SIROHI CLASSES PH-9810272244/9810252244/34 Page 1 : / Series SKS 1 Code No. 55/1/1 Candidates must write the Code on the title page of the answer-book. R.No. Please check that this question paper contains 6 printed pages. Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. Please check that this question paper contains 26 questions. Please write down the Serial Number of the question before attempting it. 15 minutes time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. PHYSICS (Theory) Time allowed : 3 hours Maximum Marks : 70 General Instructions 1. All questions are compulsory. There are 26 questions in all. 2. This question paper has five sections: Section A, Section B, Section C, Section D and Section E. 3. Section A contains five questions of one mark each, Section B contains five questions of two marks each, Section C contains twelve questions of three marks each, Section D contains one value based question of four marks and Section E contains three questions of five marks each. 4. There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all the three questions of five marks weightage. You have to attempt only one of the choices in such questions. 5. You may use the following values of physical constants wherever necessary. c = 3 × 10 8 m/s h = 6.63 × 10 –34 Js e = 1.6 × 10 –19 C μ o = 4×10 –7 T m A –1 0 = 8.854 × 10 –12 C 2 N –1 m –2 0 1 4 9 10 9 N m 2 C –2 m e = 9.1 10 –31 kg mass of neutron = 1.675 × 10 –27 kg mass of proton = 1.673 × 10 –27 kg Avogadro Numbers = 6.023 ×10 23 per gram mole Boltzmann constant = 1.38 × 10 –23 JK –1
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SIROHI CLASSES PH-9810272244/9810252244/34 Page 1
: /Series SKS 1 Code No. 55/1/1
Candidates must write the Code on
the title page of the answer-book. R.No.
Please check that this question paper contains 6 printed pages.
Code number given on the right hand side of the question paper should be written on the
title page of the answer-book by the candidate.
Please check that this question paper contains 26 questions.
Please write down the Serial Number of the question before attempting it.
15 minutes time has been allotted to read this question paper. The question paper will be
distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only
and will not write any answer on the answer-book during this period.
PHYSICS (Theory)
Time allowed : 3 hours Maximum Marks : 70
General Instructions
1. All questions are compulsory. There are 26 questions in all.
2. This question paper has five sections: Section A, Section B, Section C, Section D and
Section E.
3. Section A contains five questions of one mark each, Section B contains five questions of two
marks each, Section C contains twelve questions of three marks each, Section D contains one
value based question of four marks and Section E contains three questions of five marks
each.
4. There is no overall choice. However, an internal choice has been provided in one question of
two marks, one question of three marks and all the three questions of five marks weightage.
You have to attempt only one of the choices in such questions.
5. You may use the following values of physical constants wherever necessary.
c = 3 × 108 m/s
h = 6.63 × 10–34
Js
e = 1.6 × 10–19
C
µo = 4 ×10–7
T m A–1
0 = 8.854 × 10–12
C2 N
–1 m
–2
0
1
4 9 10
9 N m
2 C
–2
me = 9.1 10–31
kg
mass of neutron = 1.675 × 10–27
kg
mass of proton = 1.673 × 10–27
kg
Avogadro Numbers = 6.023 ×1023
per gram mole
Boltzmann constant = 1.38 × 10–23
JK–1
SIROHI CLASSES PH-9810272244/9810252244/34 Page 2
Section A ( 5×1= 5 Marks)
1) Name the physical quantity having unit V-m. Is it scalar or vector? (1)
2) The compass needle , pivoted about the horizontal axis and free to move in the magnetic
meridian ,is observed to point along the
a) Vertical direction at a place A
b) Horizontal direction at a place B
give the value of angle of dip at these two places . (1)
3) Why long distance radio broadcasts use short wave band ? (1)
4) A wavefront AB passing through a system C emerges as DE. Name the system C. (1)
5) A point charge Q is placed at point O as shown in the figure. Is the potential difference VA – VB
positive, negative or zero, if Q is (a) positive (b) negative? (1)
Section B (5×2= 10 Marks)
6) (a)The given network has two cells of emf's E1 and E2 and two resistances R1 and R2 . The
ammeter A reads zero. What would the voltmeter V read ?
(b) Name the conservation law related to Kirchhoff’s junction rule .
The adjoining figure shows part of electrical circuit. Compute i . (2)
SIROHI CLASSES PH-9810272244/9810252244/34 Page 3
7) In a Young's double slit experiment, the intensity at a point where the path difference is
6
( , being the wave-length of the light used) is I If I0 denotes the maximum intensity, Find
0
I
I.
(2)
8) A nucleus of mass M. initially at rest splits into two fragments of masses '
3
Mand
2 '( ')
3
MM M . Find the ratio of de-Broglie wavelengths of the two fragments. (2)
OR
Calculate the ratio of de-Broglie wavelengths associated with a deutron moving with velocity 2v and
an alpha particle moving with velocity v.
9) At a point due to a point-charge, the electric field intensity and potential are 32 N C –1
and
16 JC–1
respectively. Calculate : (i) the distance of the charge from the point of observation, and
(ii) magnitude of the charge. (2)
10) In the potentiometer circuit shown in Fig. , the balance (null) point is at X. State with reason,
where the balance point will be shifted when
i) resistance R is increased, keeping all parameters unchanged.
ii) resistance S is increased, keeping R constant. (2)
Section C (12×3 = 36 Marks)
11) State the theorem which relates the enclosed charge, inside a closed surface. with the electric flux
through it. Use this theorem to obtain the electric field due to a uniformly charged thin spherical
shell at an (i) outside point (ii) inside point. (3)
12) Two monochromatic beams A and B of equal intensity I, hit a screen . The number of photons
hitting the screen by beam A is twice that by beam B Then , when inference can you make about
their frequencies. (3)
13) The output of an unregulated dc power supply needs to the regulated. Name the device that can be
used for this purpose and draw the relevant circuit diagram. (3)
14) A cell of emf (E) and internal resistance (r) is connected across a variable external resistance (R).
Plot graphs to show variation of (i) E with R, (ii) Terminal p.d. of the cell (V) with R. (3)
SIROHI CLASSES PH-9810272244/9810252244/34 Page 4
15) Name the regions of E.M. Spectrum in which Lyman and Paschen series lies. If 1 and 2 are
the wavelengths of the first members of the Lyman and Paschen series respectively, then find
1 : 2. (3)
16) What is Brewster’s Law ? The polarising angle of a transparent medium is 60°. Determine (i) the
refractive index of the medium, (ii) the refracting angle. (3)
17) State the underline principle of a cyclotron. Give its limitations and two practical uses. (3)
18) Define the terms (i) disintegration constant and (ii) half-life for a radioactive nucleus. obtain the
relation between the two. (3)
19) A beam of light converges to a point P. A lens is placed in the path of the convergent beam 12 cm
from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20
cm, and (b) a concave lens of focal length 16 cm ? (3)
OR
A converging lens which has a focal length of 20 cm is placed 60 cm to the left of a concave
mirror of focal length 30 cm. An object is placed 40 cm to the left of the lens. Find the position,
nature and magnification of the final image.
20) What is meant by detection of a signal in a communication system? With the help of a block
diagram explain the detection of A.M. signal. (3)
21) A parallel plate capacitor, each with plate area A and separation d, is charged to a potential
difference V. The battery used to charge it is then disconnected. A dielectric slab of thickness d
and dielectric constant K is now placed between the plates. What change, if any will take place in
a) charge on the plate
b) electric field intensity between the plates
c) capacitance of the capacitor?
Justify your answer in each case. (3)
22) (a) What are electromagnetic waves ? A plane electromagnetic wave travels in vacuum along
z-direction. What can you say about the directions of its electric and magnetic field vectors? If the
frequency of the wave is 30 MHz, what is its wavelength?
(b) What is displacement current ? A variable frequency AC source is connected to a capacitor .
How will the displacement current change with decrease in frequency ? (3)
Section D ( 1×4 = 4 Marks)
23) Ritu saw her aunt suffering from severe joint pain. Her aunt could not take any pain killer as she
was allergic to them. Ritu in her quest to help her aunt found the use of magnets. She read Dr.
Philpott’s work on magnetic therapy, that most people are negative magnetic field deficient due to
electromagnetic pollution. Supplementing the body with negative field energy has shown to
SIROHI CLASSES PH-9810272244/9810252244/34 Page 5
restore balance and encourage healing. Ritu takes her aunt to the doctor daily without fail for the
treatment. Her aunt is improving at a phenomenal speed.
i) What values does Ritu have?
ii) A (hypothetical) bar magnet (AB) is cut into two equal parts. One part is now kept over
the other, so that pole C2 is above C1. If M is the magnetic moment of the original
magnet, what would be the magnetic moment of the combination so formed ? (4)
Section E (3×5 = 15 Marks)
24) State the principle of a step-up transformer. Explain, with the help of a labelled diagram, its
working.
Describe briefly any two energy losses, giving the reasons for their occurrence in actual
transformers. How these losses can be minimised ?
How is the transformer used in large scale transmission and distribution of electrical energy over
long distance? (5)
OR
(a) In a series LCR circuit, the voltages across an inductor, a capacitor and a resistor are 30 V, 30
V and 60 V respectively. What is the phase difference between the applied voltage and the current
in the circuit?
(b) In the following circuit, calculate
(i) the capacitance 'C' of the capacitor, if the power factor of the circuit is unity, and
(ii) also calculate the Q-factor of the circuit.
25) Draw a circuit diagram to study the input and output characteristics of a n-p-n transistor in its
common -emitter configuration . Draw the typical input characteristics and explain how these
graphs and used to calculate
a) Input resistance
b) Output resistance and
SIROHI CLASSES PH-9810272244/9810252244/34 Page 6
c) Current amplification factor of the transistor. (5)
OR
(a) If the resistance Ri is increased (see figure.), how will the readings of the ammeter and
voltmeter change?
(b) (i) Two car garages have a common gate which needs to open automatically when a car
enters either of the garages or cars enter in both. Devise a circuit that resembles this situation.
Give truth table also.
(ii)The truth table of logic gate has the form given here. Name this gate and draw its symbol.
26) Draw the labelled ray diagram for the formation of image by an astronomical telescope. Derive
the expression for its magnifying power in normal adjustment. Write two basic features which can
distinguish between a telescope and a compound microscope. (5)
OR
(a) Draw a ray diagram for the formation of image by a compound microscope.
Define its magnifying power. Deduce the expression for the magnifying power of the microscope.
(b) Explain
( i) Why must both the object and the eyepiece of a compound microscope have short focal
lengths?
( i i) While viewing through a compound microscope, why should our eyes be positioned not
on the eyepiece but a short distance away from it for best viewing?
SIROHI CLASSES PH-9810272244/9810252244/34 Page 7
SOLUTIONS
1) Name the physical quantity having unit V-m. Is it scalar or vector? (1)
SOL: Electric Flux . It is scalar.
2) The compass needle , pivoted about the horizontal axis and free to move in the magnetic
meridian ,is observed to point along the
a) Vertical direction at a place A
b) Horizontal direction at a place B
give the value of angle of dip at these two places . (1)
SOL: (a) Angle of dip at A is 900 . (b) Angle of dip at B is 0
0 .
3) Why long distance radio broadcasts use short wave bands ? (1)
SOL: This is because ionosphere reflects waves in these band.
4) A wavefront AB passing through a system C emerges as DE. Name the system C. (1)
SOL: A prism.
5) A point charge Q is placed at point O as shown in the figure. Is the potential difference VA –
VB positive, negative or zero, if Q is (a) positive (b) negative? (1)
SOL: Let the distance of points A and B from charge Q be rA and rB respectively.
Potential difference between points A and B
VA - VB depends on the nature of charge Q.
(a)VA – VB is positive when Q > 0.
(b)VA – VB is negative when Q < 0.
6) a)The given network has two cells of emf's E1 and E2 and two resistances R1 and R2 . The
ammeter A reads zero. What would the voltmeter V read ? (1)
SIROHI CLASSES PH-9810272244/9810252244/34 Page 8
SOL: No current is being drawn from the cell E2 . The voltmeter will read the emf E2 of this cell.
b) Name the conservation law related to Kirchhoff’s junction rule .
The adjoining figure shows part of electrical circuit. Compute i . (1)
SOL: Conservation of charge . 1 A.
7) In a Young's double slit experiment, the intensity at a point where the path difference is
6
( , being the wave-length of the light used) is I If I0 denotes the maximum intensity, Find
0
I
I. (2)
SOL:
8) A nucleus of mass M initially at rest splits into two fragments of masses '
3
Mand
2 '( ')
3
MM M . Find the ratio of de-Broglie wavelengths of the two fragments. (2)
SOL: h
p
From law of conservation of linear momentum
SIROHI CLASSES PH-9810272244/9810252244/34 Page 9
Ratio 1 : 1
OR
Calculate the ratio of de-Broglie wavelengths associated with a deutron moving with velocity 2v
and an alpha particle moving with velocity v.
SOL:
1
2
1 2
1 2
2 2 4
4 4
v v
v v
p m m
p m m
p p
Ratio 1 : 1
9) At a point due to a point-charge, the electric field intensity and potential are 32 N C –1
and
16 JC–1
respectively. Calculate : (i) the distance of the charge from the point of observation,
and (ii) magnitude of the charge. (2)
SOL:
= 0.88×10
–9 C
10) In the potentiometer circuit shown in Fig. , the balance (null) point is at X. State with
reason, where the balance point will be shifted when
i) resistance R is increased, keeping all parameters unchanged.
ii) resistance S is increased, keeping R constant. (2)
SOL: (i) When R is increased, the current from the driver cell is decreased. This decreases the
potential gradient. So, the balance point will shift to the right.
(ii) Increasing resistance S shall have no effect on balance point. This is because there will be no
flow of current in this branch when the potentiometer is balanced.
11) State the theorem which relates the enclosed charge, inside a closed surface. with the electric
flux through it. Use this theorem to obtain the electric field due to a uniformly charged thin
spherical shell at an (i) outside point (ii) inside point. (3)