#

Series : YWX5Z/5 SET ~ 1

-
Roll No. Q.P. Code 55/5/1
- -
-
Candidates must write the Q.P. Code
on the title page of the answer-book.

^m¡{VH$ {dkmZ (g¡ÕmpÝVH$)

PHYSICS (Theory)
3 70
Time allowed : 3 hours Maximum Marks : 70

/ NOTE #
(I) - 27
Please check that this question paper contains 27 printed pages.
(II) - - - -

Q.P. Code given on the right hand side of the question paper should be
written on the title page of the answer-book by the candidate.
(III) - 33
Please check that this question paper contains 33 questions.
(IV) , -
Please write down the Serial Number of the question in the
answer-book at the given place before attempting it.
(V) - 15 -
10.15 10.15 10.30 -
-
15 minute 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 candidates will read the question paper only and will not
write any answer on the answer-book during this period.

55/5/1 Page 1 of 27 P.T.O.

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(i) - 33
(ii) - , , ,
(iii) 1 16 1
(iv) 17 21 - 2

(v) 22 28 - 3
(vi) 29 30 - 4
(vii) 31 33 - 5
(viii) - ,

(ix) -
(x)

c=3 108 m/s

h = 6.63 10 34 Js
e = 1.6 10 19 C

0=4 10 7 T m A 1

0 = 8.854 10 12 C2 N 1 m 2

=9 109 N m2 C 2

(me) = 9.1 10 31 kg

= 1.675 10 27 kg

= 1.673 10 27 kg

= 6.023 1023

= 1.38 10 23 JK 1

55/5/1 Page 2 of 27
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General Instructions :
Read the following instructions carefully and follow them :
(i) This question paper contains 33 questions. All questions are compulsory.
(ii) This question paper is divided into five sections Sections A, B, C, D and E.
(iii) In Section A Questions no. 1 to 16 are Multiple Choice type questions. Each
question carries 1 mark.
(iv) In Section B Questions no. 17 to 21 are Very Short Answer type questions.
Each question carries 2 marks.
(v) In Section C Questions no. 22 to 28 are Short Answer type questions. Each
question carries 3 marks.
(vi) In Section D Questions no. 29 and 30 are case study-based questions. Each
question carries 4 marks.
(vii) In Section E Questions no. 31 to 33 are Long Answer type questions. Each
question carries 5 marks.
(viii) There is no overall choice given in the question paper. However, an internal
choice has been provided in few questions in all the Sections except Section A.
(ix) Kindly note that there is a separate question paper for Visually Impaired
candidates.
(x) Use of calculators is not allowed.
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

0 =4 10 7 T m A 1

0 = 8.854 10 12 C2 N 1 m 2

=9 109 N m2 C 2

Mass of electron (me) = 9.1 10 31 kg

Mass of neutron = 1.675 10 27 kg

Mass of proton = 1.673 10 27 kg
6.023 1023 per gram mole
Boltzmann constant = 1.38 10 23 JK 1

55/5/1 Page 3 of 27 P.T.O.

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1. C
: ,

(A) C (B) C
(C) C (D)

2. - = ,

r -

(A) (B)

(C) (D)

3. R K
K A B

(A) 4R (B)

(C) (D)

4. 10 kV , 106 ms 1
0·4 T

B
(A) 2·5 cm (B) 5 cm
(C) 8 cm (D) 10 cm
55/5/1 Page 4 of 27
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SECTION A
1. A metal sheet is inserted between the plates of a parallel plate capacitor
of capacitance C. If the sheet partly occupies the space between the
plates, the capacitance :
(A) remains C (B) becomes greater than C
(C) becomes less than C (D) becomes zero

2. The electric field at a point in a region is given by = where is

a constant and r is the distance of the point from the origin. The

magnitude of potential of the point is :

(A) (B)

(C) (D)

3. Four resistors, each of resistance R and a key K are connected as shown

in the figure. The equivalent resistance between points A and B when key
K is open, will be :

(A) 4R (B)

(C) (D)

4. A charged particle gains a speed of 106 ms 1, when accelerated from rest

through a potential difference 10 kV. It enters a region of magnetic field
of 0·4 T such that . The radius of circular path described by it is :
(A) 2·5 cm (B) 5 cm
(C) 8 cm (D) 10 cm
55/5/1 Page 5 of 27 P.T.O.
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5. 14 cm A

(A) 0·019 Am2 (B) 0·14 Am2

(C) 0·196 Am2 (D) 0·615 Am2

6. t = (8t2 + 5t + 7)
, t Wb t = 4s
(emf )
(A) 32 V (B) 37 V
(C) 64 V (D) 69 V

7. , -
?
(A) (B)
(C) UV (D)

8. ( ) 1 ,
0 1 1 0 2 2
(A) [M L T ] (B) [M L T ]
1 2 2 1 1 1
(C) [M L T ] (D) [M L T ]

9. - - ?

(A) X- (B) AM

(C) (D) TV

10. fo fe

(A) fo fe fe > fo (B) fo fe fo > fe

(C) fo fe fe > fo (D) fo fe fo > fe

55/5/1 Page 6 of 27
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5. A current of A is maintained in a circular loop of radius 14 cm. The

value of dipole moment associated with the loop is :

(A) 0·019 Am2 (B) 0·14 Am2
(C) 0·196 Am2 (D) 0·615 Am2

6. The magnetic flux linked with a coil changes with time t as

= (8t2 + 5t + 7), where t is in seconds and is in Wb. The value of emf
induced in the coil at t = 4 s is :
(A) 32 V (B) 37 V
(C) 64 V (D) 69 V

7. Which of the following rays coming from the Sun plays an important role

(A) Infrared rays (B) rays

(C) UV rays (D) Visible light rays

8. The dimensions of ( ) 1, where is permittivity and is permeability of

a medium, are :
0 1 1 0 2 2
(A) [M L T ] (B) [M L T ]
1 2 2 1 1 1
(C) [M L T ] (D) [M L T ]

9. Which of the following electromagnetic waves has photons of largest

momentum ?
(A) X-rays (B) AM radio waves
(C) Microwaves (D) TV waves

10. A compound microscope has an objective and an eyepiece of focal lengths

fo and fe, respectively. To obtain a large magnification of a small object,
the microscope should have :
(A) fo and fe small, and fe > fo (B) fo and fe small, and fo > fe
(C) fo and fe large, and fe > fo (D) fo and fe large, and fo > fe
55/5/1 Page 7 of 27 P.T.O.
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11. ,

?
(A) 0 2a2 (B) 0 4a2
(C) a2 2a2 (D) 2a2 4a2

12.

(A) (B)

(C) (D)

13 16 (A) (R)
(A) (R) (A),
(B), (C) (D)
(A) (A) (R) (R), (A)

(B) (A) (R) , (R), (A)

(C) (A) , (R)

(D) (A) (R)

13. (A) p- Si

(R) p-

14. (A)

(R)

55/5/1 Page 8 of 27
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11. Two coherent light waves, each having amplitude a , superpose to

produce an interference pattern on a screen. The intensity of light as seen
on the screen varies between :
(A) 0 and 2a2 (B) 0 and 4a2
(C) a2 and 2a2 (D) 2a2 and 4a2

12. The kinetic energy of an alpha particle is four times the kinetic energy of

a proton. The ratio of de Broglie wavelengths associated with them

will be :

(A) (B)

(C) (D)

Questions number 13 to 16 are Assertion (A) and Reason (R) type questions. Two
statements are given one labelled Assertion (A) and the other labelled Reason
(R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the
correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not
the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Both Assertion (A) and Reason (R) are false.

13. Assertion (A) : The impurities in p-type Si are not pentavalent atoms.
Reason (R) : The hole density in valance band in p-type semiconductor
is almost equal to the acceptor density.

14. Assertion (A) : During formation of a nucleus, the mass defect produced
is the source of the binding energy of the nucleus.
Reason (R) : For all nuclei, the value of binding energy per nucleon
increases with mass number.

55/5/1 Page 9 of 27 P.T.O.

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15. (A)

(R)

16. (A)

(R) 10 5

17. 3·6 1014 Hz 6·8 1014 Hz

- 2

18. ( n (< 4) , R
R/3
2

( Io
, /3 , 2

19. 1000 25 V 250 V

? 2

20.

MeV : 2
235
m 92
U = 235·04393 u, m = 139·92164 u

94
m 38 Sr = 93·91536 u, = 1·00866 u

1 u = 931 MeV/c2

55/5/1 Page 10 of 27
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15. Assertion (A) : The Balmer series in hydrogen atom spectrum is formed
when the electron jumps from higher energy state to the
ground state.
Reason (R) :
between successive orbits only.
16. Assertion (A) :
presence of only few alpha particles at angle of scattering
led him to the discovery of nucleus.
Reason (R) : The size of nucleus is approximately 10 5 times the size of
an atom and therefore only few alpha particles are
rebounded.

SECTION B
17. The threshold frequency for a given metal is 3·6 1014 Hz. If
monochromatic radiations of frequency 6·8 1014 Hz are incident on this
metal, find the cut-off potential for the photoelectrons. 2
18. (a) A point object is placed in air at a distance R/3 in front of a convex
surface of radius of curvature R, separating air from a medium of
refractive index n (< 4). Find the nature and position of the image
formed. 2
OR
(b) -up, the intensity of the
central maximum is Io. Calculate the intensity at a point where the
path difference between two interfering waves is /3. 2
19. A voltmeter of resistance 1000 can measure up to 25 V. How will you
convert it so that it can read up to 250 V ? 2
140 94
20. When a neutron collides with , the nucleus gives 54 Xe and 38 Sr
as fission products and two neutrons are ejected. Calculate the mass
defect and the energy released (in MeV) in the process. Given : 2

m = 235·04393 u, m = 139·92164 u

m = 93·91536 u, = 1·00866 u

1 u = 931 MeV/c2

55/5/1 Page 11 of 27 P.T.O.

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21. 25 C 10·0 125 C 10·5
(i) , (ii) 425 C 2

22. ( T=0K , -
- - ?

( IV
3

23. A d
, , K

(a) (b)
3

24. 1·0 mm 1·0 m

500 nm 600 nm
3

55/5/1 Page 12 of 27
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21. The resistance of a wire at 25 C is 10·0 . When heated to 125 C, its

resistance becomes 10·5 . Find (i) the temperature coefficient of
resistance of the wire, and (ii) the resistance of the wire at 425 C. 2

SECTION C

22. (a) Draw the energy-band diagrams for conductors, semiconductors

and insulators at T = 0 K. How is an electron-hole pair formed in a
semiconductor at room temperature ?
(b) Carbon and silicon both, are members of IV group of periodic table
and have the same lattice structure. Carbon is an insulator
whereas silicon is a semiconductor. Explain. 3

23. A parallel plate capacitor has plate area A and plate separation d. Half of
the space between the plates is filled with a material of dielectric
constant K in two ways as shown in the figure.

(a) (b)

Find the values of the capacitance of the capacitors in the two cases. 3

24.
1·0 mm and the screen is 1·0 m away from the slits. A beam of light
consisting of two wavelengths 500 nm and 600 nm is used to obtain
interference fringes. Calculate : 3
(a) the distance between the first maxima for the two wavelengths.
(b) the least distance from the central maximum, where the bright
fringes due to both the wavelengths coincide.

55/5/1 Page 13 of 27 P.T.O.

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25. -
3

26. m e

( ( )

( , = 3

27. ABCD 1·5

1·25 AB i
AD i
3

28. ( A B R 2R
2 3 , -
A B 3

55/5/1 Page 14 of 27
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25. Differentiate between half-wave and full-wave rectification. With the

help of a circuit diagram, explain the working of a full-wave rectifier. 3

26. An electron of mass m and charge e is revolving anticlockwise around

the nucleus of an atom.

(a) Obtain the expression for the magnetic dipole moment ( ) of the
atom.

(b) If is the angular momentum of electron, show that

= . 3

27. A rectangular glass slab ABCD (refractive index 1·5) is surrounded by a

transparent liquid (refractive index 1·25) as shown in the figure. A ray of
light is incident on face AB at an angle i such that it is refracted out
grazing the face AD. Find the value of angle i. 3

28. (a) Two small solid metal balls A and B of radii R and 2R having
charge densities 2 and 3 respectively are kept far apart. Find the
charge densities on A and B after they are connected by a
conducting wire. 3

OR

55/5/1 Page 15 of 27 P.T.O.

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( , - - d

- 3

29 30 -

29.

-
1791

-
, - -

NBAI = k
N=
A= -
B=
k=
=

55/5/1 Page 16 of 27
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(b)
apart, parallel to each other, as shown in the figure. They are
uniformly charged having charge densities and respectively.

electric field is zero and identify the region in which it lies. 3

SECTION D
Questions number 29 and 30 are Case Study-based questions. Read the following
paragraphs and answer the questions that follow.

29. A galvanometer is an instrument used to show the direction and strength

of the current passing through it. In a galvanometer, a coil placed in a
magnetic field experiences a torque and hence gets deflected when a
current passes through it. The name is derived from the surname of
Italian scientist L. Galvani, who in 1791 discovered that electric current

counter torque.
In equilibrium, the deflecting torque is balanced by the restoring torque
of the spring and we have :
NBAI = k
where N is the total number of turns in the coil
A is the area of cross-section of each turn
B is the radial magnetic field
k is the torsional constant of the spring
is the angular deflection of the coil

55/5/1 Page 17 of 27 P.T.O.

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(Ig)

,
,

(i) 1

(A) (B)

(C) (D)

(ii) 6 0·2 A
(0 5 A)
1
(A) 0·25 (B) 0·30
(C) 0·50 (D) 6·0
(iii) (ii) 1
(A) 0·20 (B) 0·24
(C) 6·0 (D) 6·25
(iv) ( ) R1 (0 V)
R1 R2
, (0 2 V)
1
(A) (R2 2R1) (B) (R2 R1)
(C) (R1 + R2) (D) (R1 2R2)

( ) 5 mA 100
- 18 cm2 0·20 T
- 1

(A) 3·6 10 3 Nm (B) 1·8 10 4 Nm

(C) 2·4 10 3 Nm (D) 1·2 10 4 Nm

55/5/1 Page 18 of 27
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As the current (Ig) which produces full scale deflection in the
galvanometer is very small, the galvanometer cannot as such be used to
measure current in electric circuits. A small resistance, called shunt, of a
suitable value is connected with the galvanometer to convert it into an
ammeter of desired range. By using a higher resistance, a galvanometer
can also be converted into a voltmeter.
(i) The value of the current sensitivity of a galvanometer is given by : 1

(A) (B)

(C) (D)

(ii) A galvanometer of resistance 6 shows full scale deflection for a

current of 0·2 A. The value of shunt to be used with this
galvanometer to convert it into an ammeter of range (0 5 A) is : 1
(A) 0·25 (B) 0·30
(C) 0·50 (D) 6·0
(iii) The value of resistance of the ammeter in case (ii) will be : 1
(A) 0·20 (B) 0·24
(C) 6·0 (D) 6·25
(iv) (a) A galvanometer is converted into a voltmeter of range
(0 V) by connecting with it, a resistance R1. If R1 is
replaced by R2, the range becomes (0 2 V). The resistance
of the galvanometer is : 1
(A) (R2 2R1) (B) (R2 R1)
(C) (R1 + R2) (D) (R1 2R2)

OR
(b) A current of 5 mA flows through a galvanometer. Its coil has
100 turns, each of area of cross-section 18 cm2 and is
suspended in a magnetic field 0·20 T. The deflecting torque
acting on the coil will be : 1
(A) 3·6 10 3 Nm (B) 1·8 10 4 Nm
(C) 2·4 10 3 Nm (D) 1·2 10 4 Nm
55/5/1 Page 19 of 27 P.T.O.
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30. ,
, -
hv , v h

hv
,

(i) - - I
? 1

(A) (B)

(C) (D)

(ii) ,
1
(A)
(B)
(C)
(D)

(iii)
? 1
(A) -
(B) -
(C)
(D)

55/5/1 Page 20 of 27
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30.
theory, where light travels in the form of small bundles of energy called
photons. The energy of each photon is hv, where v is the frequency of

beam of light determines the intensity of the incident light. A photon

incident on a metal surface transfers its total energy hv to a free electron
in the metal. A part of this energy is used in ejecting the electron from
the metal and is called its work function. The rest of the energy is carried
by the ejected electron as its kinetic energy.

(i) Which of the following graphs shows the variation of photoelectric

current I with the intensity of light ? 1

(A) (B)

(C) (D)

(ii) When the frequency of the incident light is increased without

changing its intensity, the saturation current : 1
(A) increases linearly
(B) decreases
(C) increases non-linearly
(D) remains the same

(iii) Which of the following graphs can be used to obtain the value of
1
(A) Photocurrent versus Intensity of incident light
(B) Photocurrent versus Frequency of incident light
(C) Cut-off potential versus Frequency of incident light
(D) Cut-off potential versus Intensity of incident light

55/5/1 Page 21 of 27 P.T.O.

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(iv) ( ) ,
K R, K Y KB -
1
(A) KR > KY > KB (B) KY > KB > KR
(C) KB > KY > KR (D) KR > KB > KY

( ) - -
? 1
(A) (B)
(C) (D)

31. ( (i) E1, E2 E3 (emf )

(4 V, 2 ), (2 V, 4 ) (6 V, 2 ) ,
E1, E2 E3

(ii) ,
R (= 10 ) , A B

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(iv) (a) Red light, yellow light and blue light of the same intensity
are incident on a metal surface successively. KR, KY and KB
represent the maximum kinetic energy of photoelectrons
respectively, then : 1
(A) KR > KY > KB (B) KY > KB > KR
(C) KB > KY > KR (D) KR > KB > KY
OR
(b) Which of the following metals exhibits photoelectric effect
with visible light ? 1
(A) Caesium (B) Zinc
(C) Cadmium (D) Magnesium
SECTION E
31. (a) (i) Three batteries E1, E2 and E3 of emfs and internal
resistances (4 V, 2 ), (2 V, 4 ) and (6 V, 2 ) respectively
are connected as shown in the figure. Find the values of the
currents passing through batteries E1, E2 and E3.

(ii) The ends of six wires, each of resistance R (= 10 ) are joined

as shown in the figure. The points A and B of the
arrangement are connected in a circuit. Find the value of the
effective resistance offered by it to the circuit. 5

OR

55/5/1 Page 23 of 27 P.T.O.

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( (i) I (= 1 A) -
(n = 8·5 1028 m 3)
A B - 1·0 10 7 m2
2·0 10 7 m2

(I) A B -
(II) B

(ii) q1 (= 16 C) q2 (= 1 C) = (3 m)

= (4 m) = (3 m) + (4 m) -
5

32. ( (i) - - L
I

(ii) 10 mH 20 mH -

(I) (emf )

(II) 5

( (i)

(ii) 40 s 2A
5 mV (emf ) t = 10 s
5
55/5/1 Page 24 of 27
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(b) (i) Current I (= 1 A) is passing through a copper rod

(n = 8·5 1028 m 3) of varying cross-sections as shown in the
figure. The areas of cross-section at points A and B along its
length are 1·0 10 7 m2 and 2·0 10 7 m2 respectively.
Calculate :

(I) the ratio of electric fields at points A and B.

(II) the drift velocity of free electrons at point B.
(ii) Two point charges q1 (= 16 C) and q2(= 1 C) are placed at

points = (3 m) and = (4 m) . Find the net electric

field at point = (3 m) + (4 m) . 5

32. (a) (i) Define self-inductance of a coil. Derive the expression for the
energy required to build up a current I in a coil of
self-inductance L.
(ii) The currents passing through two inductors of
self-inductances 10 mH and 20 mH increase with time at the
same rate.
Draw graphs showing the variation of :
(I) the magnitude of emf induced with the rate of change
of current in each inductor.
(II) the energy stored in each inductor with the current
flowing through it. 5
OR
(b) (i) Define the term mutual inductance. Deduce the expression
for the mutual inductance of two long coaxial solenoids of the
same length having different radii and different number of
turns.
(ii) The current through an inductor is uniformly increased from
zero to 2 A in 40 s. An emf of 5 mV is induced during this
period. Find the flux linked with the inductor at t = 10 s. 5
55/5/1 Page 25 of 27 P.T.O.
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33. ( (i)

(ii)
50 102 cm
5

( (i)

(ii) R
n1 n2

55/5/1 Page 26 of 27
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33. (a) (i) Draw a ray diagram of a reflecting telescope (Cassegrain)

and explain the formation of image. State two important
advantages that a reflecting telescope has over a refracting
telescope.
(ii) In a refracting telescope, the focal length of the objective is
50 times the focal length of the eyepiece. When the final
image is formed at infinity, the length of the tube is 102 cm.
Find the focal lengths of the two lenses. 5
OR
(b) (i) Write any two advantages of a compound microscope over a
simple microscope. Draw a ray diagram for the image
formation at the near point by a compound microscope and
explain it.
(ii) A thin planoconcave lens with its curved face of radius of
curvature R is made of glass of refractive index n1. It is
placed coaxially in contact with a thin equiconvex lens of
same radius of curvature of refractive index n2. Obtain the
power of the combination lens. 5

55/5/1 Page 27 of 27 P.T.O.