experimental wire was 1 × 10−6𝑚2and the length of the wire is given as
2m. Find the young’s modulus of the wire.
…………………………………………………………………………………………………………..……
……………………………………………………………………………………………....……...………
…………………………………………………………………………………………………………..……
………………………………………………………………………………………………….......………
(iv) Give two reasons for using the two wires: reference wire and the experimental wire.
1. ……………………………………………………………………...…………………………………
2. ………………………………………………………………………………...………………………
0 05 10 15 20 25 30 35
Additional weight (N)
Additional
extension(mm)
0.1
0.2
0.3
0.4
0.5
●
●
●
●
●
0.7
0.6 P
Q
Page 16
- 4 -
[See page five
AL/2019/01/E-II(A) (v) How will you confirm that the experimental wire did not exceed the proportionality limit?
…………………………………………………………………………………………………………..……
………………………………………………………………......…………………………………..………
(vi) Give reason for why the points P, Q differ from the other points in the graph.
……………………………………………………………………………………………………………..
(vii) A system created for a game is shown in the
figure. Here the motor system is used to move
the system containing the players up and down
using the moving wire along the very long
pillar. It moves up from A to B with a small
constant velocity. Then moves from B to C
under gravity, finally it decelerates from C to A
and comes to rest at A. According to the given
motion, from A to B, B to C and from C to A,
where does the moving wire most likely to
break?
.............................................................................
02. (a) You have been asked to find the latent heat of fusion of ice using the method of mixture. For this you have
been provided with warm water, appropriate calorimeter with stirrer, small ice cubes and blotting paper.
(i) Give another major thing that you would need to carry out this experiment successfully?
…………………………………………………………………………………………………………..…
(ii) Give the experimental procedure that needs to take place when preparing the ice cubes and adding to the
water
Preparing: ……………………….……………………………………………...……….....………
……………………………………………………………………...….………………
Adding to the water ;: ………………………………………………………………….....………....……….
…...…………………………………………………………………………………….
(iii) What is the experimental procedure that needs to be carried out in order to minimize the heat exchange
with the surrounding?
……………………………………………………………………………………..……...…..........................
……………………………………………………………………………………………………...................
.......................................................................................................................................................................
(iv) Assume that you have correctly carried out the experiment and obtained the following readings
Measurements Value
The mass of the calorie meter and the stirrer 150𝑔
The initial mass of the calorie meter, the stirrer and the water 250𝑔
The initial temperature of the system 350𝐶
The final minimum temperature of the system 250𝐶
The final mass of the system 261𝑔
A very long pillar
A
B
C System containing
the players
Motor system
Moving wire
Page 17
- 5 -
[See page six
AL/2019/01/E-II(A) You have been given that the heat capacity of the calorie meter is 40𝐽𝐾−1and the specific heat capacity of
the water is 4 × 103𝐽𝑘𝑔−1𝐾−1.
From the above data find the latent heat of fusion of ice.
………………………………………………………………………………………………..…………..…
…......................................................…………………………………………………………………………
…………………………..…………..……………………………………...……….………………………
……………………………………..………………………………………….………………………………
……...………………………………..………………………..………………………………………………
(b) Instead of the method of mixture, the following set-up can be used to find the latent heat of fusion of ice. Small
ice cubes at melting point are placed in a large funnel. In the experimental process (beaker A), an electric heater
is used and in the controlled process (beaker B), electric heater is not used. Both of the set-ups are identical
Except the electricl heater part. They are placed in the same environment.There is a very small net at the
bottom of the wire. And the melted water is collected in the beakers.
The stop watch is started after confirming that the experimental process is supplied with electricity and the rate at
which water leaves each funnel remains constant separately. The reading of the electronic balance is obtained after
t seconds. The mass of water collected in the beakers after t seconds from the experimental process and from the
controlled process was m1 and m2 respectively. The power of the heater used was P watt.
(i) What is the adjustment that you need to make on the electronic balance when starting the stopwatch?
…………………………………………………………………………………………………………..….........…
………………………………………………………………......………………………………………..….........
(ii) What is the purpose in carrying out this experiment with the experimental process and controlled process?
…………………………………………………………………………………………………………..….........
(iii) Give the expression for the latent heat of fusion of ice cube (L) in terms of 𝑚1, 𝑚2, 𝑃, 𝑡
………………………………………………………………………...…………………………………..….........
…………………………………………………………………………………………………………..….........
m1kg
Connected to the
electricity
Ice cube
beaker𝐴
Melted water
Electonic balance
Electric heater
experimental process
Not Connected to the electricity
beaker𝐵
Ice cube
Electric heater
Melted water
Electronic balance
m2kg
controlled process
Page 18
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[See page seven
AL/2019/01/E-II(A) (iv) If different measurements of m1 and m2corresponding to different time measurements (t) were obtained and a
𝑚1 − 𝑚2 Vs (t) graph is drawn the gradient of the graph was found to be 2𝑔𝑠−1. Find the power of the
heater. (Use the final measurement that you calculated in question (a)(iv)
…………………………………………………………………………………………………………..….........
…………………………………………………………………………………………………………..….........
………………………………………………………..................…………………………………………….
03. You have been provided with an ideal spectrometer, equilateral glass prism and a sodium light source in order to
find the refractive index n of glass. The scale of the spectrometer increases in clockwise direction.
(a)
(i) In what order would you adjust the parts A, B, C and D of the spectrometer.
…………………………………………………………………………………………………………..…....
.…………………………………………………………………………………………………………..…....
(ii) Draw how you would place an equilateral prism on B when adjusting it in the given diagram
(iii) In the experiment carried out to find the prism angle, light
ray is incident on the sides of an equilateral prism and
reflects in the paths P and Q. the corresponding reading are
taken correctly. The reading obtained at the position P is
40050’. What is the possible reading that is obtained at the
position Q?
…………………………………………………………………
………………………………………..….........………………
(iv) What are the two measurements that need to be taken to find the minimum deviation angle of the light ray
through the prism?
1. ………………………………………………………………………………………………………
2. ………………………………………………………………………………………………………
𝐷
P Q
Page 19
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[See page eight
AL/2019/01/E-II(A) (v) If the two measurements that you obtained in (iv) are 143029’ and 180041’ then find the minimum deviation
angle. ( assume that when taking the measurements the scale doesn’t go through 3600)
…………………………………………………………………………………………………………..….......
(vi) By taking the prism angle as 600 find the refractive index of the glass. (take sin 48036′ = 0.75)
(b) By using the spectrometer, you have been asked to find the deviation angle (d) of the prism for different
values of incident angle (i) and draw a graph that shows the variation of d with i. The light ray coming from
the part D of the spectrometer is incident on the surface of the prism at O. This ray gets refracted, travels
through the prism and emerges out from the prism. The ray that emerges is observed by using the part A of
the spectrometer and the reading Z is taken. The part of the light ray that gets reflected at O is also observed
by using the part A of the spectrometer and the reading X is taken. The prism is removed from the prism table
and the reading Y is taken
(i) Give the expression for the incident angle (i) and the deviation angle (d) in terms of X, Y and Z.
…………………………………………………………………………………………………………..….......
…………………………………………………………………………………………………………..….......
…………………………………………………………………………………………………………..….......
(ii) Draw the I Vs. d graph that you obtained in the following axis, Denote the minimum deviation angle D.
(iii) Comparing with the above curve, draw the graph that you would obtain if you use a green colour light
instead of a sodium light source and label it as G
X
Y Z
d
i
Page 20
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[See page nine
AL/2019/01/E-II(A) 04. (a)The figure shows a potentiometer circuit. In the circuit E is cell with an electromotive force E and negligible
internal resistance. And a variable resistance R is connected to the circuit.
What is the use of a variable resistance R in a potentiometer circuit?
……………………………………………………………………………..............……………………………
.(b) The following circuit is constructed to find the nature of a zener diode using a potentiometer circuit. The voltmeter
and all the mili-ammeter are ideal. The breaking voltage of zener diode used here is 5V
The touch key connected to the end X is placed such that it is in contact with the potentiometer circuit and is
allowed to slide from the end Q to the end P. QO =l
(i) When the touch key is in contact with the potentiometer between PQ, is the zener diode at forward bias
or reverse bias?
……………………………………………………………………………………………………………
(ii) Give the readings of the mili-ammeter A1 and A2, when the reading of the voltmeter is found to be 6V.
……………………………………………………………………………………………………………
…………………………………………………………………………………………………………..
(iii) Find the readings of the mili-ammeter A1 and A2, when the reading of the voltmeter is found to be 9V.
……………………………………………………………………………………………………………
…………………………………………………………………………………………………………..
…………………………………………………………………………………………………………….
(iv) Draw a graph showing the variation of the reading of the mili-ammeter( 𝐴1) with the distance QO(l)
𝐴1
𝑙
r=0
( 𝐸 𝑅
𝑆
P Q
)
r=0
( 𝐸 𝑅
𝑆
P Q
)
K
O
V
1k
V
mA 𝐴2
Y V
𝐴1 𝑉𝑍 = 5𝑉
mA
mA
2k
X V
Page 21
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AL/2019/01/E-II(A) .(c) The following circuit is constructed in a way to find the work function of a material using a potentiometer
circuit. A light source S emits white light beams and a colour filter is used to send blue colour light beams to
the cathode.
(i) The touch key connected to the end A of the photoelectric cell is kept so that it is in contact with the
potentiometer wire and is moved from the end Q to P step by step. What will happen to the reading of the
mili-ammeter during this?
………………………………………………………………………………………………………..
(ii) The ends of the cell E are reversed and again the touch key is moved from the end Q to P step by step. What
will happen to the reading of the mili-ammeter during this?
…………………………………………………………………………………………………………..
(iii) By using the knowledge that you obtained from (c)(i),
(ii) draw a possible graph that sows the variation of the
reading of the ammeter(I) with the reading of the
voltmeter(V). (Take the reading of the volt meter in the
question (c)(i) as positive and the reading of the
voltmeter in the question (c)(ii) as negative)
(iv) If the brightness of the light source S is increased, draw the graph that you will obtain in (c)(i) in the above
axis comparing with the previous graph and label it as M.
(v) If the point at which the curve intersects the voltage axis is given as Vs, plank’s constant is given as h, the
frequency of the blue light ray from the filter is f and the charge of an electron is e, write an expression for the
work function 𝜙 for the material of the cathode.
…………………………………………………………………………………………………………..….........
………………………………………………………............…………………………………………………...
𝐼
𝑉
A B
S Colour filter
mA
V
K
r=0 (
𝐸 𝑅 𝑆
P Q
)
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AL/2019/01/E-II(A)
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Page 23
1
AL/2019/01/E-II(B)
B
A
Part B Essay
05. Consider a train compartment which turns right on the 2𝑚 spaced railway track. A train compartment contains 5 set
of wheels. Total mass of a train compartment is 40tons including 5set of wheels. Following diagram shows the
decreasing in radius of train wheels when considering the wheels from inside to outside. An axis is rigidly hinged at
the center of wheels 𝐴,𝐵.
(a)
i. When train compartment travels in a straight track, effective diameter of the wheel is 0.4𝑚 . If train
compartment travels at 36𝑘𝑚ℎ−1 on straight track, find the angular velocity of the wheels?
ii. If total weight of compartment is distributed equally on all wheels, find the reaction on a wheel given by track.
(b)
i. Copy the above diagram on answer sheet and mark the forces acting on wheels 𝐴,𝐵 given by railway track
when train compartment turns right on the track. (Neglect the frictional forces at the contacts).
ii. What happens to the length of the spring which is attached to the wheel B during turning right as shown?
B
A
600
B
A
2m
m
Right Side turning bend
Page 24
2
AL/2019/01/E-II(B)
(c) Consider an instance when compartment turns right on the track with the radius of 10𝑚 to center of mass of
compartment and at a translational speed 36𝑘𝑚ℎ−1.( take angular velocity of wheels calculated in (a)(ii)
remains unchanged during this motion).
i. Find the translational speeds of wheels𝐴,𝐵.
ii. State how wheels 𝐴,𝐵 can have different values for translational speed even they don‟t change their
angular velocity about its axis.
iii. While turning, what happens to the reaction on wheels 𝐴,𝐵 given by track?
iv. While turning, find the horizontal component of forces act on a wheel set.
(d) When compartment comes back to straight track after turning in bend, train compartment performs many
oscillations before it comes to steady state. This oscillation is called as “hunting oscillation”.
i. State a solution to reduce this hunting oscillation.
ii. A statement states compartment cannot turn in bend perfectly if wheels of compartment designed in
circular thick disc shape. Do you agree with the statement? Reason out this.
06.
(a) When sound travels through from air to medium , one part of sound energy is reflected at the surface.
Remaining part is refracted through that material. In this refraction, certain amount of sound energy is absorbed
by that material. Remaining sound energy travels to another medium.
Absorption coefficient is the quantity used in the calculations related to sound reflection. Absorption coefficient is
defined as 𝛼 =𝐼
𝐼0 .It depends on the frequency of sound energy and medium. The average value of 𝛼 for
various frequencies is called as NRC value.
For the calculations relates with the loss of sound energy TL (Transmission loss), STC are used.𝑇𝐿 is defined
as 𝑇𝐿 = 𝑊0 −𝑊1. The value of 𝑇𝐿 depends on frequency of sound, nature of material, thickness of material and
etc. 𝑆𝑇𝐶 value is the average value of 𝑇𝐿 of different frequencies.
Sound wave of 120𝑑𝐵 sound intensity level is produced from one side of a wall. On the other side of wall, sound
intensity level of 110𝑑𝐵 is sensed by sound sensor. It is given that wall has the value of absorption coefficient
0.3 for that considered frequency. Take the threshold intensity as 𝐼′ = 1 × 10−12𝑊𝑚−2.
Sound
intensity
Sound
intensity level
Incident sound 𝐼0 𝑊0
Sound which travels to the medium by
refraction without reflection
𝐼 𝑊
Sound which travels to another
medium after refraction
𝐼1 𝑊1
Page 25
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AL/2019/01/E-II(B)
i. Find the 𝑇𝐿 value of the wall in 𝑑𝐵 for the corresponding frequency.
ii. . Find the intensity of sound wave which is refracted in the surface of wall without reflection.
iii. . Find the sound intensity of sound wave which is reflected in surface of wall.
iv. . Find the sound intensity of sound wave which is absorbed by material of the wall.
v. The following table shows the NRC, STC values of materials A,B which are used in the construction of
wall.
In the following instances which material would you select
from A, B?
a. for the construction of wall in auditorium as to reduce
the echo effect.
b. for the construction of wall in secret room for meeting
related with safety.
vi. Show that 𝑇𝐿 = 10 log10 𝐼0
𝐼1 from the expression given for 𝑇𝐿
In the construction of building using materials with suitable NRC, STC values, we can reduce the noises and echo
effect. Nowadays electronic circuits are used to reduce the noise in sound instruments.
(b) For all the questions under part b, assume that amic records the wave pattern, amplitude of the produced wave
without any changes.
When a sound wave is produced in front of mic, the mic is unable to sense the produced sound wave only.
Mic senses the resultant wave obtained due to the overlapping of environmental noise.Assume that fig (2)
represents the noise in environment. Fig (1) represents the sound wave produced by man. The wave patterns
represented by fig (1), fig (2) have amplitude of 5a,a respectively and have same frequency.
Nowadays we can record sound in our mobile phone without noise. For this purpose, two mic are used. Mic 1 is
near to the human mouth. It records the resultant wave obtained after the overlapping of environmental noise. Mic 2
records the environmental noise.
Electronic circuit totally changes the recorded sound signal obtained from mic 2 to the opposite phase. Finally, the
resultant sound signal obtained here is made to overlap with the sound signal recorded from mic 1. When the man
produces the sound in the wave pattern shown in fig (1),
Substance NRC STC
A 0.8 50
B 0.6 72
5a
t
5a
x
Figure (1)
t a
x
Figure (2)
Page 26
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AL/2019/01/E-II(B)
i. Draw the wave pattern which is sensed by mic 1(denote the
amplitude)
ii. Draw the wave pattern which is sensed by mic 2 and wave
pattern of phase changed sound. (Denote the amplitude)
iii. Draw the final wave pattern produced by the electronic
circuit.
iv. If accidently a man speaks in front of mic 2 instead of mic
1, draw the wave pattern obtained by electronic circuit
finally. (Denote the amplitude)
07.
(a)
i. State Poiseiulle‟s equation with usual notation.
ii. When a fluid flows through a horizontal tube at volume rate Q,if the pressure difference between the
ends is ∆P, thepower p of a fluidis given by p= ∆PQ. Show that it is dimensionally correct.
iii. With the two relationships in the above questions, show that power loss when fluid flows through
mentioned tube is directly proportional to the second power of rate of volume flow (𝑝 ∝ 𝑄2).
(b) In the system of water supply of a small city, initially water is purified from a water source and then supplied to
the city water center through a tube (tube AB). Finally water is distributed to the city from city water supply
center.Let consider the inner radius of tube AB is 20cm, its length is 100km and 1. .5 × 105𝑃𝑎Pressure should
bemaintainedalways at point B. BC=20km.
Let consider the coefficient of viscosity of water at the average temperature of city 20𝑂𝐶 is 1 × 10−3𝑃𝑎𝑠 and
𝜋 = 3. Following table shows the use of water per day in the city.
period Rate of flow of water
Peak period 6 hours 1.5𝑚3𝑠−1
Off Peak period 18 hours 0.3𝑚3𝑠−1
i. Find the pressure difference that should be maintained across tube AB in peak period.
ii. Find the pressure at part C of tube in peak period.
iii. Find the pressure difference that should be maintained across tube AB in off-peak period.
iv. Find the ratio of power loss due to viscos forces in crowded period and off-peak period.
Water purification center
city water supply center efu ePu;toq;fy; ikak;
A B C
MIC 1
MIC 2
EU
Electronic Unit
Page 27
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AL/2019/01/E-II(B)
v. Radius of tube is reduced by 10% due to the improper removal of hardness water by water purification
center. Due to this effect, as to maintain the same flow of water, by how much times that applied pressure
difference should be increased.
(c) There is necessity of more powerful pumps for the supply of water in peak crowded period and its cost is also
high. As to reduce the above problems, water towers are used in the system of water supply. Consider that water
tower is constructedhereat C. In the off-peak period, water is filled in water tower, at the same time in peak
period, the functioning of pumps are stopped and water supply is conducted with the help of towers.
i. If water tower contains water for one day use in the city, find the volume capacity water tower.
ii. Find the minimum height of water tower to give the needed pressure differences for the supply of water from
C to B at the rate stated in (b) above in the peak period. (Take the density of water as 1000𝑘𝑔𝑚−3 )
iii. Due to the continuous water supply, water level in water tank is reduced by 2m.Find the reduction
percentage in the rate of water supply.
(d) For the above use, instead of 20cm radius pipe, two parallel pipes are connected with same total cross sectional
area. Mention whether the pressure difference calculated in (b) above would increase or decreasein this method.
08.
(a)
i. Write the expression for the electric field intensity and electric potential around point charge +𝑄 at the
distance 𝑟
ii. By considering suitable Gaussian surface, show that the electric field intensity between uniformly charged 2
parallel plates is =𝜎
𝜀0 . Here 𝜎 is surface charge density of a plate.
iii. According to Gauss‟ law, show that electric field intensity at distance 𝑟 from long thin conducting wire is
𝐸 =𝜆
2𝜋𝜀0𝑟 . Here𝜆 𝐶𝑚−1is the charge per unit length in wire.
(b) Photocopy machine is one of the machine functions based on electric field concepts. Here a rotating hollow
semiconductor drum is the major part in producing electric copy.
•
Front Face View
25kV
• •
Side View ;
25kV
Page 28
6
AL/2019/01/E-II(B)
i. When switch is closed, if charge per unit length in rod connected with cathode region is 8.34 × 10−7𝐶𝑚−1,
find the potential on inner surface of drum. ( Internal radius of drum is 10cm , potential at distance 𝑟 from long
charged conductor =2.3 𝜆
2𝜋𝜀0log10 𝑟,
2.3
2𝜋𝜀0= 4.13 × 1010𝐶−2𝑁𝑚2 .
ii. If the charge induced on inner and outer surface are equal, find the amount of induced charge on outer surface.
( Let the length of cathode rod is 40𝑐𝑚).
iii. When switch is opened, anode and cathode rods are neutralized and charges on outer surface is distributed
uniformly throughout the outer surface with the help of high external voltage. Draw the electric field lines
found in drum region due to the charges on internal and external surface of drum. Further, find the external
surface charge density of drum.( let internal ,external radius of drum are equal.).
(c) When light falls on drum, outer surface charges start to move along field direction.Sideward movements of
charges are restricted by semiconductor.
i. If small internal, external arc sector of drum can be treated as uniformly charged 2 parallel plates, find the
potential difference between drum internal and external surfaces. (Thickness of drum is (2𝑚𝑚).
ii. Resistance of this semiconductor is nearly zero in the presence of light and very high at the absence of light.
Variation of intensity of light, falling on small considered sector given below. Draw the graph of variation of
potential difference acrossthis semiconductor with time.
iii. Charges on the drum cannot be affected by the dark region in the paper to be copied. Due to this, an electric
copy is produced by the charges on external surface. This electric copy is further annexed with toner ink in
the basis of charges. What charge element toner ink should have for this process?
Semiconductor which can prevent the movement of free charges •
Light Falling Part
•
Semiconductor
V0
V0
Page 29
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AL/2019/01/E-II(B)
iv. Drum surface cannot absorb ink due to its property. Ink transferred to the drum in above process has to be
transferred to a new white paper as letters in the basis of charges. What charge element white paper should
have for this process?
v. After taking copy of paper, a powerful bulb is lit around drum. What is the reason for this?
09. Answer either Part(A) or Part(B) only
(A) Electric eel which is an aquatic living creature produces current in its body by biochemical method. In its body,
three organs such as Sach‟s organ, Main organ and Hunter‟s organ are able to produce current. Main organ and
Hunter‟s organ are able to produce electric pulses with high potential difference. By this, they get protection from
enemies and grab prey by making them lose consciousness/ making them die. Sach‟s organ produces electric
pulses with low potential difference. By this, it communicates and able to know location.
The special type cells in the organs which produce current are called as electrocytes. When these cells are at rest,
inside the cell, Potassium ions (K+) are in high concentration and Sodium ions (Na
+) are in low concentration.
Outside the cell, Sodium ions (Na +
) are in high concentration and Potassium ions (K +
) are in low concentration.
With these, considerable amount of negative ions are also there inside and outside the cell. When the cell is at rest,
the cell membrane does not allow ions to enter. So, because of the difference in the ion concentrations inside and
outside the cell,the inside of the cell membrane is in negative potential relative to outside. The structure of ions
when the electrocyte cell is at rest, is given in in figure (1). The polarity of the cell is given in figure (2).
When the nerve impulse which produces the electric pulse reaches the cells from the brain, the ion canals in the
cell membrane open. The ions are transferred across the cell membrane through this. The Na+ions which are in
higher amount outside the cell, enter into the cell through one side of cell membrane. So, negative ions are higher
outside the cell membrane and Na+ions are higher in the inside of the cell membrane. After entering of Na
+ions
through the one side of cell membrane, K+ ions which are in higher amount inside the cell exit through the other
side of the cell membrane to keep the ionic equilibrium of the cell. So, higher amount of negative ions are in the
inside and K+ions are in the outside of the other side of the cell membrane. It is called as „active state‟.
Figure(1)
Na+ Na
+ Na+
K+
Na+ Na
+ K+
Na+
K+ K
+ Na
+ K
+ K
+
Na+
Na+
Cell membrane
Cell membrane
Figure(2)
Page 30
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AL/2019/01/E-II(B)
The movement of ions when the nerve impulses are obtained is shown in figure (3) and the polarity of the cell in
active state is shown in figure (4).
After obtaining nerve impulses, because of changing of polarity of the cell membrane, all cells are considered as
batteries connected in series. In active state, the head part of the electric eel is positive end and the tail part of the
electric eel is negative end.
The real values are altered to make the calculations easier.
Assume that 10 electrocyte cell columns which are parallel to one another are in the body of electric eel and in
each column, there are 500 electrocyte cells. Consider that the resultant electromotive force produced by one cell
in active state is 0.15 V and its internal resistance is 0.25Ω. The electric pulses produced by electric eel would
persist for an average time of 2 ms. Assume that the resultant resistance of external aquatic environment is
500 Ω.
1. Give two organs in the body of electric eel which can produce electric pulses with high potential difference.
2. Give two reasons why electric eel produces electric pulses with low potential difference.
3. What is the number of electrocyte cells in the body of an electric eel?
4. What is the internal resistance of the electrocyte cells in the body of an electric eel?
5. What is the highest resultant electromotive force produced in the body of electric eel when electrocyte cell is
in active state?
6. What is the current produced when the electric circuit with the aquatic environment is completed? (assume
that the current goes through the electrocyte cells only in the body of electric eel)
7. What is the potential difference given to the external aquatic environment of the electric eel?
8. What is the energy released to the external aquatic environment when producing one electric pulse as above
said?
9. If the electric eel produces an electric pulse when it is in the real states given below, draw the electric field
lines in the aquatic environment? (Copy the given figures in the answer sheet and draw the electric field lines)
Figure (a)
Figure(b)
10. When searching for prey, electric eel bends its body and surrounds the prey as shown in the figure 10 (d)
above. Give reasons for this.
Figure(3)
K+
Na+ Na
+ Na+
K+
K+
Na+
K+
K+
Na+
K+
Na+
Na+
Na+ Na
+ Na+ Na
+ Na+
K+
Cell membrane
Cell membrane Figure(4)
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(B)
(a) A part of the circuit which changes the
binary numbers in base two to decimal
numbers in base ten is shown in the figure
given below.
I1, I2, I3are the inputs to binary numbers. 0
can be given as inputs by connecting the
switches to earth according to the structure in
figure (1). 1 can be given as inputs by
connecting the switches to +1V. The output
obtained in V0 is connected to another circuit
and forms on the screen in decimal number
form(x) by the process 𝑥 =𝑉0
−1
(1) What is the type of amplifier?
(2) Find the magnitude of R1 if 1 is formed on the screen when I1 is only connected to +1V?
(3) Find the magnitude of R2 if 3 is formed on the screen when I1 and I2are only connected to +1V?
(4) When the binary number 110two is given as input (I2 and I3 are only connected to +1V)
a. What is the obtained V0?
b. What is the decimal number formed on the screen?
(5) If the input should be given for the decimal number 13, (13ten = 1101two)
a. How many more inputs should be connected?
b. What is the magnitude of resistance that can be seen in new inputs?
(6) When enough inputs are connected, can we obtain decimal number 16 on screen? Give reasons.
(16ten = 1000two)
(b) The electronic circuit of non-contact electric tester is given the figure below. It can be confirmed that the
current goes by observing the red light of LED when it is brought near the current passing coated electric wire.
When the red colour LED used here is in function, there will be a 2V potential drop. Current gain of the
transistors used here is 200. Assume that 0.7V is required to forward bias the base-emitter junction of Si
transistor.
I1 I2 I3
20k 5k R2
-
+
R1
+15V
-15V
VO
+1V
50µA
9V
220Ω
T3
T2
T1
; Antena
Very high resistance
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When the antenna of the tester is brought near to the electric wire, current of 50𝜇𝐴 goes through base in transistor
T3 because of the induced electromotive force in the antenna.
i. What is the current (IC) through the resistance of collector in T3?
ii. What is the potential difference (VCB) between the base-collector when T3 is in function?
iii. Give on advantage and disadvantage by using non-contact electric tester?
10. Answer either Part(A) or Part(B) only
(A) 4-stroke engine functions through 4 steps such as intake, compression, combustion, exhaust.
During the intake process, pressure is decreased by the downward movement of piston due to this, valve is opened
and air fuel mixture is intaken. Further, due to the upward motion of piston, air mixture is compressed to high
temperature. At this instant, air mixture is ignited using a small electric spark. Due to the high pressure produced
in ignition process, piston is pushed downwardly. Further, when piston again moves upwardly, exhaustion valve is
opened and combusted air molecules are removed. At the same time, cylinder is ready to perform another cycle.
During the above motion of piston, crankshaft which is connected with piston performs rotational motion. Air-fuel
mixture can be considered as ideal for the following calculations.
(1) Volume of fully expanded air mixture is 200 cm3 and volume of fully compressed air mixture is 20 cm
3.
Intaken air mixture is at 8 x 104 Pa pressure and 27
OC temperature. If fully compressed air mixture reaches
327o C temperature, what is the pressure of fully compressed air mixture?
(2) When this compressed air mixture is ignited, temperature of mixture suddenly increases to 15270C and
number of moles of air mixture increases by 25%. By considering the volume of air mixture is unchanged
(20cm3), find the instant pressure of combusted air mixture.
(3) When combusted air is fully expanded, temperature of air mixture drops to 6270C. Find the pressure of fully
expanded combusted air mixture.
(4)
i. If the average pressure of air mixture after the expansion of combusted air is 3.15 MPa, calculate the
work done by air (W1) at this instance.
ii. Further, if the average pressure of air mixture when piston moves upwardly is 1.5 MPa, calculate the
work done on air (W2) at this instance.
iii. When piston completes one cycle, find the net work done by the air mixture (W).
Intake Compressio
n
Exhaust Combusti
on
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iv. Efficiency of engine (e) is defined as e= 𝑊
𝑄× 100. Here W is net work done by air mixture and Q is
the energy produced in one combustion process of air-fuel mixture.
1. If the efficiency of this engine is 40%, find the energy produced in one combustion of air-
fuel mixture.
2. If the ignition heat of fuel is 4x104 Jg
-1, find the mass of fuel burnt in each cycle.
v. A vehicle with above type engine travels at a uniform speed in a straight road. At this instance,
piston functions at a constant rate of 3000 rpm. For this one hour motion, find the volume of fuel
needed (density of fuel is 1005kgm-3
).
vi. When vehicle is worked as mentioned in (4) (v.), the surface temperature of engine cover is found to
be 3000C. This is not suitable for engine. So, to remove the heat from engine cover surface
effectively, parallel plates made of same material as engine cover is fixed perpendicular to engine
cover surface in order to increase the total surface area. If the engine cover temperature has to be
maintained at 2500C, by which percentage the surface area should be increased? (Environmental
temperature is 300C).
(B)
(a) Write the expression for the radiation energy E emitted by a
perfect black body with the surface area A and surface
temperature T K in unit time. (𝜎- Stephen‟s constant).
(b) Following graph shows the variation of energy of photons
emitted from unit surface in unit time from a star with surface
temperature 2x104 K with those photon wavelengths. By
considering the star as a perfect blackbody, answer the
following questions. For the calculations,let = 3.
i. By using Wien‟s displacement law, find the 𝜆m marked on the graph. (Wien‟s constant=3x10-3
mK).
ii. Find the frequency of photon emitted at high intensity.
iii. Find the area enclosed by given curve with x axis. (𝜎 = 5.7x10-8
Wm-2
K-4
).
iv. 4𝐻 → 𝐻𝑒 + 2𝑒+ + neutrons + energy
Hydrogen fusion reaction takes place inside the star‟s core region due to its high pressure and high
temperature. Hydrogen fusion reaction takes place according to the above equation. This energy
produced in the nuclear reaction goes to the star surface and emitted from the surface.
1. If mass of a hydrogen nucleus is 1.67 × 10−27𝑘𝑔 and mass of the helium nucleus is
6.65 × 10−27𝑘𝑔 by considering that the mass of positrons and neutrons are negligible, find the
mass destroyed in one nuclear fusion reaction.
2. Find the energy released in one nuclear reaction.
3. Due to the above nuclear fusion reaction, it is found 2.1 × 1046 He atoms are produced inside the
star in every year. (Let one year = 3 × 107s). Find the radius of this star.
4. As stated in question (b)(iv)(3), if nuclear fusion reaction is maintained at the same rate, for
which value of star radius the surface temperature of star will take 6000K?
𝜆m
Eλ
𝜆
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(c) Nuclear furnace technology is used to convert energy released in nuclear reaction as our usable energy.
In this process, to transfer the heat energy gained from nuclear reaction in nuclear furnace, generally
melted sodium is used. Due to the unexpected accident at nuclear furnace, unstable sodium isotope is
produced because of the escaped neutron entering sodium nuclei. This involves in nuclear reaction and
turns into stable magnesium atom. Nuclear reaction for this process is given below.
01
2412
2411 MgNa
energy
At a nuclear furnace accident, sodium atoms of mass 2.3 × 106𝑘𝑔 are converted as radioactive sodium
isotopes according to the above nuclear reaction equation. Half life time of this isotope is 15 hours.
i. Find the number of produced 𝑁𝑎1124 isotopic atoms.
ii. Find the decay constant of isotope 𝑁𝑎1124 in 𝑠−1.
iii. Find the initial radioactivity of isotope 𝑁𝑎1124 in this nuclear furnace.
iv. Find the 𝛽 ray emission rate after 60 hours of isotopic formation.
NanNa 2411
10
2311
