Download NAVODAYA VIDYALAYA SAMITI : NEW DELHI

SET - 1
HSB COACHING CENTRE
9210846949
www.hsbsolutions.jimdo.com
SAMPLE PAPER - V
PHYSICS FOR CLASS XII
General Instructions:
(a) All questions are compulsory
(b) There are 30 questions in total. Qns. 1 to 8 carry 1 mark each. Qns. 9 to 18 carry 2 marks
each, Qns. 19 to 27 carry 3 mark each and Qns. 28 to 30 carry 5 marks each.
(c) There is no overall choice. However, an internal choice has been provided in one question of
2 marks, one question of 3 marks and all three questions of 5 marks each. You have to attempt
only one of the given choices in such questions.
(d) Use of calculators is not permitted.
(e) You may use the following physical constants wherever necessary.
c = 3 x 108 ms-1
h = 6.6 x 10-34 Js
e = 1.6 x 10-19C
µo = 4π x 10-7 TmA-1
1/4πεo = 9 x 109 N m2C-2
Avogadro number
NA = 6.023 x 1023 mol-1
Mass of the neutron = 1.675 x 10-27 kg
Boltzmann constant, k = 1.38 x 1023 J K-1
1
In each of the diodes shown, forward resistance is 50 Ω. Then find current
through the 100 Ω resistor in the given circuit.
150 Ω
D1
50 Ω
D2
6V
100 Ω
2
3
4
5
A convex lens and a concave lens of same focal length are combined in contact.
What would be the resulting focal length?
What orientation will a freely suspended magnetic needle have at (i) geographic
south and (ii) magnetic south pole of the earth?
What is the power factor of a pure inductor?
Compare the velocities of X – rays of wavelength 1 Ả and red light of wave
length 6000 Ả in vacuum.
6
In photo electric emission from the surface of a metal, when the wave length of
incident light is λ, the maximum kinetic energy of photo electron is E and the
number of emitted electrons is N. If now the intensity is doubled, keeping λ
fixed, what will be the effect on kinetic energy and number of photo electrons
emitted?
7 Calculate the ratio of energy of electron in the fourth and fifth orbits of hydrogen
atom.
8 Why is the base region of transistor thin and lightly doped ?
9 A 80 µF capacitor is charged by a 50 V battery. The capacitor is disconnected
from the battery and then connected across another uncharged 320 µF capacitor.
Calculate the charge on the second capacitor.
10 A potential difference V is applied to a copper wire of diameter D and length l.
What is the effect on the drift velocity of electrons when:
(i)
doubling V (ii) doubling l (iii) doubling D?
11 For what value of unknown resistance X, the current flowing through the
galvanometer would be zero in the circuit shown below.
1Ω
6Ω
6Ω
B
G
X
1Ω
1Ω
6Ω
A
C
D
1Ω
12 State Ampere’s circuital law in magnetism and use it to find the magnetic field
inside a current carrying toroidal solenoid.
13 The reactance of an inductor is 20 Ω. What does it mean? What would be its
reactance, if the frequency of the a c is doubled? What opposition does the
inductor offer to the flow of a d c?
14 State Lenz’s law in electromagnetic induction and explain how it supports law of
conservation of energy.
15 Which part of the electromagnetic radiation:
(i)
is used for satellite communication
(ii)
has is frequency range 4 x 1014 Hz to 7 x 1014 Hz
(iii)
produce intense heating effect
(iv)
used for purification of water.
16 An equiconvex lens has a power of 5 D. If it is made of glass of refractive index
1.5, calculate the radius of curvature of each surface.
OR
Draw a labelled ray diagram of an astronomical telescope used in the normal
adjustment position.
Two astronomical telescopes T1 and T2 have the same magnifying power. The
ratio of aperture of their objectives is 3:2. Which one of these two produces
image of greater intensity?
17 When a deuteron of mass 2.0141 u and negligible kinetic energy is absorbed by
a lithium (3Li6) nucleus of mass 6.0155 u, the compound nucleus disintegrates
spontaneously into two alpha particles, each of mass 4.0026 u. Calculate the
energy in joules carried by each alpha particle. ( 1 u = 1.66 x 10-27 kg)
18 Give reasons for the following:
(i)
Long distance radio broadcasts use short-wave bands.
(ii)
Satellites are used for long distance TV transmission.
19 A metallic square loop ABCD of size 15cm and negligible resistance is moved at
a uniform velocity of v m/s in a uniform magnetic field of 2T. The field lines
being normal to the plane of the paper. The loop is connected to an electrical
network of resistances each of resistance 2 Ω. Calculate the speed of the loop for
which 2mA current flows in the loop.
20 An electric kettle has two windings. When one of them is switched on , the water
begins to boil in 15 min. and other is switched on in 30 min.
In how much
time will the water in the kettle begin to boil if the two windings are switched on
(i) in series (ii) in parallel.
21 A large vessel is filled with a liquid of dielectric constant k. Two vertical plates
touch the liquid. The dimensions of plates are a and b ,the distance between them
is d. The plates have been charged by applying the voltage V 0 and then
disconnected from the source. To what height will the liquid rise.
22 Three charges -2µC , +22µ
-2µ
as shown in the fig. Calculate the total electric field intensity due to all these
three charges at point P.
P
1m
A
-2µC
B
1m
22µC
C
-2µC
1m
23 The lens combination of three lenses L1 and L2 and L3 shown in the fig. forms an
image at 30 cm to the right of the lens L3 . The focal lengths of lenses L1 and L2
are 10 cm and -10 cm respectively. What is the focal length of lens L3.
24 What changes will occur in the focal length of a (i) concave mirror and (ii)
convex lens when the incident violet light is replaced with red light. Give reason.
25 What is the de-Broglie wavelength of an electron in an atom at absolute
temperature T K.
The wavelength λ of a photon and de-Broglie wavelength of an electron have
the same value. Show that energy of photon is
2mc
times the kinetic energy of
h
electron.
26 state radioactive decay law and establish the relation between decay constant and
half life period of a radio active substance.
OR
Write the nuclear decay equations for:
(i)
α – decay of 88 Ra 226
(ii) α – decay of 94 Pu 242
(iii)
β- – decay of 15 P 32
(iv) β- – decay of 83 Bi 210
(v)
β+ – decay of 6 C 11
(vi) β+ – decay of 43 Tc 97
27 Define the term Modulation . Name three different type of modulations used for
a message signal, using sinusoidal continuous carrier wave. Explain the meaning
of any one of these.
28 Explain the method of obtaining a n – type semiconductor from a sample of
intrinsic semi conductor. Draw the energy band diagram of the n – type semi
conductor.
A semiconductor has equal electron and hole concentration of 6 x 10 8/m3. On
doping with certain impurity, electron concentration increases to 9 x 1012/m3.
(i)
Identify the new semiconductor obtained after doping.
(ii)
Calculate the new hole concentration.
OR
What is an AND gate? Write its truth table and Boolean expression for its
output. Draw the logic symbol
With the help of a neat circuit diagram, explain the realization of an AND gate
using semiconductor diodes.
Write the truth table for the following combination of four NOR gates arranged
as shown in figure.
A
B
Y
29 With the help of a suitable diagram, describe Young’s double slit experiment for
obtaining interference pattern. Write an expression for the fringe width of the
pattern. Represent graphically the variation of intensity in the pattern.
What will be the effect on interference fringes obtained in Young’s double slit
experiment, if
(i)
source of light of longer wavelength is used
(ii) distance between two slits be increased to larger extent
(iii) two slits are illuminated by different sources of light of same λ
(iv) if the distance of the source and the double slit is increased?
OR
Differentiate between plane polarized and un polarized light. Describe a method
to get a plane polarized light by reflection.
Discuss the intensity of transmitted light when a polaroid sheet is rotated
between two crossed polaroids?
What is the Brewster angle for air to glass transition? (Refractive index of
glass=√3.)
30 Two circular coils X and Y having radii R and R/2 respectively are placed in
horizontal plane with their centres coinciding with each other. Coil X has a
current I flowing through it in the clockwise sense. What must be the current in
coil Y to make the total magnetic field at the common centre of the two coils,
zero?
With the above currents flowing in the two coils, if the coil Y is now lifted
vertically upwards through a distance R, what would be the net magnetic field at
the centre of coil Y?
OR
Define current sensitivity and voltage sensitivity of a moving coil galvanometer.
Two moving coil meters, M1 and M2 have the following particulars:
R1 = 10 Ω, N1 = 30, A1 = 3.6 × 10–3 m2, B1 = 0.25 T
R2 = 14 Ω, N2 = 42, A2 = 1.8 × 10–3 m2, B2 = 0.50 T
(The spring constants are identical for the two meters). Determine the ratio of
(a) current sensitivity and (b) voltage sensitivity of M2 and M1.
How can a galvanometer be converted into (i) an ammeter and (ii) a voltmeter of
required range?
*******************************************