Blue print for sample paper 2
UNITS
VSA
SA1
SA2
2(1)
-
Electrostatics
1(1)
Current
electricity
Magnetic effect
of current and
magnetism
E.M.I and A.C
1(1)
E.M.W
1(1)
2(1)
Optics
1(1)
2(1)
Dual nature of
matter
Atoms and
nuclei
Electronics
1(1)
Communication
system
Total
1(1)
4(2)
1(1)
1(1)
Total
5(1)
8(3)
7(3)
3(1)
8(3)
4(1)
8(4)
3(2)
6(2)
5(1)
14(5)
3(1)
4(2)
3(1)
6(3)
2(1)
8(8)
LA
6(2)
3(1)
2(1)
Value based
question
5(1)
2(1)
3(1)
16(8)
27(9)
7(2)
5(2)
4(1)
15(3)
70(29)
GROUP: S.N.BOSE
KENDRIYA VIDYALAYA SANGATHAN
GUWAHATI REGION
SUBJECT : PHYSICS
Class-XII
General instructions-.
(a)
(b)
(c)
(d)
(e)
All questions are compulsory
There are 29 questions in total. Q. 1 to 8carry1 mark each. Q. 9 to 16 carry 2 marks each,
Q. 17 to 25 carry 3 marks each , Q. 26 carry 04 marks and Q.27 to 29 carry 5 marks each.
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.
Use of calculators is not permitted.
You may use the following physical constants wherever necessary.
c = 3 x 108 ms-1
h = 6.6 x 10-34Js
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.Name the physical quantity whose S.I unit is J/C. Is it a scalar or a vector quantity?
2. A beam of α particles projected along x -axis, experiences a force due to a magnetic field
along the y -axis. What is the direction of the magnetic field?
3. A glass lens of refractive index 1.45disappears when immersed in a liquid. What is the value
of refractive index of the liquid?
4. What is the ratio of radii of the orbits corresponding to first excited state and ground state in a
hydrogen atom?
5. Name the characteristics of E M waves that (i) increases , (ii) remains constant
in the EM spectrum as one moves from radiowave region towards ultraviolet region.
6. The stopping potential in an experiment on photoelectric effect is 1.5 volt. What is the
maximum K.E of the photoelectrons emitted?
7. The power factor of an a.c. is 0.5.What will be the phase difference between voltage and
current in this circuit?
8. State the condition in which terminal voltage across a secondary cell is equal to its e.m.f.
9.For an amplitude modulated wave, the maximum amplitude is found to be 10v while the
minimum amplitude is 2v. Calculate the modulation index. Why modulation index is generally
kept less than one?
10. The energy of the electron in the ground state of H atom is -13.6 eV
a) What does the –ve sign signify?
b) How much energy is required to take an electron in this atom from the ground state to the first
excited state?
11. Show that in a uniform electric field, a dipole experiences a torque but no net force. Derive
an expression for torque.
12. An α particle and a proton moving with the same speed enter the same magnetic field region
at right angles to the direction of the field. Find the ratio of the radii of the circular paths which
the two particles may describe.
13. Two long coaxial solenoids of the same length but different number of turns are wound one
over the other. Deduce the expression for the mutual inductance of this arrangement.
14. Define resolving power of a microscope. How is this affected when the wave length of
illuminating radiations is decreased?
15. Suppose the electric field part of an E.M.W in vacuum is
E= 3.1N/c Cos (1.8rad/m)y +(5.4*106rad/s)t)i
16.What is the wavelength?
Write an expression for magnetic field part of the wave.
17. Show how a NAND gate can be used as OR gate.
18. Derive the expression for force per unit length between two straight parallel current carrying
conductors. Hence define one Ampere.
OR
Explain the principle and working of a cyclotron with the help of a schematic diagram. Write the
expression for cyclotron frequency.
19. a) State briefly any two reasons explaining the need for modulating a signal.
b) Draw a labeled block diagram of a simple modulator for obtaining an AM signal.
20. Define the terms i) drift velocity ii) relaxation time.
A conductor of length L is connected to a DC source of e.m.f E. If this conductor is replaced by
another conductor of same material and same area of cross section but of length 3L, how will the
drift velocity change?
21. Give the principle of potentiometer. A potentiometer wire of length 10 meter has a resistance
of 10 ohm. It is connected to a cell of e.m.f 2 volt and internal resistance 1 ohm. Calculate the
length of the balance point for a cell of e.m.f 1.5 volt.
22. Half life of a certain radioactive material againstdecay is 138 days. After what lapse of time
the undecayed fraction of the material will be 6.25%.
23. Draw the graphs showing the variation of photoelectric current with the anode potential of a
photocell for i) the same frequencies but different intensities I1>I2>I3 of incident radiation, ii) the
same intensities but different frequencies ν1 > ν2> ν3 of incident radiation. Explain why the
saturation current is independent of the anode potential.
24. A beam of light converges to a point P. Now a lens is placed in the path of the convergent
beams 12 cm from P. At what point does the beam converge if the lens is a a) convex lens of
focal length 20 cm, b)a concave lens of focal length 16 cm?
25. My friend and I have been assigned a work to choose a step down transformer for supply of
power for a small town with a demand of 1 MW at 220V situated 20km away from an electric
plant generates power at 440V; the resistance of the two line wires carrying power is 0.5ohm/km;
two step down transformers are available- 4000V-220V & 100000V – 220V. Your friend has
chosen 100000V-220V step down transformer.
a) As a student of physics, which step down transformer will you prefer for supply of a
power for a small town. Give reason.
b) What are the values associated with the above decision?
(ANS: a) I go with my friends’ option, because Power loss is less in 100000V-220V
that is why Transmission of a.c over long distances is preferred for transmission.(hints:
Iv=P/ Ev, P=I2R,Power loss=output power/input power*100) b ) Knowledge is useful only
when put to practice and concern for country’s welfare.
26. State Huygens principle. Using the geometrical construction of secondary wavelets ,explain
the refraction of a plane wave front incident at a plane surface. Hence verify snells law of
refraction.
27. Explain the phenomenon of diffraction of light at a single slit, to show the formation of
diffraction fringes. Show graphically the variation of the intensity, with angle, in this single slit
diffraction pattern.
Or
Prove that –μ1/u+ μ2/v= μ2- μ1/RWhen refraction occurs from rarer to denser media at a convex
refracting spherical surface.
How will the focal length of a lens be affected if it is dipped in water?
28.(a)What is a Zener diode ? With a circuit diagram explain how a zener diode can be used as a
voltage regulator.
(b) Write the truth table for the combination of gates as shown below:
A
B
C
Or
Draw the circuit diagram of a base biased n-p-n transistor in C-E configuration. Explain how this
circuit is used to obtain transfer characteristics. How do we explain the working of a transistor as
a switch using the characteristic?
29. Find the expression for the capacitance of a parallel plate capacitor of area A and plate
separation d if i) a dielectric slab of thickness t, and ii) a metallic slab of thickness t, where (t<d)
are introduced one by one between the plates of the capacitor. In which case would the
capacitance be more and why?
Or
Define electric flux. What is its unit? Show that the electric field intensity at the surface of a
charged conductor is given by E=σ/Єo n ,where σ is the surface charge density and n is a unit
vector normal to the surface in the outward direction.
Sample paper 2
Marking - Scheme
1. Electric potential
Scalar
½mark
½mark
2. Z -axis
1 mark
3. 1.45
1 mark
4. formula
½mark
Result-
1/2mark
5. frequency increases and speed remains constant
½+1/2 mark
6. 1.5 ev
1 mark
7. cos φ = 0.5 and φ = 600
1 marks
8. E=v+Ir
1 mark
r=0
1mark
9. 0.2
1 mark
Reason
1 mark
10. Significance
1 mark
10.2 ev
1 mark
11. Net force=o
1 mark
Derivation-
1 mark
12. Formula of radius-
½ mark
Calculation-
1 mark
Correct Ans-
1/2 mark
13.Derivation-
1 mark
Final expression-
1 mark
14. Defination-
1mark
Formula-
1/2 mark
15.Resolving power increases-
1/2 mark
16. 2π/λ=1.8
½ mark
C=E/B
½ mark
Expression-
1mark
17. combination-
1mark
Truth table-
1 mark
18. Derivation-
2 mark
Definition-
1mark
19. Two needs
(1+1) mark
Block diagram
1mark
20. Defination-
(1+1) mark
Calculation-
1mark
21.Principle-
1mark
Calculation-
1mark
Result-
1mark
22.Formula-
1 mark
Calculation-
1mark
Result-
1 mark
23. Two graphs-
(1+1)mark
Explanation-
1mark
24. Formula-
1mark
V=7.5cm
1mark
V=48cm
1mark
25. (ANS: a) I go with my friends’ option, because Power loss is less in 100000V-220V
that is why Transmission of a.c over long distances is preferred for transmission.(hints: Iv=P/ Ev,
P=I2R,Power loss=output power/input power*100) b ) Knowledge is useful only when put to
practice and concern for country’s welfare
(3+1)mark
26.Principle
1mark
Ray diagram
1 mark
Derivation
1mark
27.Defination-
1mark
Ray diagram-
1mark
Derivation-
2mark
Angular width-
1mark
Or
Derivation-
4mark
Focal length-increase-
1mark
28.correct statement
½ mark
circuitdiagram-
1 mark
explanation
1+1/2 mark
Correct truth table
2marks
Or
Circuit diagram-
1mark
Graph-
1mark
Explanation-
3marks
29-Derivation with dielectric slab-
2.5mark
Derivation with conducting slabOr
DefinitionUnitDerivation-
2.5mark
1mark
1mark
3 marks