Download PRACTICE PAPER

Class XII
Physics Theory
Units
VSA
1 mark
1(1)
Sr.No
1 Electrostatics
2 Current Electricity
3 Magnetic effects of current and
magnetism
4 EMI & AC
5 EM waves
6 Optics
Dual nature of Radiation &
7 matter
8 Atoms & Nuclei
9 Electronic devices
10 Communicational System
1(1)
1(1)
1(2)
1(1)
1(1)
1(1)
8(8)
Blue Print
SA -1
2
marks
2(1)
-
SA -2
3
marks
3(1)
4(2)
2(1)
3(1)
4(2)
2(1)
2(1)
16(8)
LA
5
marks
5(1)
-
4 Mark
4(1)
Total
8(3)
7(2)
3(1)
3(1)
5(1)
5(1)
8(4)
8(3)
3(1)
14(6)
3(1)
3(1)
3(2)
3(1)
27(9)
15(3)
4(2)
6(3)
7(3)
5(2)
70(29)
4(1)
Note : No of questions are given inside the bracket and total marks allotted are
given outside the bracket.
PRACTICE PAPER
CLASS - XII
PHYSICS
Time : 3 Hours
General Instructions :
1.
All questions are compulsory
2.
There are 30 questions in total.
Question 1 to 8 carry one mark each
Questions 9 to 18 carry two marks each
Questions 19 to 27 carry 3 marks each and
Questions 28 to 30 are 5 marks each.
3.
Use of calculators is not permitted.
4.
You may use the following constants wherever necessary.
K = 9x 109 Nm2 C–1
R = Ryd berg constant
M. M : 70
h = 6.63 x 10–34 Js
lev = 1.6 x 10–19 J
1 A0 = 10–10 m
Q1.
An electric dipole of dipole moment 20 x 10 –6 Cm is enclosed by a closed surface
what is the net electric flux coming out of the surface?
Q2.
Why is alloy alnico is preferred for making permanent magnets?
Q3.
A capacitor blocks d.c. and allows a.c why?
Q4.
What is the essential condition for observing a rainbow?
Q5,
What do you understand by normal adjustment of a telescope?
Q6.
Write Einstein's' photoelectric equation.
Q7.
What type of wave front will emerge from (i) a point source and (ii) distant light
source?
Q8.
Why thickness of depletion layer of p-n junction decreases on forward biasing .
Q9.
Derive an expression for electric field intensity at any point on axial line of the
electric dipole.
Q10.(a)
How will you represent a resistance of 3700  10% by colour code?
(b)
Write two special characteristics of manganin due to which it is used in
making standard resistances.
Explain how does the resistivity of a conductor depend upon (i) number density n
of free electrons. (ii) relaxation time t.
Q11. A solenoid of length 0.5m has a radius of 1 cm and is made up of 500 turns. It
carries a current of 5A. What is the magnitude of magnetic field inside the
solenoid.
Q12. Kamla peddles a stationary bicycle. The pedals of which are attached to a 100
turn coil of area 0.10 m . The coil rotates at half a revolution per second and it is
placed in a uniform magnetic field of 0.01 T perpendicular to the axis of rotation of
the coil. What is the maximum voltage generated in the coil ?
Q13. What is total internal reflection of light. Write two essential conditions for total
internal reflection of light to take place at an interface separating two transparent
media.
Q14. The light of wavelength 600 n m is incident normally on a slit of width 3mm.
Calculate the linear width of central maximum on a screen kept 3 m away from
the slit.
Q15. How does the (i) pole strength and (ii) magnetic moment of each part of a bar
magnet change if it is cut into two equal pieces along its length?
Q16. What do you mean by binding energy per nucleon of a nucleus? Draw a graph
showing the variation of binding energy per nucleon with mass number A.
Q17. Derive an expression for the distance upto which the T.V. signals can directly be
received from a T.V. tower a height 'h'.
OR
With the help of a suitable circuit diagram, briefly explain the working of an
amplitude demodulator.
Q18. A woman and her daughter of class XII in KV were in the kitchen, preparing a
feast for visitors using the new microwave oven purchased last evening. Suddenly, the
daughter noticed sparks inside the oven and unplugs the connection after switching it
off. She found that inside the microwave oven a metallic container had been kept to
cook vegetable. She informs her mother that no metallic object must be used while
cooking in microwave oven and explains the reasons for the same.
a) What attitude of the daughter inspires you?
b) Give another use of a microwave oven
c) The frequency of microwave is 3 x 1011 Hz. Calculate its wavelength.
Q19. a)
How can a moving coil galvanometer be converted into an ammeter of given
range.
b)
A galvanometer can be converted into a voltmeter of certain range by
connecting a resistance of 980 in series with it. When the resistance of
470 connected in series, the range is halved. Find the resistance of the
galvanometer.
Q20.(a)Write any four properties of electromagnetic waves.
(b) Draw a plane electromagnetic wave travelling along x-axis.
Q21. a)
What are coherent sources of light?
b) Write the conditions for constructive and destructive interference to take
place.
OR
a)
State Brewster law.
b)
Give any two important uses of polaroids.
Q22. Describe Davisson and Germer experiment to establish the wave nature of
electrons.
Q23. Calculate the energies of the various energy levels of a hydrogen atom and draw
an energy level diagram for it.
Q24. The output of an unregulated d.c power supply is to be regulated.
a). Name the device which can be used for this purpose.
b) How is it represented symbolically ?
c) With the help of a circuit diagram , explain its use as a voltage regulator.
Q25. In the figure below, circuit of a logic gate and input waveform is show.
i)
Name the logic gate.
ii)
Write its truth table
iii)
Give the out put wave form.
A
Input – 'A'
Q26(a).What is modulation?What is the need of modulation in communication systems?
(b)Define modulation index?
Q27. a) What is an equipotential surface?
b) Sketch equipotential surface for a (1) uniform electric field.
(2) two equal positive charges.
c) Show that the amount of work done in moving a test charge over an
equipotential surface is zero.
OR
a)
Derive an expression for the energy stored in a parallel plate capacitor with
air as the medium between its plates.
b)
Find the equivalent capacitance of the combination of capacitors between
the points A and B as shown in the figure.
A
60 F
40 F
60 F
60 F
10 F
60 F
10 F
B
Q28. a)
b)
Using phasor diagram, drive an expression for the impedance of a series
LCR circuit. What do you mean by resonance condition of such a circuit.
Describe the use of a series resonant circuit in the tuning of a radio receiver.
OR
Explain with the help of a labelled diagram, the principle, construction and
working of a transformer. Why is its core laminated?
Q29. Draw a labelled ray diagram to show the formation of an image by a compound
microscope. Derive expression for its magnifying power.
OR
Derive lens maker's formula for a double convex lens. State the assumptions
used and the convention of signs used.
PRACTICE PAPER
MARKING SCHEME
CLASS - XII
PHYSICS
1.
Zero
1
2.
High retentivity, high coercivity.
½+½
3.
. For d.c ,  0, XC = 
½+½
4.
Back of the observer must be towards the sun.
1
5.
Final image is formed at infinity.
1
6.
Kmax = = h – o
1
7.
(i)
Spherical wave front.
½
(ii)
Plane wave front.
½
8. The diffusion of electrons and hoies into the depletion region decreases width of
depletion region
9.
Derivation
Direction of electric field.
10. a) 3700  10% = 3.7 x 102  10%.
Orange, violet, red and silver
1
b) Low temperature coefficient of resistance ,high value of retentivity
1.
1
n
(i)
1
T
(ii)
11.
B=
=
0
0
nI I
N I = 4 x 10–7x 500 x 5
0.5
e
1½
½
= 6.28 x 10–3 T
12.
½
½+1+½
Max.voltage generated=NBAw
=100X0.01X0.10X2X3.14X0.5
1
=0.314V
1/2
13.
14.
Two conditions
½+½
Two applications
½+½
B= 2 D
d
½
–9
=
2x 3x 600 x 10
–3
3 x 10
1
=1.2m
1/2
15.
16.
(i)
Pole strength of each part reduces to half
1
(ii)
Magnetic moment of each part reduces to half
1
Binding energy per nucleon – definition
Graph
17.
½
1½
Diagram
½
Derivation
1½
OR
Diagram
½
Working of amplitude demodulator
18.
(ANS: Presence of mind, Knowledge of subject; b) used in
telecommunication; & c) λ=
19.
1
(a)
1½
/c = (3 x 1011))/ (3 x 108). = 10-3.
Using shunt parallel to moving coil galvanometer
(b) V/R(g)+980=V/2/R(g)+470
R(g)=40 ohm
1+1
20.(a) Four properties of em waves
2
(b)diagram
1
Coherent sources – conditions
21.
(a)
(b)
Condition for constructive interference to take place.
(i)
(iii)
1
Path difference between two superposing waves is an integral
multiple of wavelength .
½
Phase difference between the two superposing waves is an even
multiple of
½
Conditions for destractive interference to take place.
(i)
Phase difference between the two superposing waves is an odd
multiple of .
(ii)
Path difference between the two superposing waves is an odd
multiple of .
½
OR
22.
23.
Statement of Brewster law
1
Two uses of polaroids
2
Labelled diagram.
1
Observations made by Davission & Germer
1
Conclusions.
1
Calculations for energies of various energy levels of a hydrogen atom using the
relation
E=
---13.6/n
square
2
Energy level diagram
24.
1
a) Zener diode
b)Symbol
c)Circuit
½+1/2+2
25.
diagram
(i)
NOT gate
(ii)
Truth Table
In put
Out put
0
1
1
0
,explaination
Input – 'A'
Out put of NOT gate
(iii)
1+1+1
26. (a)definition
.
½
(i)
The height of the antenna should be at leas Wavelenth /4 in length
(ii)
Power rediated , If longer wave lengths are directly radiated into space,
they
die out after covering some distance due to their low power.
(iii)
To
avoid
mixing
up
of
signals
from
different
transmitters.
1+1/2
(b)definition
1
27.
(a) Definition
(b)Sketches
(c)
work
done
1+2+2
OR
28.
(a)
Phasor diagram
1
Derivation of expression for impedence of series LCR circuit.
2
Resonance condition : XL = XC, Z = R
1
Impedence is minimum, current in maximum.
(b)
, By changing value of adjustable capacitor C, the signal from the
desired station can be tuned in
½
OR
29.
Labelled diagram of transformer
1
Principle
1
Construction
1
Working
1
To reduce energy lose due to eddy currents.
1
Labelled ray diagram
2
Expression for its magnifying power
3
OR
Assumptions and sign conventions used.
1
Ray diagram
1
Derivation of Lans maker's formula.
3